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Benfield Conduit Bending Manual, 2nd Edition Copyright © 1980 Penton Media, Inc. All rights reserved FIRST EDITION First printing July July,, 1980 SECOND EDITION First printing October, 1992; Second printing May, 1993; Third printing March, 1994; Fourth printing February, 1995; Fifth printing July, 1995; Sixth printing February, 1996; Seventh printing August, 1997; Eighth printing September, 1998; Ninth printing February, 2000; Tenth printing June, 2001; Eleventh Eleven th printing April, 2004; Twelfth printing September September,, 2004; Thirteenth printing April, 2005; Fourteenth printing April, 2006; Fifteenth printing March, 2007; Sixteenth printing May, 2008; Seventeenth printing May,, 2009; Eighteenth printing, September, 2010; Nineteenth Printing, May 2012. May Published by EC&M Books Overland Park, KS 66212-2215 ecmbooks.com ISBN-10: 0-87288-510-0 ISBN-13: 978-0-87288-510-3 Please Note: The designations “National Electrical Code,” “NE Code,” Code,” and “NEC, “NEC,”” where used in this book refer to the National Electrical Code ®, which is a registered trademark of the National Fire Protection Association.
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Table of Contents
Table of Contents About the Author ......... .................. .................. ................... ................... .................. ................... ................... ................... ................... .................. ............ ... 3 Preface to the First and Second Editions ......... .................. ................... ................... ................... ................... .................. ............ ... 5 Introduction Introduct ion ......... .................. ................... ................... .................. ................... ................... .................. ................... ................... .................. ................... ............ 7 Chapter 1: Bending 90° Stubs ...................... ............................... ................... ................... .................. ................... ................... ............... ...... 9 Chapter 2: All About Offsets......... .................. .................. ................... ................... ................... ................... .................. ................... ............ .. 13 Chapter 3: Back-to-Back Bends ........................... .................................... .................. ................... ................... ................... ............... ..... 18 Chapter 4: Utilizing the "Gain" ............... ........................ ................... ................... ................... ................... .................. ................... ............ .. 21 Chapter 5: Three and Four Saddle Bends .................. ........................... ................... ................... .................. .................. ......... 23 Chapter 6: Bending with Hickeys Variable Radius Bends ................ ......................... ................... ............... ..... 28 Chapter 7: Rolling Offsets (Around Corners) and 90° Compound Belts ...................... ............................... ................... ................... .................. .................. ......... 32 Chapter 8: Keeping Conduit Run "On-the-Flat" at Ceiling Corners and "Over the Top" Top" ......... ................... ................... .................. ................... ............ .. 36 Chapter 9: Electrical Conduit in Concrete Slabs, Shifting EMT Stubs, Etc. ......... .............. ..... 37 Chapter 10: Removing Bend in 1/2" EMT ......... .................. ................... ................... ................... ................... .................. ........... 41 Chapter 11: Bending Surface Metal Molding......... ................... ................... .................. ................... ................... ............. .... 42 Chapter 12: Bending PVC Conduit ..................... ............................... ................... .................. ................... ................... ................ ....... 44 Chapter 13: Using Benfield Formulas and Symbols with "Chicago" Rachet-Type, Rachet-T ype, Hydraulic or Electrically Powered Benders ......... .................. ........... 45 Chapter 14: Hand Bender Types Described......... .................. .................. ................... ................... ................... ............... ..... 47 Chapter 15: A Review of Conduit Bending Tips........ .................. ................... .................. ................... ................... ........... 57 Chapter 16: General Bending Information of Value ................ .......................... ................... ................... ............... ..... 60 Summary .......... ................... .................. ................... ................... ................... ................... .................. ................... ................... .................. ................... ............ .. 67
About the Author
3
About the Author Jack Benfield has been identified with the electrical conduit industry since 1929. He was a pioneer in the marketing of thin wall (EMT) conduit in the U.S.A. Republic Steel Corporation created EMT. To market this brand-new product the company selected six young salesmen to cover the U.S.A. Jack was in that original group of six. It was called the “EMT flying squad.” The Great Depression of the 1930’s made it no “bed of roses” to sell a new untried raceway. Almost every branch of the electrical industry tried to discourage the acceptance of thin wall conduit. • Electricians cussed it, because it was such a problem to bend. Only hickeytype tools were available and they kinked the EMT too easily. • Labor Unions wanted more labor, not less. • The steel mills wanted more tonnage, not less. • The NE Code restricted the use of EMT to exposed dry locations and to circuits of 300 volts, or less. With such a bleak outlook and such code restrictions, those six young salesmen barnstormed from coast to coast. The odds against EMT were overwhelming. “At times we wondered,” Jack says, “if it would ever become an accepted raceway.” Then in the early 30’s a wheel-type EMT bender (hand portable type) with a fixed radius appeared. It did an acceptable job, but it was an awkward tool with four parts and a floppy hook. The need for a better bender was obvious. Jack designed and patented the first one-piece, solid hook Benfield bender for 1/2”, 3/4” and 1” EMT. Sales took off when one-sweep, one-piece benders became available. Jack visited electrical superintendents on construction jobs, all over the free world, and saw a great need for precision in conduit bending. That need triggered Jack into adding such helpful features as painted symbols, the star-point, the arrow, the rim notch, the degree scale, the Zip-Guide for handles and a simple formula for offsets and saddles. Jack Benfield wrote the first pocket instruction booklet back in the early 1930’s. Since then over 2 million copies of his instruction booklets have been published. Now, with the advent of the VCR, Jack has personally produced a one-hour VHS video tape. He describes it as his “full dress” bending demonstration and calls it “The Benfield Bending Technique.” This revised “Benfield Conduit Bending Manual” and VHS video tape are perfect companions for teaching proper bending techniques. Apprentice electricians watch the video then they use the manual as a textbook to “zero-in” on any bothersome bending problem.
4
About the Author
Electrical superintendents, training directors and journeymen electricians, by the thousands, have endorsed Jack’s simple, non-technical method for making conduit bends that fit. “After 60 years,” Jack says, “I still love to watch a good conduit man do his stuff. It’s great to see them make bends that drop into place and fit like a glove. I’ve noticed that even old-time electrical journeymen get a quiet thrill when a tough-to-make bend fits as though it had been molded in place."
Preface to the First Edition
5
Preface to the First Edition As I write these instructions my constant concern can be expressed in these three words ... KEEP IT SIMPLE! Readers will be happy to discover there is not a technical word in this manual. The Benfield method simply uses addition, subtraction and multiplication. Basic elementary arithmetic does it! Some conduit bending instruction books resort to trigonometry. Such high math over-complicates the simple business of making conduit bends that fit. I avoid such needless terms as sines-cosines-secants-cosecants-tangents developed lengths, etc. About all the electrician needs to know is where the end of his conduit stub-up will be, how far to space his bends apart to make true offsets and saddles, and where the back of his bends will lay. To be certain that these instructions are crystal clear I have used plain language with simple formulas, tables and diagrams. The Benfield technique works with ANY make of bender that may be found on ANY job. It works with hand-hickeys, electrically powered hydraulic tools and/or mechanically powered benders. These formulas work even if bends are made in the crotch of a tree or a hole in a wood block. A big thank you from the author goes to the many electricians who helped him along the way. Their valuable suggestions, their know-how, their on-the-job hints and bending tips have become the very substance of this manual. Those electricians have made a valuable contribution to the art of making conduit bends that fit! Jack Benfield, Author
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Preface to the Second Edition
Preface to the Second Edition New chapters...new clarity...new material. Chapters in this second edition have been clarified and rearranged...the “how-to-do-it” chapters are now in sequence and first in the manual (Chapters 1 through 11). Two new chapters have been added: Chapter 12: Bending PVC Conduit and Chapter 13: Mechanically Powered Ratchet Benders and Hydraulic or Electrically Powered Benders. A new multiplier is revealed for closer coupled “3-bend” saddles using a 60° center bend (see Chapter 5). Three new sketches illustrate conduit runs “over-the-top” (see Chapter 8). The wordage throughout this second edition is crisp, clear, and concise. Jack Benfield, Author
Introduction
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Introduction Conduit Bends Save Money! One reason benders are so popular and are so widely used is economy. Obviously, conduit fittings, 45° or 90° factory elbows, boxes, etc. can be used to accomplish most any conduit wiring job...but bending conduit on the spot is faster, more economical and makes a better looking installation. Bending saves cutting, saves the cost of elbows and couplings and it saves time. At current prices, it would take only twelve I1J4” EMT bends (made on location) to save enough on material to pay for the cost of a 1W’ foot pedal (two position) type bending tool. In addition, using bends in the run makes for a more streamlined job with less chance for a poor ground path. Some bending instruction manuals contain formulas and diagrams so steeped in high math that a mathematics professor might well suffer a brain convulsion. Because of this “overkill,” a mysterious aura of fear has clouded the very simple business of bending a piece of conduit. Making bends that fit right the first time is easy if one follows a few simple rules. Believing that simplicity is paramount, the author has used only basic arithmetic in revealing the bending “know-how” he has accumulated from a lifetime of personal contact with electricians all over the free world. There isn’t a technical word in this book. In plain language, it explains how to make bends that fit. The Benfield technique works no matter what brand of bender is found on the job.
Bending 90° Stub Lengths 9
Chapter 1
Bending 90° Stub Lengths It's a pleasure to watch a journeyman electrician who really knows how to bend conduit. A few quick measurements, a mark here and there plus a little muscle power transforms ten foot lengths of conduit into a series of sweeps, offsets, saddles, and 90° bends that look like they were molded in place. Making professional precision conduit bends is not difficult. Simply follow the easy-to-use rules set forth in this manual. Here are some tips on bending right angle stub lengths...such bends are called "stub ups" by the trade.
Making 90° Stubs There are three basic methods for making 90° stub-up bends. Methods 1 and 2 will produce pin-point precision accuracy; method 3 is good enough when speed is paramount-such as when concrete is being poured at your heels on a concrete slab job. Method 1: Marking the Conduit From the desired stub-up height, subtract the appropriate "take-up" for the bender (Table A) and place a mark on the conduit at that distance from the end. The tool "take-up" for stubs is constant on fixed radius benders. A symbol or benchmark (such as an arrow) is usually cast into the bender as shown in the accompanying illustrations.
Table A
Example: It will be noted in Fig. 1, that a 3/4" bender has a 6" take-up. To make a 9" high stub-up using either 3/4" EMT or 1/2" rigid conduit, subtract 6" from 9" and mark the conduit 3" from the end. Position the bender so the arrow is opposite the 3" mark and make a 90° bend. (6" + 3" = 9"). Note: If the bender does not have an arrow, use the mouth of the bender groove as your starting point and make a test bend. Check the result for tool take-up and score your own FIG. 1 METHOD 1: Marking the conduit.
