6.-2.
'ecommended 0eed Per (ooth #igh-speed +"tters$ Sample (ale Face See (ale 6.%2 in (e:t Mills
Helical Mills
Material
in"
!!
&lloy steel
""!
"15 ""5
&luminum
"22
"55
Slotting and Side Mills in" !! in" "12 ""' "1
"1. "'5 "1* "**
+rass and bron,e medium3 /able"1' "*5 "11 "2. "". shows feed per tooth for roughing cuts – "2 -ast iron for finishing cut( the feed per tooth would be reduced or even !6> of value medium3 "1*to!65 "** "1" "25 shown "") "1.
6.-2/
deal 'ate o 0eed • Work advances into cutter( each successive tooth advances into work e:ual amount – Croduces chips of e:ual thickness • ,eed per tooth
,eed E no= of cutter teeth F feed6tooth F cutter r6min ,eed 8in=6min9 E G F &C/ F r6min
6.-22
:amples; 0eed +alc"lations nch +alc"lations 0ind the eed in inches per min"te "sing a 3%5 in% diameter /2 tooth helical c"tter to c"t machine steel #+S).$
,irst( calculate proper r6min for cutterB r 6 min
< xCS =
D
< x"$ =
>=@
=
?!
,eed8in6min9 E G F &C/ F r6min E!5 F =$!$ F ?! E !$=? or !! in6min
6.-23
7irection o 0eed; +on,entional • 'ost common method is to feed work against rotation direction of cutter
6.-24
7irection o 0eed; +liming • When cutter and workpiece going in same direction • &utting machine e:uipped with backlash eliminator • &an increase cutter life up to @$
6.-25
1d,antages o +lim Milling • Ancreased tool life 8up to @$9 – &hips pile up behind or to left of cutter
• Iess costly fiFtures re:uired – ,orces workpiece down so simpler holding devices re:uired
• Amproved surface finishes – &hips less likely to be carried into workpiece
6.-26
1d,antages o +lim Milling • Iess edge breakout – /hickness of chip tends to get smaller as nears edge of workpiece( less chance of breaking
• -asier chip removal – &hips fall behind cutter
• Iower power re:uirements – &utter with higher rake angle can be used so approFimately 5$ less power re:uired
6.-2&
7isad,antages o +lim Milling • 'ethod cannot be used unless machine has backlash eliminator and table gibs tightened • &annot be used for machining castings or hot0rolled steel – Hard outer scale will damage cutter
6.-2)
7epth o +"t • ;oughing cuts should be deep – ,eed heavy as the work and machine will permit – 'ay be taken with helical cutters having fewer teeth
• ,inishing cuts should be light with finer feed – epth of cut at least =$!@ in= – ,eed should be reduced rather than cutter speeded up
PowerPoint to accompany
Technology o Machine Tools !th "dition
Krar • Gill • Smid
#nd Mills Unit !1
Copyright © The McGraw-Hill Companies, Inc.
6/-3.
Objectives • 4ame two types of material of which end mills are made and state their application • Describe the purpose of two6ute and multiple6ute end mills • 7now the purpose of climb and conventional milling
6/-3/
nd Mills • 1reatly improved since days of carbon0steel cutting tools • High0speed steel 8H779 cutting tools maintain very important place in metal0 cutting industry • Variables influencing cutter decision – Cart shape( work material( wear resistance of tool( red hardness( machine condition
6/-32
igh-Speed nd Mills • ;elatively ineFpensive( easy to get and do 4obs :uite well • &apable of machining with close tolerances • 7ingle most versatile rotary tools used on conventional and &G& machines • Af need harder tool( fre:uent solution is cobalt end mill – Iess eFpensive than carbide( long tool life
6/-33
+aride nd Mills • &arbide properties vs= H77 tool materials – Higher hardness – 1reater rigidity – &an withstand higher cutting temperatures
• &an run at higher speeds and feeds – Ancreasing production rates – Croviding long tool life
• High0performance tool material
6/-34
+ommon Machining !perations Cerformed with H77( cobalt( solid carbide( or indeFable insert type end mill • Open and closed pockets • ,acing operations for small areas • &ounterboring and spotfacing
• Ceripheral end milling • 'illing of slots and keyways • &hannel groves( face grooves and recesses • &hamfering
6/-35
nd Mill 0orms • 1round into re:uired shapes – ,lat bottom end mill 8most common9 • Used for all operations re:uiring flat bottom and sharp corner between wall and bottom
– -nd mill with full radium 8ball nose end mill9 • Used for > machining of various surfaces
– -nd mill with corner radium 8bull nose end mill9 • Used for either > work or for flat surfaces that re:uire corner radius between wall and bottom
6/-36
Three common types and the relationship of the radius to the tool diameter.
