manufacturing lecture

G D & T

GD&T Geometrical Dimensioning & Tolerancing

Based on the ASME Y14.5M 1994 Dimensioning and Tolerancing Standard

G D & T

What is is G D & T ? GD & T is a Standardised & precise

mathematical mathematical language of Symbols, Rules, Definitions & conventions for Engineering drawings that more clearly defines the dimensional and tolerance requirements with respect to the actual function and relationship of features. GD & T is the grammar of engineering Drawing GD &T describes the product’s functional

interfaces with mating parts and assemblies etc. GD &T provides documentation base for design

of production and quality systems. GD &T is also a design philosophy on how to

design and dimension the parts. GD & T encourages a dimension philosophy

called Functional Dimensioning which means – ””Define a part based on how it functions in the final product””.

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Dimensioning Standards ASME Y14.5M-1994 American Society of Mechanical Mechanical Engineers. Y14.5 --The standard number M--Indicate the standard is in Metric 1994--Year of approved

History

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Basics Eng ngin ine eeri ring ng Drawing rawing:: Engineering drawing is a document /tool that communicates the design and manufacturing information of a part. Drawing is the universal language of engineering. Engineering drawing provides the following information: a. Geometry of the part. ( Shape, Size and Form of the part). b. Critical functional relationship. c. Tolerances allowed for proper functioning. d. Material, Heat treatment and surface coating info. e. Part documentation information (Part No. and Rev. Level etc.)

Engin ng ine eering ri ng dra dr awing wi ng shoul sh ould d be pre pr ecise cis e and correct. correct. Poor drawing drawing results results in : a. Wastage of Money, time and material. b. Unhappy Customers.

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What are Dimensions?

Dimension is a numerical value expressed in appropriate units of measure and used to define the size, location, orientation, from, OR other geometric characteristics characteristics of the part. What are Tolerances?

Tolerance is the total amount that feature of the part are permitted permitted to vary from the specified specified dimension. Types of Tolerances:

1. Limit tolerance 2. Plus-minus tolerance a. Unilateral Tolerance b. Equal bilateral Tolerance c. Unequal bilateral or Limit Tolerance

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Benefi Bene fits ts of G D & T ? Improve mpr oves s Communi omm unica catio tion n: GD &T provides uniformity in drawing specifications and interpretation. Increa nc reases ses Pro Produ duct ctio ion n Tol Tole erance: GD &T provides Bonus or Extra Tolerance for manufacturing. This extra tolerance can make a significant saving in production costs. Better Better Pro Produ duct ct Desi Design gn:: Dimensioning based on how the part will be functioning at the final stage

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GD & T Im p o r t an t Ter Ter m s 1) Fe Featu aturr e & Size Feature: Feature: Any surface surface on a part part or Physical Physical Portion of of a part. part.

Fea Feature tu re of size si ze::

Can be used to establish an axis, Median Plane or Center point

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GD & T Im p o r t an t Ter Ter m s 2) Ba Basic sic dimension d imension Basic Basic dimension dimension  A basic dimension is a numerical value used to describe the theoretically exact size, profile orientation or location of a feature or datum target. These dimensions have no tolerance. They only  locate the tolerance zone.  These dimensions are enclosed in a rectangular box.

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GD & T Im p o r t an t Ter Ter m s 3) Featu ture re Con Contr trol ol Frame Defines Geometric Characteristics Symbol, Tolerance Value with Modifiers and Datum Information

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GD & T Im p o r t an t Ter Ter m s 4) Mod Modif ifiers iers M MMC : Maximum Material Condition : For For Hole Hole ----- Smal Smalle lest st diam diamet eter er For shaft shaft --- Larges Largestt diamet diameter. er. L LMC : Least Material Condition : For For Hole Hole ----- Larg Larges estt diam iameter eter For shaft shaft --- Smalle Smallest st diamet diameter er S RFS : Regardless of Feature Size : If MMC or LLC is not mentioned tolerances are applied RFS . When the part deviates in size from the specified condition of MMC or LMC, equal amount of additional additional (BONUS) tolerance is added to the geometrical tolerance. Other Modi odifiers fiers