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Chapter 1
mark on the tool at the appropriate point. (Avoid fractions...marks should be on the even-inch). Method 1 is most commonly used but it is slower than the other two methods because of the time it takes to mark the conduit. Method 2: Alignment with Folding Rule Lay a folding rule (or tape measure) on the floor parallel with the conduit as depicted in Fig. 2. The folding rule becomes your guide for correct positioning of the bender on the conduit FIG. 2 METHOD 2: Alignment with folding rule. so as to make whatever stub length you desire. Example One: To make a 9" stub in 3/4" EMT, allow 6" for the take-up in the tool. Position the rule so that the 6" digit of the rule is opposite the end of the conduit. Now locate the bender on the conduit so that its arrow is opposite the 9" digit on the rule and bend. Result: a perfect 9" stub-up. Example Two: Suppose 1/2" EMT is being bent with a 1/2" bender that has a 5" take-up. For a 9" stub, the 5" digit of the ruler should lay opposite the end of the EMT, and the arrow on the bender should lay opposite the 9" digit on the rule. Result: a perfect 9" FIG. 3 METHOD 3: Thumbnail and eyeball method. stub-up. Example Three: Suppose you want a 20" stub-up in 3/4" EMT. The 6" digit on the rule should be opposite the end of the EMT, the arrow on the bender should be opposite the 20"digit on the rule.
This method is fast and precise, and marking the conduit is eliminated...a good eye for alignment does the trick because wherever the arrow on the bender lays in relation to the folding rule determines the height of the stub-up. Method 3: Thumbnail and Eyeball Method This is called the "thumbnail and eyeball" method-no ruler!...no marking! Simply place your thumbnail on the conduit at the stub height distance you desire as illustrated in Fig. 3. Then position the conduit in the tool so that an imaginary plumb line from the outside heel of the bender groove is in alignment with your thumbnail, and bend.
For best results, bend on the floor. Your accuracy will be as good as your ability to "eye-ball" that imaginary plumb line. This method is usually accurate to plus or minus 1/4 inch...use Method 3 when speed is paramount.
Bending 90° Stub Lengths 11
Questions
& Answers
90° bends in small sizes of conduit (1/2" EMT, 3/4" EMT, 1/2" rigid or IMC) be made on the Q Should floor or with tool in the air? A All 90° bends should be made on the floor whenever possible.
bend has already been made in a length of conduit the pipe may not lay firm and flat for a Q Ifgoodanother floor bend ... what then? the second bend on a slightly raised platform (a 4" x 4" will usually do) or bend at the edge of a A Make loading dock, stairwell, etc. This allows firm, solid footing because the first bend hangs in free air and the portion to be bent lays flat on the floor.
Q Is bending on carpeted floors or soft sand good practice? Definitely not! Work on hard surfaces wherever possible. Bends can be made on a soft surface but accuA racy suffers and ripples or flattening may occur. Q Is foot pressure really important? Yes ... the more foot pressure the better the bend. Pinning the conduit tight to the floor throughout the A full arc assures uniform, pin point accuracy. Q What stance is best for bending on floor? A wide stance (feet 28" to 30" apart) is best. The author is right handed but he bends using heavy presA sure with his left foot. Use a stance most comfortable for you ... one foot on the bender, the other foot firmly on the conduit. One hand on the handle, the other hand free for body balance ... keep constant stiff-leg foot pressure (knee joint stiff) throughout the full bending arc.
Q What length handle is best? 38 inches is best for 1/2" and 3/4" size benders, 44 inch for 1" EMT benders and 54 inch for 1 ½ EMT A benders. Note: Avoid longer handles than these. Longer handles are cumbersome to work with and they invite too much pull on the handle. Remember, foot pressure is of paramount importance and avoid pulling the handle too much.
12
Chapter 1
Q What is the best method for marking conduits? Use a soft lead pencil; it is good practice to girdle the conduit the full 360° with your marks. A partial A mark may disappear from view because it is covered by the bending groove. A soft lead pencil or a narrow marking pencil is best. Too wide a mark may lose pin-point accuracy.
Q What is best position or stance when bending over the tool, i.e., with tool in air? Keep arm pressure close to the tool (conduit under armpit helps). Allow the tool assembly to rock forA ward as you complete the bend.
All About Offsets 13
Chapter 2
All about Offsets This chapter reveals a simple technique for making offsets in conduit or EMT with speed and precision. Speed is important on any job, but speed coupled with precision pays a triple dividend...saves time, saves waste, makes for a quality job. Conduit bends should fit right the first time. Bad bends double the cost, twice the labor, twice the conduit. By following these simple rules you will wipe out waste. The technique works for any fixed radius bender, hand type, mechanical ratchet type, hydraulic or electrically powered benders. As shown in Figure 4, an offset is two opposing angle bends made to clear an obstruction in the path of the run. Bends A and B must be equal in the degree of their angle. Obviously for precision results both bends must be made to the exact degree of angle chosen from Table B. Note: Careless approximation (a few degrees off, high or low) produces a poor, ill-fitting offset.
FIG. 4 Typical offset.
What is the best angle of bend to use for various offset depths? For shallow offset depths (3” or 4”), 30° bends are best. It’s easier to pull wire through gentle 30° bends and it is easier to calculate the needed distance between bends because the multiplier for 30° bends is simply TWO (offset depth x 2 = distance between bends). For offsets 5” deep or more 45° bends are best. The multiplier for 45° bends is 1.4 (offset depth x 1.4 = distance between bends). 45° bends for depths of 5” or more will look neater and trimmer. They take up less room because they are more closely coupled. For 2 inch depths, 22 ½ ° bends are best.
Table B
For little kicks into a pull box or a cabinet (1 inch depth or less), use 10° bends.
14
Chapter 2
Figuring distance between bends Figure 5 and 6 illustrate three different offset depths. Fig. 5 for 30° bends. Fig. 6 for 45° bends. Marks X and Y represent the distance between bends in all examples.
Knowing the depth of offset needed, and having established the angle of bend to use, and the distance between bends, you then need to know:
Where to start the first bend This is easy! The “shrink per inch” for offset depths is shown in Column 3 of Table B. If stringing pipe into (towards) an obstruction place the first mark Y beyond the edge of obstruction, the amount of shrink calculated from Table B. If offsetting away from an obstruction ignore the “shrink.” Figure 7 illustrates the distance between bends and the “shrink” for a 10 inch offset with 45° bends. In this case the shrink is 3%.
To save time, the calculations needed for offsets from 1” to 10” have been worked out and assembled in a Zip Guide for offsets (Table C). It indicates distances between bends for a range of offsets for 1” to 10” inclusive
FIG. 5
Distance between bends, 30° examples.
FIG. 6
Distance between bends, 45° examples.
All About Offsets 15
FIG. 7 Locating the first bend when making a 45° offset.
Table C
and also recommends the best angle of bend. Column 4 indicates the exact “shrink” to allow. Offsets greater than 10” must be calculated as described previously. The Zip Guide has proven to be so useful that manufacturers have applied them on the handles of benders. The Benfield technique works for all sizes of EMT, rigid conduit, or IMC. The same formulas can be used with power benders even on 6” conduit. It also works for any make of bender that may be found on any job. All offset bends should be started with the mark on FIG. 8 the conduit opposite the arrow on the tool. Obviously, it helps if the bender has a cast-in degree scale to guide the operator (See Fig. 8). Otherwise, some type of protractor or inclinometer should be held against the conduit to indicate the angle of bend. Summation: At any given angle the distance between bends determines the depth of any offset. Knowing the “shrink” tells the operator where to place a mark on the conduit to start the first bend.
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Chapter 2
Questions
& Answers
Q Should offset bends be made on the floor or with bender head in the air? in small conduits (1/2 inch EMT, 3/4 inch EMT and 1/2 inch rigid or IMC) may be bent in the A Offsets air. However, when making the second bend to complete the offset some journeymen prefer to bend on the floor.
Q How can I keep offset bends in alignment and prevent dog-legs? Before you fabricate the second bend be sure the first bend lines up in a perfect plane with (a) the rest of A the conduit, (b) the handle of the bender, and (c) the tool itself, as an extra precaution sight everything into alignment with a straight board on the floor, a joint in-the-flooring, the seam of a carpet, etc.
Q How do I make a double offset or as it is sometimes called, a 4 bend saddle? saddle is no more than two offsets back to back. Allow just enough straight conduit so as to A Aclear4 bend the obstruction before starting the second offset. (See Four-Bend Saddles, Chapter Five). Q Are your degree scale marks accurate for both EMT and rigid conduit? scale lines are engineered for EMT... i.e., 3/4” EMT should register on the line. If 1/2 inch rigid A Degree conduit is bent in the same groove bend 1° or 2° below the degree line. Q How can I best take out an over-bend in an offset? only a few degrees of over-bend exists use the conduit as a lever and give the back of the bend a A Ifsmart rap on a hard surface, such as a wood board or a hard floor. This will usually remove a few degrees of bend to bring it back into position.
Q Some benders have built-in spirit levels, aren’t they okay? levels are for 45° and 90° only and their use is further limited to floor bending. Levels cease to A Spirit function when the bender head is in mid-air. For a spirit level to indicate accurately even the floor itself must be level. False indications result if catwalk deck boards are used or if the floor is pitched for drainage, or if used on ramps, driveways, etc.
Q
Chapter Two says nothing about 60° x 60° offsets, yet your degree scale has a 60° slash mark...how come?
A
Try to avoid 60° angle bends for offsets. Wire pulling around them is difficult. If you are extremely cramped for space, 60° bends are OK, but 30° or 45° bends are always best if you have the room.
All About Offsets 17
Jack's "Timely Tips" BENDING WITH TOOL IN AIR: Keep hand pressure close. Tuck the conduit under the armpit. This position assures close-to-the-groove hand and body pressure. As the bend progresses allow your body and the entire assembly to rock forward. AVOID CROOKED OFFSETS: A “dog leg” occurs when the two bends of an offset are not in the same plane. To avoid this, bend the second half of the offset just a tiny bit (8° to 10° or even less...then sight down the pipe...if the bends are out of line, twist the conduit into correct alignment. Now as you complete the offset the “dog-leg” will disappear.
Make it your custom to use 30° bends for most offsets. Wires pull easier! A straight up handle {vertical to floor} indicates that a 30° bend has been made...and to establish the distance between bends the 30° multiplier is simply “two”...no fractions to multiply}.
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Chapter 3
Chapter 3
Back-to-Back Bends This chapter explains where to mark the conduit and where to position the bender for perfect backto-back bends. Although “back-to-back” is a term accepted by the electrical trade, it is really a misnomer. Actually, it means the distance from a fixed point on the conduit to the back of a 90° bend. Figure 9 shows examples, all of which call for accuracy to the back of the bend. Determining the distance from a point on the conduit to the back of a ninety (the distance between A and B in Fig. 9) probably is required more than any other bend on the job. For example, stubbing-up conduits so that the back of the bend centers properly with a chalked-off line on the deck form for a future wall partition is encountered on virtually every concrete deck job. FIG. 9 Five situations where the distance of the back of a 90° bend must be accurate. This is illustrated below. Some benders have built-in symbols on both sides of the bending groove as an aid to making perfect back-to-back bends. It may be a line, a notch, a letter, or some other symbol. For purposes of clarity in this manual a “star-point” symbol is used. Figure 10 shows a tool using a “star-point” symbol. With the bender positioned in any given spot, the starpoint predicts where the back of the ninety degree bend will lay.
Thus, if the back of the ninety is to end up 50 inches from a fixed point on the conduit, the 50 in. are measured off and marked, the star-point is then aligned with the 50 in. mark and the bend is made. On surface conduit runs, the backs of two nineties frequently must be made to fit snugly against both a ceiling and a wall, as in Fig. 11. Here again, if the star-point is used for both bends, they will fit perfectly against both wall and ceiling as though they were molded in place.
Back-to-Back Bends 19
FIG. 10 Star-point symbol on tool registers with mark on conduit. Completed 90° bend "centers" in future wall partition.