6/-3&
+ommon (ypes o nd Mills • /wo0,lute -nd 'ill – Have large( open flutes that provide eFcellent chip flow – ;ecommended for general0purpose milling – Jlways select shortest end mill possible for 4ob to obtain maFimum tool rigidity – &an have different length lips on end • 'ill slots( keyways( plunge cut and drill shallow holes
6/-3)
+ommon (ypes o nd Mills • /hree0,lute -nd 'ill – With end teeth – Used to plunge into workpiece – Used to mill slots( pockets and keyways – 'inimize chatter and better chip removal
• ;oughing -nd 'ill – esigned to provide best performance while machining broad range of materials – Jllows deeper cuts at faster feed rates
6/-39
7irection o +"t; +lim • &utter rotation and table feed going in same direction • Vertical millingB cutter tendency to pull work into cutting flutes • Horizontal millingB cutter pushes work against table • 'aFimum thickness of chip occurs at beginning of cut and eFits when thin – ;esult – chip absorbs heat generated
6/-4.
7irection o +"t; +on,entional • When cutter rotation and table feed are moving in opposite directions – Has tendency to pull or lift workpiece up from table
• Amportant that work be held securely
6/-4/
7irection o +"t
6/-42
Milling +"tter 0ail"re • -Fcessive heat – One of main causes of total cutting edge failure – &aused by cutting edges rubbing on workpiece and chips sliding along faces of teeth – -ver0eFpanding cycle – 'inimized by correct speeds( feeds( and coolant
• Jbrasion – Wearing0away action caused by metallurgy of workpiece – dulls cutting edges and cause Kwear landsK
6/-43
+hipping or +r"mling o +"tting dges • 7mall fractures occur and small areas of cutting edges chip out when cutting forces impose greater load on cutting edges – 'aterial left uncut imposes greater cutting load – &ondition progressive • Once started will lead to total cutter failure
• ull edges increase friction( heat( and horsepower re:uirements
6/-44
+logging • 7ome workpiece materials have KgummyK composition – &hips long( stringy and compressible
• &hips clog or 4am into flute area • 'inimize by reducing depth or width of cut( reducing ,C/( using tools with fewer teeth( creating more chip space and coolant – &oolant applied under pressure to flush out flute area
6/-45
PowerPoint to accompany
Technology o Machine Tools !th "dition
Krar • Gill • Smid
Vertical Mill Operations Unit !2
Copyright © The McGraw-Hill Companies, Inc.
62-4&
Objectives • &lign the vertical head and vise to within 8""1 in ""2 mm3 • nsert and remove end mills from spring collets • &ccurately machine a bloc s:uare and parallel • Drill holes to an accurate location
62-4)
Vertical Milling Machine • Versatile and easy setup • Cerforms wide variety of operations – -nd milling( face milling – .eyway and dovetail cutting – /0slot and circular slot cutting – 1ear cutting( drilling( boring( reaming
• &utting tools used relatively small so cost lower
62-49
1ligning the Vertical head •
Head must be s:uare to table 8?$L9 Proced"re to chec= spindle alignment != 'ount dial indicator on suitable rod( bent at ?$L and held in spindle 5= Cosition indicator over front * aFis of table >= &arefully lower spindle until indicator button touches table and dial indicator registers no more than M revolutionN set bezel to zeroN Iock spindle in place
62-5.
<= &arefully rotate spindle !"$L by hand until button bears on opposite side of tableN &ompare readings @= Af differences( loosen locking nuts on swivel mounting and ad4ust head until indicator registers approFimately difference between two readingsN /ighten locking nuts #= ;echeck accuracy of alignment D= ;otate vertical mill spindle ?$L and set dial indicator as in step >
62-5/
"= ;otate machine spindle !"$L( check reading at other end of table ?= Af two readings do not coincide( repeat step @ until readings are same !$= /ighten locking nuts on swivel mount !!= ;echeck readings and ad4ust if necessary
62-52
1ligning the Vise • When vise aligned on vertical milling machine( dial indicator may be attached to :uill or head by clamps or magnetic base • 7ame method of alignment followed as outlined for aligning vise on horizontal milling machine
62-53
+ollets • Hold end mills( cutting tools and accessories in machine spindle • 7pring collet – Culled into spindle by draw0bar that closes on cutter shank – riven by means of friction between collet and cutter
• 7olid collet • 'ore rigid • Culled into spindle by draw0bar • riven by setscrews that bear against flats of cutter shank
62-54
(o Mo"nt a +"tter in a Spring +ollet !=
7hut off electric power to machine
5=
Clace proper cutter( collet( and wrench on piece of masonite( wood( or soft plastic on table
62-55
>= <= @= #=
&lean taper in machine spindle Clace draw0bar into hole in spindle top &lean taper and keyway on collet Ansert collet into spindle bottom( press up( and turn until keyway aligns with key in spindle D= Hold collet up with one hand and with other( thread draw0bar clockwise into collet "= Hold cutting tool with cloth and insert it into collet for full length of shank ?= /ighten draw0bar into collet 8clockwise9 by hand !$= Hold spindle brake lever and tighten draw0bar tightly as possible with wrench
62-56
Proced"re to 'emo,e +"tter rom a +ollet •
Operation for removing cutting tools similar to mounting( but in reverse order != 7hut off electric power to machine 5= Clace piece of masonite( wood( or soft plastic on machine table to hold necessary tools >= Cull on spindle brake lever to lock spindle( loosen draw0bar with wrench 8counterclockwise9
62-5&
<= Ioosen draw0bar( by hand( only about three full turns @= Hold cutter with cloth #= With soft0faced hammer( strike down sharply on head of draw0bar to break taper contact between collet and spindle D= ;emove cutter from collet "= &lean cutter and replace it in its proper storage place where it will not be damaged by other tools
62-5)
Machining a *loc= S8"are and Parallel •
Amportant that each side be machined in definite order
Machining Side /
!= &lean vise thoroughly and remove all burrs from workpiece( vise and parallels 5= 7et work on parallels in center of vise with largest surface 8side !9 facing up
59-59
62-6.