FIG. 12 If back-to-back bends are close together, make the second bend as you would a stub. However, a different approach may be required if the back-to-back bends are too close together. In Fig. 12, the two bends are so close together that the operator has too little conduit to work with if he attempted to bend back toward the first bend. In cases like this, the bender should be reversed and the bend made away from the first bend as shown in Fig. 12. Instead of using the star-point symbol, use the arrow at the mouth of the bender and allow for the appropriate take-up as though making a simple 24” long stub-up bend.
FIG. 11 Distance to back of bends must be ac- curate to make conduit lie snugly against ceiling and wall.
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Chapter 3
Questions
& Answers
Q Must I always mark the conduit prior to aligning the star-point for a back-to-back ninety? To speed the work, but the conduit end against a wall or fixed object...place a chalk mark on the A No. floor where you want the back of the bend to lay, align the star-point with that mark, and bend. A brick, a carton, a stick would serve the same purpose. Simply align the star-point with the edge of the object and bend.
Q Suppose I want the back of a 45° bend to lay snugly against an angle surface or truss...what then? still use the star-point. The star-point foretells where the back of the bend will lay regardless of the A You angle, i.e., it works from 0° to 90° or any angle in between. Q Should I use the star-point when bending with the bender head in the air (end of handle on floor)? Yes. It works in any position. When bending conduit over the bending shoe remember to keep constant A bending pressure close to the groove. Q If there is no back bend symbol on the bender how can I establish my own mark? easy. Make a test bend after first marking a line on the floor and a mark on the conduit. Before A That’s bending bring the two marks into registry...after completing the ninety measure the distance from the mark on the floor to the back of the bend. The result is the “shrink” distance. Now measure the “shrink” distance back from the mouth of the bender groove and cut a permanent reference mark into both sides of the tool with the edge of a file.
Jack's "Timely Tips" • GAUGING THE BACK OF A BEND WHEN IT IS LESS THAN NINETY DEGREES. Keep in mind that the star-point on the tool is a STATIONARY PIVOT POINT. Therefore, it indicates where the back of the bend will lay whether the angle is one degree or ninety degrees or any angle in between. • IF THE BACK OF THE BEND LAYS UP AN INCH OR TWO LONG, take another bite and over bend it to 120° or 130°. Then push the bend back to 90°. This will increase the radius but the back of the bend will drop an inch or two and lay up snugly.
• On the contrary, if the back of the bend ends up SHORT straighten the conduit and re-bend it to a shorter radius USING A HICKEY. Note: This applies only to 1/2” EMT.
Utilizing the "Gain"
21
Chapter 4
Utilizing the "Gain" Knowing the “Gain” enables the electrician to precut, ream and pre-thread both ends of a conduit before bending it. This speeds the work because he can prepare and thread both ends while the pipe is still straight. The “Gain” is the distance saved by the arc of a 90° bend as illustrated in Fig. 13. It is obvious that a path that short-cuts is shorter than one that doesn’t. Cutting thru a gas station takes fewer steps than walking around the comer. Therefore, it is easy to see why the overall length of a piece of conduit having a 90° bend is less than the sum of the horizontal and vertical distances when measured square to the comer. In Fig. 13, the dotted line distance X plus Y will be greater than the length of the conduit because of the “shortcut” taken by the bend. The difference between the distance X plus Y and the length of the conduit is called the “GAIN.” Knowing the gain therefore enables the electrician to cut, ream and thread both ends of a piece of rigid or IMC conduit while it is still straight. He then makes his 90° bend and both of the threaded ends will drop into position with perfect precision. How much will the gain be? It depends on two things--(a) the size of the conduit and (b) the radius of the bend. The larger the radius, the greater the gain. Table D shows the “Gain” resulting from a 90° bend in standard sizes of rigid or IMC conduit. The bending radii shown are the minimum values permitted by the National Electrical Code (Table 346-10).
This simple example shows how knowing the gain can speed the work. In Fig. 13, distance X = 30 inches and Y FIG. 13 Illustration of "Gain." = 15 inches. From Table D, 1” conduit has a gain of 4 inches. Therefore, the conduit in Fig. 13 should be cut 4 inches shorter than the sum of X and Y: 30 + 15 = 45 inches 45 -4 = 41 inches Thus, a piece of 1” conduit 41 inches long is needed to make the run shown Table D in Fig. 13.
22
Chapter 4
Questions
& Answers
“gain” for 90° bends is clear to me but suppose there is also a 4 inch deep offset (using 30° bends) Q The in the “X” portion of Fig. 13...what then?
A Offsets use up -extra conduit. See offset Table B, Chapter Two. The table tells you that 30° bends
shrink 1/4 inch per inch of offset depth. 4 x 1/4 inch = 1 inch
Therefore, you add 1 inch back-in and precut the conduit to a length of 42 inches instead of 41 inches.
Q Is the “gain” for EMT the same as for rigid conduit? providing the radius is the same for both. However, knowing the gain is not so important on EMT A Yes, because the threading operation is not involved. Obviously it’s awkward to cut threads close to a bend in rigid or IMC conduit.
Q How do I establish the “gain” for 90° bends of a longer or shorter radius than NE Code standard? make a test bend using the radius you intend to work with. Add distance X to Y ( Fig. 13) and A Simply then measure the actual length of conduit after it is bent. The difference is the “gain.”
Three and Four Saddle Bends
23
Chapter 5
Three and Four Saddle Bends An electrician, who can make fast “3-bend” and “4-bend” saddles, without reworking them to fit, is recognized in the trade as a tip-top conduit man. That’s why the saddle bend is selected to verify the truth of any journeyman’s claim that he is an accomplished conduit man. When a straight run of conduit has to be offset to cross over an obstruction such as a small water pipe or another conduit -a saddle bend is required. For saddles of moderate depth a “three-bend” saddle is recommended but if the saddle is more than 6 in. deep, a “fourbend” saddle is best because it occupies less space, follows the contour better, looks neater and uses less conduit. The Benfield technique for making fast, precision saddles removes the saddle bend mystery. The formula is so easy to follow that the saddle bend is at last, one of the simplest of all bends to make. The Benfield Saddle Formula and examples of three typical saddles are shown on the next page. Nothing makes an electrical contractor beam with pride over his crew’s craftsmanship than to see a lineup of parallel saddles, all looking as alike as peas in a pod. Now, by following the Benfield technique, saddle bends can be made time after time with amazing speed and precision. The procedure described in this chapter works for any fixed radius bending tool. It works for hand benders, mechanical or hydraulic powered benders and for all conduit sizes whether it be rigid steel conduit, IMC, rigid aluminum conduit, EMT or PVC. The critical dimensions that make up a threebend saddle are shown in Fig. 14. It is important to make the 45° center bend "A" first. Then make the two 22 ½° side bends at “B” and at “C.”
24
Chapter 5
Three-Bend Saddles Procedure. Measure the diameter of the object to be crossed over (depth “0”) and multiply that depth by 2 1/2. This will give you the distance “L” between mark “A” and “B” and between mark “A” and “C.” Keep in mind that the multiplier 2 1/2 is constant.
Irrespective of conduit size or type the depth of a “3-bend” saddle times the constant multiplier 2 1/2 determines the needed distance between bends. (See Fig. 14). Locating the 45°Center Bend (Mark “A”). Obviously, the conduit “detours” from a straight line in crossing over an obstruction. Therefore, to adjust for this, mark “A” should be placed at a point more than the distance you actually require as distance “X” in Fig. 14.
The distance you place mark “A” ahead depends on the depth “D.” In simple terms follow this rule: ADD 3/16 IN. FOR EVERY INCH OF SADDLE DEPTH.
FIG. 14 Three-bend saddle.
Making 45° Center Bend. As a convenience for electricians we have calculated in Table E the required distance “L” between bends for a range of saddle depths from 1 in. to 6 in. Table E also shows the amount to be added to distance “X” to locate starting point “A."
Table E
Measure distance “L” on conduit both ways from mark “A” and mark the conduit at “B” and at “C.” Align mark “A” with the two notches in the groove of the bending tool or the tear-drop symbol and make the 45° center bend (see Figs. 15 and 16). Locating the 22 1/2° Side Bends. Align mark “B” with the arrow on the bending tool (see Fig. 17) and make a 22 ½° bend.
Repeat this by making a 22 1/2° bend at mark “e” also at the arrow.
FIG. 15 Benchmarks on tool assure bending precision.
The three-bend saddle is now complete and should appear as shown in Fig. 14.
Three and Four Saddle Bends
Note: Some electricians prefer a closer coupled saddle using a 60° center bend instead of 45°.
In that case, the two side bends “B” and “e” should each be at 30° instead of 22 1/2° and the multiplier is 2 instead of 2 1/2 (see Fig. 14); i.e. diameter of object to be crossed (D) x 2 = distance between bends.
Four-Bend Saddles
FIG. 16 Conduit aligned for 45° and "A."
A four-bend saddle is the same as two offsets in tandem (see Fig. 18). It is simple to make these double offset saddles; follow the offset instructions outlined in Chapter Two, allowing just enough straight conduit between the two offsets to clear the obstruction. Comment: Electrical journeymen in North America may be interested to know that in England and the U.K. they refer to our saddle bend as a “cross-over bend” or a “bubble-set.” (A “saddle” to the British electrician is a 2-hole pipe strap). FIG. 17 Conduit aligned for 22 1/2° bend.
FIG. 18 Four-bend saddle.
25
26
Chapter 5
Questions Q
& Answers
Your saddle technique works okay when the saddle comes near the middle of a 10ft. length of conduit but suppose it comes close to one end?
A
Let us say you have only 12 in. of straight conduit left to use as a lever in making the second 22° bend at “C” (Fig. 17). Slip a pipe sleeve over the short end for use as extended leverage. Bend over the bender groove (tool in the air). The sleeve assures c1ose-to-the-groove pressure and provides the needed leverage to complete the 22 ½° bend.
E in Chapter Five indicates that a 4 in. deep saddle will cause the center mark “A” to shift 3/4 in. Q Table (3/16 per inch of depth). What then is the overall shortening end to end?
foot length of conduit after making a 4 in. deep 3-bend saddle will measure only 9 ft., 10 1/2 in. A AThetenoverall shrink is figured at 3/8 in. per inch of saddle depth...4 x 3/8 = 12/8 or 1 1/2 in., i.e., just double the values shown in Table E, Col. 3.
Q I have trouble making saddles without dog-legs. How do I prevent this? you actually make bend “B” and “C” ( Fig.17) you adjust the conduit in the groove (after comA Before pleting bend “A”) until everything lays in one plane. By “everything” we mean the conduit...the bender groove...and the bender handle too. As a further precaution align “everything” up with a straight mark of some kind on the floor. It could be the edge of a board...the seam of a carpet…the metal divider in a terrazzo floor...floor tiles, etc.
Q How do I allow for shortening of the conduit on the 4-bend saddle illustrated in Fig. 18? Allow the same as you would for two 5” deep offsets (See Table C, Chapter Two). Col. 4 indicates a 5 A in. offset with 45° bends shortens the conduit 1 7/8 in. In Fig. 18 we have two 5” deep offsets...therefore, your 4-bend saddle would shorten the conduit 2 x 1 7/8 in. or 33/4 in. in overall length.
Three and Four Saddle Bends
27
Jack's "Timely Tips" THREE-BEND SADDLES: Don’t attempt a 3-bend saddle if the object measures more than 6” in diameter. Larger diameters call for 4-bend saddles.
For tighter, closely coupled 3-bend saddles try a 60° center bend and two 30° side bends...and change the constant multiplier to 2 instead of 2 1/2. Not all pipe saddles need be made with the tool in air (handle end on floor). But, if bending on the floor you must make the side bends near the end of an elevated platform or at the edge of a loading dock or a stairwell. This allows previously made bends to lay in free air thus providing firm solid footing because the portion to be bent lays flat on the floor.
28
Chapter 6
Chapter 6
Bending with Hickeys Variable Radius Bends History If you ask an old-time electrical journeyman to hand-bend rigid conduit, he’ll reach for a hickey, not a bender. A hickey can be defined as a rugged, compact, chunky casting of steel or iron with an integral side opening hook large enough to receive the size conduit it is designed to bend. The origin of the name “hickey” dates back to about 1910, the days of gas pipe. In those early times gas pipe was sometimes used as electrical conduit. The need for bending it was obvious, but tools were not yet on the market. Electricians, therefore had to improvise bending tools by, for example, taking a one inch IPS plumber’s "T" fitting , sawing out the side of it, bell-mouthing all sharp edges, then screwing a piece of 1 -in. steel pipe into the top hub to serve as a handle. That’s how hickeys were born. The men just called them “hickeys,” and the name stuck. Even today one definition given in the dictionary for the word “hickey” is “any device or gadget whose name is not known or is momentarily forgotten.”
Uses Hickeys are essential on every job for very-short-radius bends such as are required to fit into shallow slabs and narrow partitions in modern construction. Short radii are often needed for conduit wiring of machinery, printing presses, oven equipment and the like. Hickeys are also used to shift, or “jockey,” already installed conduit runs a few degrees to get conduits into proper position. A good hickey, therefore, should grab on and hold firmly when reversed...some do, some don’t. Originally, hickeys were used only for heavy-wall, rigid steel conduit. Now they are made for EMT, aluminum conduit, and IMC conduit. Three manufacturers now market a combo hickey. Each tool makes good bends whether used for rigid conduit, EMT or IMC. The realistic size range for hand bending with hickeys is from 1/2-in. through 1 1/4-in. EMT and from 1/2-in. thru 1-in. rigid or IMC conduit.
Bending with Hickeys Variable Radius Bends
29
Fig. 21 illustrates the stubber type hickey made to bend all three conduits...EMT, rigid (steel or aluminum) and IMC. Good hickeys grab on and hold in any direction. Foot control is paramount on hickeys to assure that bending segments are evenly spaced and uniform.
It’s safe to say that the good old conduit hickey is with us to stay. The versatility of hickeys for making the unusual bend has earned them a well deserved place in every electrical contractor’s tool inventory.
Using a Hickey
FIG. 21 Features of a hickey.
A hickey hooks on the conduit like a fist and is manipulated like a pry-bar when fitted with a steel pipe handle as a lever. A hickey is inched along or shifted on the work during the course of the bend. Uniform, evenly spaced bites are recommended. The closer the bites, the shorter the radius. Usually, 10° or 15° of bend at each bite produces a NE Code radius bend. A shorter than NE Code radius can be made when it’s necessary. A “bender,” on the other hand, makes only one arc-one fixed NE Code radius. The contour of a hickey bend is controlled by the operator. A good hickey man masters his technique only after the benefit of practice, patience, and experience. One marked advantage of the hickey is its versatility. It will produce short, medium, long, or extra-long radius bends. It is also ideal for concentric runs where each bend is of slightly larger radius than its neighbor. We will deal with concentric bending technique later in this chapter. Guess work or “eye balling” the degree of bend is not advised. If the hickey has no degree of angle indicator it is recommended that the operator gage the first 10° bend using a protractor. In so doing he should fix in his mind the length of stroke it took to make the first 10° arc and keep repeating that same stroke on subsequent bites.
Concentric Bends Making good bends on individual lengths of conduit can be mastered with a little practice. But what separates the novice from the craftsman is the concentric bending of a bank of conduit, each with its own radius of bend, so the completed installation looks good. Using the Benfield method shown in Fig. 22 is a sure-fire way of doing the job right. Prior to bending, place reference marks on the conduits (as shown on the chart). Bend in nine equal 10° segments, i.e. nine 10° bites = 90°. Start all bends at arrow on tool. Hint: Hickey bends should be made on the floor with firm foot pressure on or against the tool.
30
Chapter 6
Example: For concentric hickey bends in 1/2” EMT or Rigid. 1st run:
(90° bend) -nine 10° segments spaced 3/8” apart. 2nd run:
(90° bend) -nine 10° segments spaced 3/4” apart. 3rd run:
(90° bend) -nine 10° segments spaced 1” apart. 4th run:
FIG. 22 Guide for concentric bends.
(90° bend) -nine 10° segments spaced 11/4” apart. Etc., etc., etc.
Making Stub-ups
Table F
Chapter 1 shows how stub-ups are made using a bender. Exactly the same techniques can be employed while using a hickey, except Table F must be used for the take-up.
Bending with Hickeys Variable Radius Bends
Questions
31
& Answers
Q Can hickeys be used to shift conduit stubs on concrete slab work in the case of a missed partition? Usually it is best to remove the handle, placing the hickey head only on the conduit. The hickey handle A Yes. is then sleeved over the conduit close to the hickey head and used as a lever to bend the “wandering stub” back into proper position. The hickey head is rested at the concrete floor level. Care should be taken to keep the “hook end of the hickey” towards the operator less after bending the hickey is locked tight to the floor by the bend.
Q Can accuracy be maintained with hickeys or is it all guesswork? a test 90° bend...count the number of bites taken, and then measure the take-up. Use this take-up on A Make subsequent bends and your accuracy will usually be within 1/4-in. plus or minus. Q Can a 90° hickey bend be altered up or down? Yes, by reworking the bent portion into closer segments. This works providing the hickey grabs on without A slipping. Reworking is limited to 1/2-in. rigid conduit but do not attempt to rework EMT with a hickey -it kinks!
Jack's "Timely Tips" • SUPER-SHORT RADII WITH HICKEYS: On 1/2” or 3/4” EMT insert a fairly snug fitting steel screen door spring within the EMT area to be bent. Make a hickey bend in several short bites...be rough...don’t baby it... but bend BEYOND a 90° bend. When you push it back to 90° the pressure is released and the spring can be easily removed. Note: A piece of armored cable...a jumbo portable electric cord, a rope or rubber hose will work as well if a suitable spring is not handy. But such inserts should fit snugly to provide internal support and be lubricated so they will slide out easily. • Don’t underestimate the importance of the uniform spacing between bites as the hickey is “inched along” during the bending operation...non-uniform spacing develops into a “sled runner” as defined on page 84.
32
Chapter 7
Chapter 7
Rolling Offsets (Around Corners) and 90 Compound Belts °
Often it makes a better looking installation and it is more economical to use conduit bends to turn a 90° corner. This applies whether it be an outside corner or an inside corner. This chapter explains how to do both. Let us suppose the job calls for an exposed run of conduit from a sign, a light, or a piece of equipment on the East wall of a building to a control switch to be mounted at a convenient level on the South wall of the building. Such a run would look better and cost less if the outside corner turn is made with a “rolling offset.” The Benfield technique for making regular offsets to exact measurement is explained in Chapter Two. For your convenience the Benfield Offset Formula and Zip-Guide Speed Table in condensed form is reprinted at the end of this chapter. (See Table G). To turn the corner without the use of fittings, simply bend a pair of offsets in tandem as shown in Figures 23, 24 or 25. For “rolling offsets” it is best to use 30° bends for easier wire pulling. Here’s how it’s done:
Table G
Rolling Offsets (Around Corners) and 90° Compound Belts
33
External corner Step One: Bend offset “A.” This offset must be made just deep enough to allow the conduit to clear the corner. (See dimension “X,” Figure 23). Note that offset “A” on East wall is made first. Step Two: Allow a minimum of 4” of straight conduit before starting offset “B." Step Three: With bender in air, (end of handle on floor) position the conduit in the tool so the completed offset “A” rests towards the right and in a plane at 90° to the bender groove. Step Four: Make offset “B.” Note: In Figure 23 the run is from right to left.
If the run was left to right (West wall to South wall-Figure 24) FIG. 23 Rolling offset external corner position conduit in the tool so completed offset “A” rests towards right to left. the left and in a plane at 90° to the bender groove before starting offset “B.” Step One: Bend offset “C.” This offset depth must be measured outside to outside. See dimension “Y.” Figure 25. Step Two: Allow a minimum of 4” of straight conduit before starting offset “O.” Step Three: With bender in air (end of handle on floor) position the conduit in the bender so the completed offset “C” rests towards the left in a plane at 90° to the bender groove. Step Four: Make offset “O."
FIG. 24 Rolling offset external corner left to right.
34
Chapter 7
Note One: In Figure 25, the run is from right to left. If the job requires a run from left to right position conduit in the tool so completed offset “C” rests towards the right in a plane at 90° to the bender groove before starting offset “O.” Note Two: If you happen to reverse a rolling offset by mistake it’s no problem...just save the bent section for use elsewhere. Here’s why: (a) An external rolling offset (right to left) as per Figure 23, works perfectly for an internal corner (left to right). (b) An external rolling offset (left to right) per Figure 24 works fine for an internal corner (right to left) as in Figure 25.
This technique works for any combination of angles (60°/ 30°, 22V2°/67V2°, 45°/45°, etc.). Let the folding rule (or tape measure) tell you the proper combination of angles to use for each compound 90° bend. Here’s how to do it. Step One:
As shown in Fig. 25A, use a tape measure or folding rule to simulate the compound bend to be made. Measure (with rule in place) the distance between point “A” (flush with wall) and point “B” (flush with the floor). Step Two:
Mark this distance on the conduit as point “A” and point “B.” This is the space needed between the two bends. Step Three:
Make the required angle bend at point “A.” Step Four:
Make the required angle bend at point “B."
FIG. 25 Rolling offset internal corner right to left.
IMPORTANT NOTE: Before bending, be sure points “An and “B” are in alignment with the Starpoint on the Benfield bender. The result will be a perfect fit as shown in Figure 25B.
FIG. 25A Measure distance between "A" and "B"
FIG. 25B In this example, two 45° angles and a 12-inch spacing between points "A' and "B" were used.
Rolling Offsets (Around Corners) and 90° Compound Belts
Questions
35
& Answers
Q Should “rolling offsets” always be used to go around comers? No. Rolling offsets are practical only when the direction of the conduit runs parallel to the corner to be A turned. Q Must the angle of bends for “rolling offsets” always be at 30°? No. In some cases 22 1/2° or 45° angle bends would work just as well. It’s a matter of journeyman’s A choice...wire pulling should be considered.
36
Chapter 8
Chapter 8
Keeping Conduit Run "On-the-Flat" at Ceiling Corners and "Over the Top" To obtain perfection, layout your conduit runs on exposed work so that all bends lay on the flat. You will really be proud of your work and quickly agree that the extra pains you took were worth it. Bends can be employed to turn outside or inside comers anywhere and they have the mark of professionalism
Over the top You can use conduit bends to go “over-the-top” of a wall, in sign work, roof-top lighting, etc. ( Fig. 26). The result is better than when a “gooseneck” is used. A gooseneck bend ( Fig. 27) is not good practice because the open loop appears as a sturdy hand-grab, but it is usually unsafe.