Proced"re to Machine an 1ng"lar S"race != Iay out angular surface 5= &lean vise >= Jlign vise with direction of feed •
Utmost importance
<= 'ount work on parallels in the vise
62-6/
@= 7wivel vertical head to re:uired angle #= /ighten :uill clamp D= 7tart machine and raise table until cutter touches work •
;aise table until cut desired depth
"= /ake trial cut for about =@$ in= ?= &heck angle with protractor !$= Af angle correct( continue cut !!= 'achine to re:uired depth( taking several cuts if necessary
62-62
>= With center drill spot each hole to be tapped to slightly larger than tap diameter <= rill hole to correct tap drill size for size of tap to be used @= 'ount stub center in drill chuck
62-63
Slots and Keyseats •
'ay be cut in shafts more easily on vertical milling machine( using a two0 or three0fluted end mill
Proced"re or +"tting
!= Iayout position of keyseat on shaft( and scribe reference lines on end of shaft
62-64
#= Iower table until cutter clears workpiece D= 'ove table over amount e:ual to half diameter of shaft plus half diameter of cutter plus thickness of paper
62-65
62-66
PowerPoint to accompany
Technology o Machine Tools !th "dition
Krar • Gill • Smid
Hori$ontal Milling Machines and %ccessories Unit !'
Copyright © The McGraw-Hill Companies, Inc.
64-6)
Objectives • ;ecogni,e and e
64-69
+lassiication o ori>ontal Milling Machines != 'anufacturing0type •
&utter height is controlled by vertical movement movement of headstock
5= 7pecial0type •
esigned for specific milling operations
>= .nee0and0column0type •
;elationship between cutter height and work controlled by vertical movement of table
64-&.
Plain Man"act"ring (ype Milling Machine
64-&/
+ross section o a +incinnati Machine *ac=lash liminator
64-&2
1rors +ollets and 1dapters
64-&3
Vises ?ni,ersal Vise Plain Vi Vise se
Swi,el *ase Vise
64-&4
0i:t"ring Systems
asy-to-ad@"st Stop
A"ic=-change sel-loc=ing system
64-&5
nde:ing or 7i,iding ead • Cermits cutting of bolt heads( gear teeth( ratchets • ;evolve work as re:uired to cut helical gears and flutes in drills( reamers( and other tools – When connected to lead screw of milling machine
PowerPoint to accompany
Technology o Machine Tools !th "dition
Krar • Gill • Smid
Milling Cutters Unit !5
Copyright © The McGraw-Hill Companies, Inc.
65-&&
Objectives • dentify and state the purposes of si< standard milling cutters • dentify and state the purposes of four specialpurpose cutters • Use highspeed steel and carbide cutters for proper applications
65-&)
Plain Milling +"tters • 'ost widely used • &ylinder of high0speed steel with teeth cut on periphery • Used to produce flat surface • 7everal types – Iight0duty – Iight0duty helical – Heavy0duty – High0heliF
65-&9
Bight-7"ty Plain Milling +"tter • Iess than P in= wide( straight teeth • Used for light milling operations • /hose over P in have heliF angle of 5@L – /oo many teeth to permit chip clearance
65-).