Wall to ceiling Making a transition run from a wall to a ceiling can be tricky. Conduits if run directly from a wall switch to a center ceiling fixture using a gooseneck bend will leave an ugly air gap at the ceiling corner. To avoid this air space, use two 90° bends as shown in Fig. 28. One bend lays flat on the wall...the other bend lays flat on the ceiling.
FIG. 26 Over-the-top with two 90° bends (wall to roof).
To do the job right takes only an extra foot or two of conduit plus a few seconds to make the extra 90° bend. The improvement is obvious. It’s the mark of good craftsmanship to keep such exposed conduit runs on the flat.
FIG. 27 Over-the-top with gooseneck is BAD PRACTICE.
FIG. 28 Avoid air gap at ceiling. Use two 90° bends.
Electrical Conduit in Concrete Slabs, Shifting EMT Stubs, Etc.
37
Chapter 9
Electrical Conduit in Concrete Slabs, Shifting EMT Stubs, Etc. Over the years electrical contractors and journeymen electricians have given the author many tips that have become valuable aids on the job. These ideas are passed along with the hope that they will be helpful to others installing conduit, IMC and EMT in the concrete pour. The five sketches -Figs. 29, 30, 31, 32, and 33 in this chapter were made on an actual installation. They represent typical problems encountered in modern concrete deck construction.
Cradle your deck runs It requires only a few extra inches of conduit, IMC, or EMT to “cradle” the conduit runs on the deck...and the benefits are manifold: If wire-tied securely to the steel, the cradled conduit runs are “locked” securely in two directions.
FIG. 29 Proper cradling.
...stub-ups should be tied together above the level of the pour …such runs are turn-proof, won’t twist, shift or get knocked about even if the run is brutally trampled upon by other trades during the pour.
Wire-tie deck level first ...Tie down the horizontal runs at the deck level first. ...Then wire-tie the stub-ups together above the FIG. 30 Sequencing is important. floor level.
38
Chapter 9
This sequence is important! It provides extra rigidity to the run and helps resist shifting of stubs due to manhandling, concrete buggies, tampers, careless laying of catwalk planks, etc.
Wire-tie groups of stubs together ...When stub-ups are in close proximity, tie them as illustrated in Fig. 31.
FIG. 31 Conduits in close proximity.
...Use a piece of scrap thin wall or conduit...here all five stubs are locked together structurally. Note: The bend in the foreground has been “cradled” for added stability.
Enter narrow partitions obliquely ...Had we attempted a straight entry in Fig. 32 half of the 90° bend would stick out of the pour.
FIG. 32 Oblique entry.
...Entering obliquely allows entry into unbelievably narrow partitions. Make a 45° or 60° bend at deck level just ahead of the partition. Then make a normal radius 90° bend stub-up where the switch leg is to be located.
...Oblique entry also allows the use of code radius bends throughout for ease in wire pulling. A tie or two ahead of the switch leg lends stability to the run and stub-ups stay secure. Using this “oblique entry” technique also means that narrow partitions and shallow slabs will no longer present a problem.
Shifting a stub after the concrete has set Here we explain the best method for shifting a stub that has missed a partition in concrete slab construction. ...Remove the bender handle. …Chip out enough concrete around the stub to allow the heel of the bender itself to drop below the surface so the groove will fit snugly around the conduit as shown. Note: Take care not to place the hook end of the bender downward or the bend will lock the bender to the concrete slab and the tool cannot be removed without mutilating the conduit.
Electrical Conduit in Concrete Slabs, Shifting EMT Stubs, Etc.
...Slide a pipe sleeve over the stub (as shown in Fig. 33) and use the sleeve as a lever to provide close-in bending pressure...the closer the better. This forces the conduit to bend in the groove until it is worked into the desired position. To do this corrective work some electricians rig up a “right-angle handle.” This is done by the use of a threaded IPS nipple long enough for threads to clear the collar of the bender. To this nipple they attach a plumber’s 90° short elbow and screw a conventional bender handle into the elbow. This assembly gives the operator a handy means of holding the bender head steady and firm as he forces the conduit (using the pipe sleeve) to bend in the bender groove until it FIG. 33 Shifting a stub. gets into the proper position.
39
40
Chapter 9
Questions
& Answers
How do I correct a 1/2-in. or 3/4-in. EMT stub that has been knocked over and kinked flat together at the concrete deck level?
Q A Don’t attempt to remove the kink with a hickey or bender. Instead, do this:
...Using an IPS sleeve over the EMT push the stub back into vertical position. (A good portion of the kink will disappear by this operation alone). ...Now use a bullet-nosed steel rod and ram it down inside the EMT, turning it to and fro as you go. This will usually bring the kinked portion back into round again.
Q
I find certain types of concrete cause conduits to corrode or rust right at the floor or ceiling level...how can I prevent this?
A
Before concrete is poured it is wise to daub all stubs, for 3 or 4 inches, at the deck level with a coating of red lead paint.
Q Stubs will get knocked over but can I do something to minimize this trouble? Yes...immediately after the forms are removed drop a piece of hollow tile over the stubs and leave the A tile there until the likelihood of mechanical injury has passed. This serves as a constant, but gentle warning to other trades to keep clear.
Jack's "Timely Tips" • MARKING THE CONDUIT FOR PRECISION BENDING: Some galvanized conduit finishes are greasy smooth...a lead pencil doesn’t mark clearly on such finishes. Use a soft tip marking pencil.
• Don’t make your marks on the conduit too wide. A pinpoint precision bend could miss by as much as the width of your mark. • HOW TO REMOVE A SHARP KINK IN 1/2” EMT. Straighten the EMT as shown in Fig. 34 (page 61). The kink will nearly disappear. Now, rebend it in the same area in any direction you choose, BUT you must now use extra heavy foot pressure to coin the kinked area back into round again.
Removing Bend in 1/2" EMT 41
Chapter 10
Removing Bend in 1/2" EMT It is entirely practical to remove even a full 90° bend from 1/2” EMT. Obviously, angle bends and offsets can likewise be removed by following the procedure indicated in Fig. 34. Do not attempt to straighten the EMT by reversing the bent portion in the groove of the bender. Forget the bender groove entirely and get rough by using the handle only as a combo lever and sleeve and push the EMT bend back down to the floor progressively as illustrated in the diagram. Work the EMT back into the handle as you FIG. 34 Removing a 90° bend at 1/2' thinwall. straighten the bent portion until the bent area disappears completely into the bender handle. After the major straightening is done any remaining ripples in the EMT can be removed in the groove of the bender {tool in air, handle end on floor}...just a touch here and there is enough to get the EMT straight enough to be bent again in any direction. Sharp kinks in 1/2” EMT can be removed in the same manner. Note: When rebending EMT in the same area it was straightened, take care to apply extra-heavy foot pressure. This extra foot pressure will “coin” the metal forcing it to conform to the bending groove. Done properly, only you will know that the EMT has been bent, straightened and rebent into proper position. This procedure is not practical in sizes larger than 1/2” EMT.
42
Chapter 11
Chapter 11
Bending Surface Metal Molding A relatively new one-sweep bending tool enables the electrical journeyman to bend surface metal molding just as he would rigid conduit or thin wall EMT. The tedious feeding of wires thru comer fittings, angle elbows, etc. with all the accompanying cutting and fitting is often unnecessary if bends are used. Metal molding can be installed and wires pulled in, just like with thin wall EMT. It’s a big plus to be able to pull wires thru the surface raceway, especially if offsets and multiple one-sweep 90° bends are involved. (This tool is shown in Figs. FIG. 35 Action view. 35 and 36). On flange type surface metal moldings the bender illustrated bends smooth sweeps “flange-in” or “flange-out,” but this tool will not bend this rectangular metal molding sideways. To make sideway turns, fittings must be used. The bender illustrated bends the popular sizes of molding and with the use of an adapter, that snaps into the bender groove, it bends the “baby size” molding as well. This metal molding bender has every built-in feature found in one-sweep rigid conduit and EMT benders illustrated in earlier chapters. Stubs, offsets, and 3-bend saddles can be fabricated by following the same technique described throughout this manual. Two separate degree scales are permanently cast into this tool... FIG. 36 Surface metal molding. one on each outer face of the tool...these degree calibrations are for different diameters of molding. The bender comes complete with a twopiece (space saver) handle as shown in Fig. 36. Pin-point precision bends can be made if the operator follows the manual supplied with each tool. Another aid is a scuff resistant Zip-Guide label affixed to the handle. This guide provides the operator with a convenient at-point-of use reference. This Lip-Guide is reproduced in FIG. 37 Zip-guide for surface metal molding. Fig. 37.
Bending Surface Metal Molding
43
How to make 3-bend saddles in surface metal molding FIG. 38 Making 3-bend saddles in surface metal molding.
Example: Crossing over a 2” diameter water pipe calls for a typical three-bend saddle. A 45° bend at the center of the pipe (point A) and 22 1/2° bends on each side (points B and C).
Note in Fig. 38 that center point “A” shifts as a result of the saddle bend. To allow for this shift the constant rule is: The raceway shortens 3/16” for every inch of saddle depth. Saddling a 2” diameter water pipe (point A) will shift 2 x 3/16” = 3/8”. Therefore, the center mark should be placed 3/8” ahead to allow for this shortening or shift.
FIG. 39 Location of marks. To locate points “B” and “e” use the table in Fig. 39. In this case a 2” diameter water pipe calls for a distance of 5” each way from center point “A.” Make the 45° center bend “A” first placing the mark opposite the rim notch on the groove of the bender.
FIG. 40 Proper position of bender.
Next make 22 1/2° bends at “B” and “e” placing these marks opposite the zero degree line on the tool. Fig. 40 illustrates the position of the bender. Remember this rule: For best results in making 3-bend saddles always make the center 45° bend first...Then make the two 22 1/2° side bends to complete the saddle.
90° changes in direction of surface metal molding are usually accomplished with fit- tings. However, offsets to get around obstruc- tions are not so easy to accomplish. Bends to follow curved contour must be made with a bender, using the same techniques as used in bending conduit.
44
Chapter 12
Chapter 12
Bending PVC Conduit The author’s bending experience has been primarily with metallic raceways, steel or aluminum. However, PVC conduits are now so widely used that a keen interest in bending it exists. The author hopes that his observations on this relatively new art will be helpful to PVC users. Standard hand benders can be used not to bend PVC conduit but to serve as a template to form it while hot. However, to be formed the PVC must first be uniformly heated to the temperature recommended by the manufacturer. Once the heated area is formed in the bender groove (and preferably securely clamped) it must be chilled immediately to negate the “memory” of PVC. Unless quickly chilled the bent area will back off or “un-bend.” This PVC “memory” will diminish in speed as it cools but a tiny reverse movement will continue for hours.
Heating methods A. Electric oven heaters (infrared or calrod elements)
Bending PVC conduit only requires the ap- plication of heat. A bender can be used as a template for establishing the proper bending radius for small sizes.
B. Electric blanket (element embedded in silicone rubber) C. Heat gun (hot air blower) D. Conventional hair dryer Note 1. When possible heat the area inside as well as outside the conduit. Note 2. In a pinch use the hot exhaust from the tail pipe of a pick-up truck. To obtain uniform all-over heat carefully rotate the PVC conduit in the motor’s hot exhaust.
Chilling methods 1. Immerse the bent area in a cold water bath. 2. Wrap the area with cold wet towels. 3. Hose down the bent portion, both inside and out, with cold water. Note: The water hose method is messy but it works.
Using Benfield Formulas and Symbols with "Chicago" Rachet-Type, Hydraulic or Electrically Powered Benders
45
Chapter 13:
Using Benfield Formulas and Symbols with "Chicago" RachetType, Hydraulic or Electrically Powered Benders Previous chapters in this manual deal primarily with fixed radius hand benders. However, every Benfield formula and technique works for any bender (big or small)...and because the “no-trig” Benfield method is based upon simple arithmetic the size of the conduit or the type of power bender used is immaterial. That may be welcome news to the electrician who first learned how to bend using 1/2” thin wall conduit. That electrician can now use those basic bending formulas on the big stuff too. The technique is the same for stubups, back-to-backs, offsets or saddles. The measurements change but the formulas don’t. Excellent instructions are furnished by the manufacturer of “Chicago” ratchet type mechanical benders… in fact, all hydraulic or electrical benders come with good manuals as an aid to precision bending.
To locate a star-point It’s no problem if the electrician feels more comfortable using the old standby Benfield “Star-point” symbol (see Chapter 3) for back-to-back bends. Any make of tool (hand or power type) can easily be modified to provide a back-of-bend indicator symbol. To locate the exact spot on the tool for such a “star-point” Example of "Chicago" ratchet-type bender. follow these simple steps: Step 1 Girdle a pencil mark on a test length of conduit. Step 2 Lay the test length of conduit on the floor abutting it firmly against something immovable such as a wall. Step 3 Draw a chalk line on the floor exactly opposite the pencil mark on the conduit. Step 4 Make a test 90° bend with the pencil mark on conduit even with the “jaw” (hook) of the ratchet bender. Step 5 Place the bent conduit back on the floor where it was at the start. Step 6 Measure the distance (inches) from the chalk line on the floor to the back of the 90° bend just made. Step 7 The result is the “shrink” for that sector (shoe).
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Chapter 13:
Step 8 Now measure this “shrink” distance back from the “jaw” (or hook) of the bending shoe and mark your tool by filing a visible “V” notch. The notch is your future “Star-point” for back-to-back bends. As with the Star-point, a stub-up symbol can be marked on any bending tool. Follow these simple steps:
To locate a stub-up symbol Step 1 Make a pencil mark on the conduit exactly even with the jaw (or hook) of any bender...make a test 90° bend. Step 2 Use a T-square to be certain the test bend is a true ninety (90°). Step 3 Measure the distance from the floor surface to the pencil mark on the conduit. Step 4 This distance is the “take-up” {inches} for that bending groove...make a note of it. Step 5 At some visible point, file a “notch-mark” on the sector. This distance is your “take-up” symbol for future 90° stubs. (To avoid fractions, this mark should be placed on the even inch).
Making offsets and saddles Most ratchet benders have a degree-of-angle indicator. If no degree scale, use a protractor to check angle of bends. Then follow the Benfield offset formula (Chapter Two) using those constant multipliers just as though you were working with standard hand benders.
Hand Bender Types Described 47
Chapter 14
Hand Bender Types Described Sub-Section "A" - Two position foot pedal benders The electrical journeyman is not expected to bend large conduit sizes by hand. It is generally recognized that 1 1/4 in. EMT and 1 in. rigid steel or IMC conduit are the limits. Mechanically powered, ratchet-type, gearpowered, or hydraulic benders are used for the larger sizes. To facilitate bending 1 V4 in. EMT and 1 in. rigid steel or IMC conduit, manufacturers have designed hand benders with two-position foot pedals. These benders make it possible for the electrician to apply his full body weight to the conduit with greatly increased leverage. Fig. 41 illustrates such a bender. Good results will be achieved if proper attention is paid to a few basic techniques. The simple steps shown in Fig. 42 illustrate the progressive positions of a Powr-Jack foot pedal bender in the course of a 90° bend. These positions are designated A, B, C and O.
FIG. 41 Foot-pedal bender. Position A
With the conduit inserted in the bending shoe and the foot pedal in the lower of its two positions, grasp the bender handle with one hand and place the ball of one foot on the extreme end of the pedal. Step up onto the pedal, stiffening the leg, and apply full body weight to the pedal through the ball of the foot. Do not bend the knee. The free arm and leg should be extended as required to maintain balance while the force is being applied. Coordinate “stiff leg” foot pressure with each pull on the handle. Push down and pull simultaneously in small amounts for best results. Do not attempt to pull hard on the bender handle; the major bending force should be applied by the foot. Too much pull on the handle with arm and shoulder lifts the entire assembly (bender and conduit) up off the floor, allowing the conduit or tubing to bend outside the groove. Without side wall support the conduit is sure to buckle, FIG. 42 Using foot-pedal bender showing kink, or bend to an uneven radius. positions A, B, C and D.
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Chapter 14
Position B
Repeat step A a number of times, applying force in small amounts until edge of pedal rests against conduit. At this point the conduit has been bent to a 55° angle. Position C
Lift the pedal with the toe of the shoe until it locks into the second (upper) position. Position D
At this point the operator should combine heavy (two arm) force on the handle along with heavy foot pressure on the step, and bend in small amounts until the 90° bend is complete. Note: When bend has progressed to “C” position some operators prefer to “about face” and bend from a position at 4 o’clock to the work. It may seem odd, but a right handed electrician often prefers to bend with left leg foot pressure...and vice versa.
Obviously, this tool is not intended for production bending where hundreds of bends per day are involved. Rather, it is a supplementary tool, well-suited for service-truck use where quick set-up and speed are important. It meets the need for a simple, low-cost, portable, light weight bending device and provides an economical solution to the problem of bending 1 1/4 in. EMT and 1 in. rigid steel or IMC conduit with precision accuracy.
Questions
& Answers
Q Would a longer handle make bending easier with the big Power-Jack model? No! Normally one would expect that longer leverage would make bending easier but in this case it is quite A the opposite...a longer handle would invite more pull on the handle than is needed. Too much handle pull causes the entire assembly to lift up off the floor and a kink results. Foot pressure is paramount! Constant, heavy, stiff leg foot pressure pins the conduit or EMT tight to the floor, assuring a smooth, accurate bend.
Q What are the recommended handle lengths for benders and hickeys? A For electricians of average height handles should be:
Hand Bender Types Described 49
Q Are precision results the same on Powr-Jacks as on standard models? A Yes. Same symbols, same degree scale, same accuracy. the big Powr-Jack be used in the air...that is with handle on floor and bending the conduit over the Q Can groove? recommended. For best results with Powr-Jacks make all bends on a hard surfaced floor. If a previous A Not bend prevents the conduit from laying firmly on the floor it is best to bend at the edge of a loading dock, platform or stairwell. This permits the previously bent portion to lay in free air and allows solid footing for a floor bend.
Powr-Jack foot pedal benders be bolted flat out on a bending table permitting their use as a stationary Q Can bench bender?
A
Yes. However, we recommend that a long pipe sleeve be telescoped over the EMT, or rigid conduit to serve as extra leverage and provide the dose-into-the-groove pressure needed for good results.
Q During the course of the bend does a vertical (to the floor) handle indicate a 30° bend in the work? Yes. All benders, hickeys and foot pedal benders shown in this manual are designed so that a vertical A handle indicates a 30° bend.
Jack's "Timely Tips" LONGER THAN CODE RADII: Foot pedal benders may be used to make longer radius bends in smaller size conduits; i.e., a big 1 1/4” bender with an 11” take-up can be used to bend 1/2” or 3/4” conduit, IMC or EMT. Care must be taken to FORCE such under sized conduits to lay tight to the bottom of the groove as the bend is fabricated. (Some flattening will be evident.) If a bend is needed in a short piece of 1 1/4” EMT (4 ft. to 5 ft. in length) sleeve it with a piece of 1 1/2” conduit. This extends the length and provides both solid footing and better leverage. Foot pedal benders can be bench mounted with good results. However, a pipe sleeve should be used over the 11/ 4” EMT or 1” Rigid or IMC. Such a sleeve does two things: (a) Provides greater leverage. (b) Provides close-in-to-the-groove pressure which is so vital to making a good bend.
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Chapter 14
Sub-Section "B" - Rigid conduit and IMC Benders In the late 70s, a new electrical conduit, Type IMC, appeared on the market. IMC stands for Intermediate Metal Conduit. It is steel conduit produced by the continuous electric weld process in trade sizes 1/2” through 4”. IMC meets Underwriters Laboratory specification 1242 and ANSI spec. C-80-6. There are no NE Code limitations on IMC. It is generally accepted for use in locations just like rigid steel conduit. The wall thickness of type IMC is thinner than that of rigid steel conduit but it is thicker than thin wall EMT. Hence, the term Intermediate Metal Conduit. Apprentice electricians are often initiated into conduit bending via the use of thin wall fixed radius benders. These are excellent training tools because stub-ups, offsets, backbends, and saddles can be made accurately if the operator follows the simple rules explained in this manual. Symbols built into these benders by manufacturers serve as indispensable guide marks for accuracy. However, for bending rigid steel conduit or IMC conduit, different hand benders are recommended. Electricians are sometimes tempted to use a 3/4” EMT bender for bending 1/2” rigid or 1/2” IMC conduit. This practice has limitations. Bending rigid conduit or IMC is like fabricating a “double thick” thin wall conduit. The O.D. is larger and the operator must move more than twice the metal to bend it. It follows then, that newly designed benders were needed to bend these heavier conduits to the proper radius. Obviously, existing thin wall benders were not the answer because the grooves did not fit and their radii were too large, resulting in awkward inappropriate looking bends. To safely bend these heavier conduits new tools have been engineered. They have stronger hooks, heavier wall sections, degree scales modified to register with these larger conduit outside diameters. In one bender, even a stouter LP.S. handle is used for extra strength. These new rigid conduit hand benders make the proper NE Code radius bends as per Table 346-10 for a neat, trim professional appearance. Although engineered for rigid steel and IMC conduits, the tools work perfectly for aluminum rigid conduit. A trim radius, with precision, is just as important on aluminum rigid conduit as on rigid steel or IMC conduits.
FIG. 43
Typical rigid/IMC bender.
Fig. 43 illustrates a typical bender for sizes 1/2” and 3/4” rigid steel, aluminum or IMC conduits. The 1”
Hand Bender Types Described
51
size is quite a different problem. The 1” conduits have a wall heavy enough to skip the need for special grooves. Standard existing 1/4’ EMT benders (the type with a two-position booster step) do an excellent job. Many thousands of these two position benders are already in the field. It is the author’s opinion that even the toughest, most rugged “beef-baron” electrician should not attempt to bend size 1/4" IMC or, of course, 1 1/4” rigid steel conduit with hand benders. Hydraulic or mechanically powered benders should be used for sizes 1 W’ and above. So let’s forget hand benders for 1/4" and larger sizes of rigid or IMC. The power leverage required is simply beyond the range of human strength. It is important that crews equipped with these new benders be able to identify them apart from standard EMT benders because rigid/IMC benders will kink or flatten thin wall EMT. One manufacturer uses a painted foot pedal as a means of identification. Another manufacturer plates the entire tool with zinc-chromate to give it a gold colored finish.