ea,y-7"ty Plain Milling +"tters • Have fewer teeth than light0duty type – Crovide for better chip clearance
• HeliF angle varies up to <@L – Croduces smoother surface because of shearing action and reduced chatter
• Iess power re:uired
65-)/
igh-eli: Plain Milling +"tters • Have heliF angles from <@L to over #$L • 7uited to milling of wide and intermittent surfaces on contour and profile milling • Usually mounted on milling machine arbor – 7ometimes shank0mounted with pilot on end and used for milling elongated slots
65-)2
Standard Shan=-(ype elical Milling +"tters • &alled arbor0type cutters • Used for – 'illing forms from solid metal – ;emoving inner sections from solids
• Anserted through previously drilled hole and supported at outer end with type J arbor support
65-)3
Side Milling +"tters • &omparatively narrow cylindrical milling cutters with teeth on each side and on periphery • Used for cutting slots and Straight for face and straddle milling operations • ,ree cutting action at high Staggered speeds and feeds • 7uited for milling deep( narrow slots
65-)4
al-Side Milling +"tters • Used when only one side of cutter re:uired • Jlso make with interlocking faces so two cutter may be placed side by side for slot milling • Have considerable rake – Jble to take heavy cuts
65-)5
0ace Milling +"tters • 1enerally over # in= in diameter – Have inserted teeth made of high0speed steel held in place by wedging device
• 'ost cutting action occurs at beveled corners and periphery of cutter • 'akes roughing and finishing cuts in one pass
65-)6
Shell nd Mills • ,ace milling cutters under # in= • 7olid( multiple0tooth cutters with teeth on face and periphery • Held on stub arbor – 'ay be threaded or use key in shank to drive cutter
65-)&
1ng"lar +"tters • 7ingle0angle – /eeth on angular surface – 'ay or may not have teeth on flat – <@L or #$L
• ouble0angle – /wo intersecting angular surfaces with cutting teeth on both – -:ual angles on both side of line at right angle to aFis
65-))
(ypes o 0ormed +"tters
+onca,e
+on,e:
Gear (ooth
65-)9
Metal-Slitting Saws
65-9.
(-Slot +"tter • Used to cut wide horizontal groove at bottom of /0slot – Jfter narrow vertical groove machined with end mill or side milling cutter
• &onsists of small side milling cutter with teeth on both sides and integral shank for mounting
65-9/
7o,etail +"tter • 7imilar to single0angle milling cutter with integral shank • Used to form sides of dovetail after tongue or groove machined • Obtained with <@L( @$L( @@L( or #$L angles
65-92
• Used for milling semicylindrical keyseats in shafts • esignated by number system
PowerPoint to accompany
Technology o Machine Tools !th "dition
Krar • Gill • Smid
Milling Machine Setups Unit !!
Copyright © The McGraw-Hill Companies, Inc.
66-94
Objectives • /ount and remove a milling machine arbor • /ount and remove a milling cutter • &lign the milling machine table and vise
66-95
Milling Machine Saety != 2e sure work and cutter are mounted securely before taking cut 5= Jlways wear safety glasses >= When mounting or removing milling cutters( always hold them with cloth to avoid being cut <= When setting up work( move table as far as possible from cutter to avoid cutting your hands
66-96
@= 2e sure cutter and machine parts clear work #= Gever attempt to mount( measure( or ad4ust work until cutter completely stopped D= .eep hands( brushes( and rags away from revolving milling cutter at all times "= o not use an eFcessively heavy cut or feed •
&ause cutter to break and fly apart
66-9&
?= Jlways use brush( not rag( to remove cuttings after cutter has stopped revolving !$= Gever reach over or near revolving cutter •
.eep hands at least !5 in from revolving cutter
!!= .eep floor around machine free from chips( oil( and cutting fluid
66-9)
Milling Machine Set"ps != &heck if machine surface and accessory free from dirt and chips prior to mounting 5= o not place tools( cutters( or parts on milling machine table >= Use keys on all but slitting saws when mounting cutters
66-99
<= &heck that arbor spacers and bushings clean and free from burrs @= When tightening arbor nut( take care to only hand tighten •
Hammer or wrench will strip threads and bend or damage accessory or part
#= When mounting work in vise( tighten vise securely by hand and tap into place with lead or soft0faced hammer
PowerPoint to accompany
Technology o Machine Tools !th "dition
Krar • Gill • Smid
The &nde'ing, or Dividing, Head Unit !. Copyright © The McGraw-Hill Companies, Inc.
6)-/./
Objectives • -alculate and mill 6ats by simple and direct inde
6)-/.2
nde:ing #7i,iding$ ead • One of most important attachments for milling machine • Used to divide circumference of workpiece into e:ually spaced divisions when milling gears( splines( s:uares and heFagons • Jlso used to rotate workpiece at predetermined ratio to table feed rate
6)-/.3
nde: ead Parts • Headstock with indeF plates • Headstock change gears • Quadrant
• Universal chuck • ,ootstock • &enter rest