Questions
& Answers
Q Should bends with the new rigid/IMC benders be made on the floor? Yes. Operators will find it best to make all bends in rigid and I MC conduit on the floor. Foot pressure is A again paramount for accuracy. Note: If a previous bend prevents the conduit from laying firm and flat on the floor, bend at the edge of a loading dock or stairwell. Or bend on an elevated surface such as a heavy plank so that the previously bent portion is elevated enough for the conduit to lay in free air and thereby provide solid footing for a floor bend.
Q
Can’t I bend 1/2-in. type IMC or rigid conduit over the bender groove, i.e., in the air with the handle end on the floor?
you must keep extra heavy hand pressure close to the groove...otherwise the conduit bends away A Yes...but from the bottom of the groove and this results in an uneven, inaccurate bend. Note: A larger pipe if sleeved over the IMC will serve both as a lever and will assure the close to the groove pressure so necessary when making a bend in the air.
Q What is a “sled·runner” bend? “sled-runner” is trade slang for a 90° bend that has an ugly, uneven arc. If conduit is allowed to bend A Aoutside of the body of a hickey or bender groove the result is a long radius arc fading into a short radius arc. Lack of sufficient pressure to “coin” the metal into a uniform arc results in a “sled-runner.”
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Q Will regular rigid conduit hickeys work okay on type IMC? hickeys will bend IMC, others will flatten it, kink it or chew it to pieces. In any case, IMC bends A Some must be right the first time. IMC is stiffer than standard rigid steel conduit and unlike heavy wall conduit it is difficult to rework it in its bent area.
Q The bending grooves in EMT benders are too wide to provide the side wall support IMC needs to keep it A “in round.” I notice some flattening when I bend IMC in an EMT bender...why?
Jack's "Timely Tips" For a professional looking conduit job, bends should be trim, i.e., MADE TO THE PROPER RADIUS. Bending tools that have been engineered to bend rigid or IMC make NE Code radius bends. (Tools for EMT make awkward outsized radii when used to bend Rigid or IMC.) BEND RIGID CONDUIT AND IMC ON THE FLOOR . If you are right handed apply pressure to the foot pedal with your LEFT FOOT. You will get better footing and feel more secure to have your RIGHT FOOT placed firmly on the conduit and floor. Note: Vice versa if you are a “lefty.”
Bend with a fairly wide stance. The feet should be 28” to 30” apart. This provides better body balance and more power. Foot pressure is paramount...pin the conduit tight to the floor with STIFF LEG FOOT PRESSURE throughout the entire bend.
Hand Bender Types Described 53
Sub-Section "C" - Combination benders There are several good combination hand benders marketed in North America. These tools are designed especially for small sizes of EMT (1/2” and 3/4”) and 1/2” rigid steel or aluminum conduit and the new type IMC. The author has always taken a dim view of universal type tools in the belief that too often they sacrifice important features in order to give them their universal scope...a typical one piece parallel groove type tool is shown in Fig. 44.
This utility tool has several features of value to the electrician. • Short radius arc...for confined, cramped areas. • One piece malleable iron casting. • Bends 1/2” and 3/4” EMT. • Bends 1/2” rigid steel or aluminum conduit. • Bends 1/2” IMC conduit. • 1/2” EMT groove makes a 3” inside radius. • 3/4” EMT groove makes a 4” inside radius.
FIG. 44 Combined bender tool.
• 1/2” rigid conduit or IMC groove makes a 4” inside radius.
• Each groove has its own separately calibrated degree scale. • Brightly painted symbols serve as permanent bench marks to facilitate and encourage precision work. The disadvantage of combination benders is weight. Obviously, double groove tools must be heavier than a single groove model. The model illustrated weighs 4.5 lbs. without the handle. Combo tools are popular for service repair trucks because one tool covers the need for almost every branch circuit conduit bending job that a troubleshooting electrician may encounter. Made in one size only.
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Chapter 14
Sub-Section "D" - Handles for benders and hickeys Several bender manufacturers are now marketing bender handles of high strength steel. The availability of factory engineered handles is good news for the electrical industry. Here’s Here’s why: Strong, “ready-to-go” handles that stay straight, stiff and rigid are important. No operator likes to work with a bent handle. If bent, the chances are it was made from easy bending electrical conduit. A handle made from soft, ductile, easy bending pipe soon bends adjacent to the neck or collar of the bender. A bent handle is not only a hindrance to accurate bending but it transforms a perfectly good bender into an awkward, cumbersome tool to use. A bent handle that works loose is actually unsafe. If a threaded handle backs off as little as one quarter turn during the fabrication of a bend the operator could be thrown off balance, lose his footing and fall. A field made handle using scrap electrical conduit is false economy. Not only does the practice entail excessive labor costs but benders with easy bending handles soon become a counterproductive liability. A handle that stays straight is a real “plus value” on the job because most hand benders are engineered so that a straight up (vertical to the floor) handle indicates a 30° bend has been made in the conduit. This feature is an aid to accuracy and speeds the work. Obviously, Obviously, a bent handle completely negates this important indicating feature. Factory engineered handles are not only made from high yield merchant pipe, but the threads are tapered so they will jam tight before they hit bottom when screwed into the threaded socket of the bender. Once jammed tight the handle stays put until it is removed with a wrench. Factory-made handles give the manufacturer ample space in which to provide the basic bending instructions at point of use. Some manufacturers apply to the handle a large weatherproof, Mylar coated, vinyl bumper sticker type label. Sometimes called a “Zip-Guide,” this label serves as a ready reference to indicate allowances for precision offsets, back bends, and stub lengths. An instruction label on the handle in bold, black letters is a great aid to the electrician. The data is always with him right there where he is doing the work...it encourages precision, speeds the work and eliminates wasted conduit bends that often wind up as scrap on the “oh-oh” pile. The popular 3/4-in. I.P.S. handle sold by some manufacturers has one end expanded for several inches so that this end will sleeve over 1/2-in. rigid conduit, 1/2-in. IMC and 3/4-in. EMT. Thus the handle can be used as a stub straightener on concrete deck work or for trueing up stub lengths into proper position. How did this custom of marketing hand benders and hickeys without a handle ever get started? The history of it is interesting, but before going into the background, imagine yourself going into a hardware store to buy an axe. The clerk hands you the axe head but informs you that you’ll have to provide your own handle. You might well say to yourself, ‘’This gent has lost his marbles.” Here’s how it all got started: Back about 1910 hickey benders were cobbled up on the job out of plumber’s fittings, i.e., a one inch plumber’ plumber’ss pipe “T” fitting was cut away at the side, all sharp edges were then filed down
Hand Bender Types Described 55
smooth (like a bell-mouth) and a short length of stiff 1-in. plumber’s water pipe was screwed into the top hub of the “T.” This served as a handle lever. It was an improvised tool made up of material found on almost any job. They didn’t know what to name it so they called calle d it a “hickey”...and it stuck. Even today one accepted definition given in the dictionary for the word “hickey” is: “any device or gadget whose name is not known or is momentarily forgotten.” forgotten.” Handles are marketed in the U.S.A. and Canada in iron pipe sizes 3/4-in., 1-in., and 3/4”-in. They are engineered to the proper length, reamed and chamfered on the ends, plated or galvanized to prevent rust and corrosion (see Fig. 45).
FIG. 45 Factory-made bender and hickey handles with Zip-Guide as shown.
Questions
Manufacturers report a steady increase in handle sales as industrial maintenance shops and electrical contractors recognize the false economy of making up their own handles from easy bending shop conduit or job scrap.
& Answers
Q What length of handle is recommended for benders and hickeys? A Note: Handles longer than the above are awkward to use and just add unnecessary weight. An extra long handle invites too much pull with the arms and as a consequence foot pressure lessens. The more foot pressure the better the bend.
does a straight up handle (vertical to the floor) indicate a 30° bend on some benders yet on other Q Why brands it may indicate a 45° bend? is so true. The author’s early models were engineered so that a vertical handle indicated a 45° bend. It A This was soon found that this required the operator to reach over so far for the handle at the start that he relaxed his foot pressure on the power step. Therefore the tool was redesigned with easier-to-reach handles. Now that the handles are 15° closer they are easy to reach, and a vertical handle indicates a 30° bend. Incidentally, 30° bends are now very popular for offsets because wire pulling is easier.
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Q How do I correct a handle that turns or backs off even though the threads are fully engaged? A Cut off the threaded end, re-thread the pipe with a very shallow or tapered thread that will jam up tight. Q In making up my own handles what specification pipe should be used? Schedule 40 merchant pipe is available from industrial supply houses. Also high carbon steel railing pipe A is good. One electrical contractor told the author he got so fed up with bent handles that he outfitted every bender and hickey in his shop with handles made from heavy boiler tube.
Q Yes. Plug it inside with a snug fitting solid-steel rod about 18-in long. Drive the rod into place with a sledge. A Then re-chase the threaded end if it was damaged from the hammer blows. If easy bending conduit is used for a handle can’t it be reinforced?
Jack's "Timely Tips" HANDLES: If you make up your own handles use schedule 40 merchant pipe and cut tapered threads (like on steel water pipe). The threaded end should jam down tight BEFORE it bottoms out in the threaded bender socket. A loose fitting handle is unsafe because it can turn in the middle of a bend.
The length of your bender handle is important. Handles should serve as a means to better body balance...not solely as a power lever. If handles are too long they get in the way. They also invite too much shoulder pull which lifts the entire tool and conduit assembly off the floor and kinked conduit results. Soft steel handles of easy bending conduit should be reinforced by driving a smaller pipe (18” long) or a rebar into the threaded end with a sledge.
A Review of Conduit Bending Tips 57
Chapter 15
A Review of Conduit Bending Tips A lot of hands-on information has been presented in the preceding chapters of this book. Now it’s time for a review to jog the memory a bit. If the material doesn’t sound familiar, make sure you go back and read the appropriate chapter again.
Concentric bending Let us agree then that hickeys are the best tool to use for concentric segmental bending. To obtain a smooth even contour each bite or bending increment should be equal in its degree of arc. The total of such increments completes the 90° sweep. Note in the Concentric Bends table on page 40 that all four bends are made to ninety degrees and each is made in nine equal ten degree (l0°) segments or bites. Suggested spacing for reference marks is shown in this drawing for 1/2” and 3/4” conduits. Important: All hickey bends should be made on the floor, using firm foot pressure on the tool with the operator’s shoe wedged tightly against both conduit and hickey. This provides stability and helps control the degree of bend to be made at each segment. It helps if the operator keeps in mind that he must forcefully pin the conduit tight to the floor on every bite. (See more details on hickeys in Chapter Six.) Place reference marks on the conduits prior to bending as detailed in Chapter Six. Each reference mark should be aligned with an arrow on the hickey or any permanent reference point on the tool to assure equal spacing between bites. Guess work or “eye balling” the degree of bend is not advised. If the hickey has no degree of angle indicator it is recommended that the operator gage the first 10° bend using a protractor. In so doing he should fix in his mind the length of stroke it took to make that first 10° arc. Then he should keep repeating that same stroke on subsequent bites. Reason: A protractor is time consuming and once the operator gets “the feel” of a 10° bend, the protractor is no longer necessary. Concentric bending is a challenge to the skill of the operator. Here expertise is paramount because different hickeys vary in kink points, slippage points and may even require different foot control pressures. Following this basic technique the operator will generally produce good looking concentric bends with speed and precision. An unretouched photo of concentric bends made by this method is shown in Fig. 46.
FIG 46 Well-made concentric bends.
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Chapter 15
A digest-review of basic conduit bending tips Professional electricians become “professional” only after comprehensive training and years of experience in the business. It’s like the old Chinese proverb: “New broom sweep clean...old broom knows corners.” “Knowing the comers” is a big plus in any trade. Here are some conduit bending tips the author has learned after many years of talking “conduit” with professional electricians all over the free world. a. Stub-ups in narrow partitions: Bend a 45° or 60° kick in the conduit a few inches away from the partition. This allows the run to enter the partition obliquely. Thus a conduit bend of conventional NE Code radius will enter into an unbelievably narrow partition with room to spare. b. Bending both legs of an offset on the floor: Make the second bend on a slightly raised platform (a 2” x 4” will usually do) or bend at the edge of a loading dock, stairwell, etc. This allows the first bend to hang down in free air. c. Avoid crooked offsets: To eliminate “dog legs” place a chalk line on the conduit...this facilitates alignment with identical registry points on the bender. Thus multiple bends are kept in the same plane. Or bend the second half of the offset just slightly (8° to 10° or less). Then sight down the pipe. If bends are out of line it will be apparent. Now rotate the conduit into correct position and complete the offset...the “dog leg” will disappear. d. Bending with tool in air: Apply hand pressure as close to the groove as possible, even if it is uncomfortable. Keep pressure close ! Tucking conduit under the arm pit helps. To keep body balance allow the tool to rock forward as the bending progresses. e. Bending on floor: Work on hard surfaces...avoid soft sand, deep carpets, etc. A straight (vertical) handle indicates a 30° bend. f. Offsets: Use 30° angle bends where possible. Wires pull easier around 30° bends...and the multiplier to establish distance between 30° bends is simply two times depth. No decimals or fractions to multiply...and a vertical handle is an instant indicator that a 30° bend has been made. g. Foot pressure: Don’t ignore the importance of foot pressure on the treadle step. Constant foot pressure makes for better looking bends and greater accuracy. Pin the conduit tight to the floor throughout the entire arc of the bend. h. Three bend saddles: Make the center 45° bend first. Then make 22 1/2° bends on each leg. i. Marking conduit: Always girdle the conduit 360° with your pencil mark so it won’t disappear from view in the tool no matter which way you turn the conduit. j. If you paint the bender: Don’t obliterate the all important arrow, star-point, tear drop symbol, rim notch, degree scale or multiplier scale. k. Out of shape hooks or grooves: If a rod-buster stretches the hook of the bender pound it back with a sledge hammer or squeeze the groove in a carpenter’s vise until it returns to its original diameter. This applies only if the tool is of malleable iron. l. Uniform long radii: First mark conduit in even increments and bend in even amounts at each mark.
A Review of Conduit Bending Tips 59
Shifting EMT stubs in concrete slab construction One method for shifting thin wall stubs that have missed a partition in concrete slab construction (see Fig. 46). Note that enough concrete around the stub has been chipped away to allow the heel of the bender to fit snugly around the “wandering” stub below the concrete surface. Caution: Do not place the hook-end of the bender around the stub because the slightest bend will lock the hook fast and the tool can’t be removed without destroying the EMT.
FIG 46
Shifting a stub.
Now, with the heel of the bender in place slip a pipe sleeve over the stub...use the sleeve as a lever to assure close-in pressure, thereby forcing the EMT to bend in the groove of the bender until the stub is shifted into the correct position.
60
Chapter 16
Chapter 16
General Bending Information of Value This chapter includes an assortment of informative data relative to electrical conduit. Electrical journeymen should find it interesting and a worthwhile addition to the store of knowledge about their trade. Sub-sections to follow deal with such subjects as: Metric equivalents to our current measurements and how to transpose them...What conduit types are used in other parts of the free world...Foreign electrical terms vs. North American, etc.
A mini guide to metrication for electricians North America is almost alone in the world as an area still sticking with inches, feet, yards, miles, etc. In 1975 the electrical conduit industry in England converted to the metric system. Our conversion, near term, is inevitable. The shift in England was a major one for British manufacturers of electrical conduit, fittings and virtually all manufacturers of accessories in any way related to the electrical construction industry. Figures in this mini-guide are approximate...but they are accurate enough to serve as a rule of thumb guide when converting to metric equivalents is necessary. Note: For “head estimates” remember the following rule of double-one and double-two:
-a meter is 1.1 yards -a liter is roughly 1.1 quarts -a kilogram is 2.2 lbs.
General Bending Information of Value
61
Conduits abroad Because we are rapidly becoming one world the author feels that the modem electrician should know what other nations use as electrical conduit. In England, the United Kingdom, Europe, Ireland, Japan, South America and, indeed, all over the free world (except North America) electrical steel conduits are generally made to the British standard. British conduit sizes since 1975 are manufactured to metric measurements. Sizes are listed by 0.0. rather than by nominal I.D. as is the custom in North America. British standard conduit is thinner in wall thickness than American or Canadian standard rigid conduit or IMC. However, the British conduit wall is slightly heavier than our EMT. The British standard calls for threaded joints but because of its lighter wall, finer, shallower threads are used. Compression fittings such as our EMT couplings and connectors are rarely used. British standards provide for both black enameled and galvanized finishes. No restrictions are placed on bending radii. It is not uncommon to see short 2” inside radius bends in British 20mm (roughly equal to our 1/2” EMC conduit). An extra heavy British conduit is employed for explosion-proof locations (they call it “flameproof locations”). This extra thick walled conduit is called Water Barrel Pipe. British water barrel pipe is not quite as heavy in wall thickness as standard U.S. or Canadian rigid steel conduit. While British standard conduit is listed in MM sizes for all practical purposes conduit usage is limited to what we would term 1/2”, 3/4” and 1” sizes. Larger sizes comparable to our 1”, 1 1/2” and 2” are not stocked by British electrical whole-salers. These larger sizes are usually shipped directly from the conduit mill. Sizes larger than 2” are strictly mill run specials in the U.K. For conduits larger than the 2” 0.0., 2” x 2” or 2” x 3” steel duct is used. This they call “Trunking.” Cable tray is also popular for heavier feeders and for interior distribution lines. Clay tile conduit or heavy steel armored and jacketed cables are used for underground lines or for direct earth burial. In Switzerland steel electrical conduit is used almost entirely as a mechanical protection for the PVC jacketed cable it houses. Because steel conduit is not used as a ground path in the system the conduit is simply a means of protecting the wires or cables from mechanical injury. For example, on exposed surface runs for lighting, etc. if a 90° turn in the run is required they terminate the conduit, make a 90° bend in the cable, leave the bent cable exposed in free air before it enters another steel conduit at 90° to the first. No threads are cut on conduit ends. They simply cut off the conduit, ream it and insert a plastic end bushing to protect the cable from abrasion. The bushings are driven into the conduit ends for a friction fit. Offsetting small conduits in some instances is done by the wrinkle bend technique. This permits a light gauge steel conduit or tubing to be bent by hand without kinking. A special jumbo size plier is used to bend it. Also available in Switzerland is manufactured prewrinkled PVC conduit. This tubing is rather stiff but it can be hand bent because the wall is thin and it has wrinkles girdling it 360°, i.e., completely around its circumference. Sections of this tubing are inserted into the steel conduit run where necessary to accomplish 90° bends, offsets,
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and saddles. Since the metallic conduit is not used as a ground path these semi-rigid PVC “sections” can be inserted into the run at any point to join the metal conduit via the use of a simple unthreaded metal sleeve type coupling for a friction fit. Manufactured short elbows are used as well as the above. These are made of die cast metal. Where wires emerge from the cut conduit ends, such as at junction boxes, 90° turns, etc. a plastic bushed insert is used to protect the wires from abrasion, sharp edges or wear due to vibration. All conduits and fittings the author saw in Switzerland were galvanized or plated. To sum up, branch circuit work is 220V AC and wired with multi-conductor jacketed PVC cables with the ground conductor within the cable rather than employing the raceway as a ground path.
American vs. British terminology Not long ago the author licensed an English firm to produce the British counterpart to his patented line of hand bending tools. On visits to the U.K. to help them introduce the technique he was confused by British electrical expressions. He soon discovered that it was not the English accent as much as the different expressions, slang and jargon they use that make it difficult at first for North American Electricians to understand their British counterparts. To help the would-be International Electrician understand these “foreign” expressions there is listed below a sampling of American vs. British terms...Are they better?...worse?...amusing?-you decide!
North American
British (U.K.)
Angle bend
Set
Blank cover
Blanking plate
Chase nipple
Smooth bore bush
Conduit hickey
Hickey bar
Conduit bodies
Inspection boxes
Cord cap
Plug top
Cord connecto
Extension socket
Conduit bushing
Ring bush
Duct work (4” x 4”)
Trunking
Duplex receptacle
Twin socket outlet
General Bending Information of Value Electrical metallic tubing
Slip conduit
Electric water heater
Electric geyser
Elevator
Lift
Exhaust fan
Extractor fan
Explosion proof
Flame proof
Flashlight
Electric torch
Floor lamp
Standard lamp
Ground fault detector
Earth leakage trip
Grounding lug
Earthing clamp
Ground wire
Earth wire
light pole
Lamp stand
light fixtures.
light fittings
Locknut
Back nut
Moonlighter
Nixer
Offset
Double set
Panel board
Consumer unit
Pick-up truck
Service lorry
Pipe straps
Fixits
Porcelain pull socket
Ceiling rose
Rigid steel conduit
Water barrel pipe
Toggle switch
Rocker switch
Unit heater
Blow heater
2-Hole pipe strap
Pipe saddle
3-Bend saddle
Bubble set
4-Bend saddle
Cross-over bend
4-Burner range
4-Ring cooker
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Non-electrical terminology NorthAmerican
British (U.K.)
A buck
A quid
A goof
A clanger
Beat up jalopy
Clapped out car
Bikinis
Beach briefs
Blew his stack
Went up the spout
Candy store
Tuck shop
Chea
Fiddle
Cops
Narks
Crummy
Scruffy
Detour
Road works diversion
Duped
Winkled
Eager beaver
Pushy chap
Efficiency apartment
Bed sit
Fat salary
Good screw
Fill ‘er up
Top it off
Finagled
Diddled
Give him a blast
Give him a rocket
Good grub
Good nosh
Goofing off
Hanging about
Ground beef
Beef mince
Gutters
Rone pipes
Gypsies
Tinkers
General Bending Information of Value
Head cold
Thick in the clear
Highway rest area
Motorway lay by
Honey
Treacle
Hot rod car
Hotted up speedster
Ice cream cone.
Pokey hat
Keg of beer
Drum of bitter
Make it snappy
Nip it up straight away
Mugged
Coshed
Napkin
Serviette
Needled
Nobbled
On a binge
On a pub crawl
Overpass
Fly over
Pressured
Lumbered
Ready to wear
Off the peg
S-curve
Double bend
Scram
.Buzz off
Shopping bag
Carrier
Shopping cart
Market trolley
Side burns
Side chops
Soft berth
Plum job
Spuds
Teddys
Station wagon
Shooting brake
Street hawke
Busker
Taxi stand
Cab rank
Teed off
Brassed off
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The “john”
The “loo”
Ticketed (traffic)
Blistered
Tight as a tick
Tiddled as a coot
Traffic circle
Round-a-bout
Trash can
Dust bin
Tricky
Dicey
Whacky
Loopy
Windshield
Windscreen