Ex tre tr em e Var i at i ons on s of Form or m Al A l l o w ed B y Size Si ze Tol To l eran er anc ce 25.1 25

25 (MMC)

25.1 (LMC)

25.1 (LMC)

25 (MMC)

MMC Perfect Form Boundary

25.1 (LMC)

In t er n al Feat u r e o f Si ze

Ex tre tr em e Var i at i ons on s of Form or m Al A l l o w ed B y Size Si ze Tol To l eran er anc ce 25 24.9

24.9 (LMC)

25 (MMC)

24.9 (LMC)

MMC Perfect Form Boundary

25 (MMC)

24.9 (LMC)

Ex t er n al Feat u r e o f Si ze

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GD & T Im p o r t an t Ter Ter m s 5) Geometric Characteristics

Symbols

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Symbols

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Symbo ym bols ls Dime im ensio ns ions ns

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Symbo ym bols ls Dim Dime ensio ns ion n

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Symbols ymb ols Use - exampl xample es

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Tolerances o f Form St r ai g h t n es s (ASME Y14.5M-1994, 6.4.1)

Fl at n es s (ASME Y14.5M-1994, 6.4.2)

Ci r c u l ar i t y (ASME Y14.5M-1994, 6.4.3)

Cy l i n d r i c i t y (ASME Y14.5M-1994, 6.4.4)

• Form Charact Characterist eristics ics are always always individua individuall ie not related to datum. • Form controls do not directly control a feature’s size. • A feature’s form tolerance must be less than it’s size tolerance

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Straightness (Fl at Su r f ac es ) It is i s the t he dista dist ance between between t wo para parallel llel pla pl anes spaced apart a distance equal equal to the stra str aigh ightness tness tolera t olerance nce 0.5

0.1

25 +/-0.25

0.1 Tolerance 0.5 Tolerance

Straight ness is th e con condit dition ion where an an element element of a surface sur face or an axis axis is i s a str stra aigh ightt line lin e

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Straightness (Fl at Su r f ac es ) 0.5 Tolerance Zone

25.25 max 24.75 min

0.1 Tolerance Zone

In this example each line element of the surface must lie within a tolerance zone defined by two parallel lines separated by the specified tolerance value applied to each view. All points on the surface must lie within the limits of size and the applicable straightness limit.

The straightness tolerance is applied in the view where the elements to be controlled are represented by a straight line

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St r ai g h t n es s (RFS) 0.1

0.1 Diameter Tolerance Zone MMC

Outer Boundary (Max)

Outer Bou ndary nd ary = Actu Ac tual al Fea Featu ture re Size Size + Straigh tness tn ess Tol Tolerance erance

In this example the derived median line of the feature’s actual local size must lie within a tolerance zone defined by a cylinder whose diameter is equal to the the specified tolerance value value regardless regardless of the feature size. Each circular element of the feature must be within the specified limits of size. However, the boundary of perfect form at MMC can be violated up to the maximum outer boundary or virtual condition diameter.

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St r ai g h t n es s (MMC) 15 14.85 0.1 M

15 (MMC)

0.1 Diameter Tolerance Zone

15.1 Virtual Condition 14.85 (LMC)

0.25 Diameter Tolerance Zone

15.1 Virtual Condition Virtual Virt ual Cond Condit ition ion = MMC MMC Feature Feature Size Size + Straightn Straigh tness ess Tol Tolerance erance

In this example the derived median line of the feature’s actual local size must lie within a tolerance zone defined by a cylinder whose diameter is equal to the specified tolerance value at MMC. As each circular element of the feature departs from MMC, the diameter of the tolerance cylinder is allowed to increase by an amount equal to the t he departure from the local MMC size. Each circular element of the feature must be within the specified limits of size. However, the boundary of perfect form at MMC can be violated up to the t he virtual condition diameter.

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Flatness 0.1

25 +/-0.25

0.1 Tolerance Zone 0.1 Tolerance Zone

24.75 min

25.25 max

In this example the entire surface must lie within a tolerance zone defined by two parallel planes separated by the specified tolerance value. All points on the surface must lie within the limits limits of size size and the flatness flatness limit limit..

Flatness is the condition of a surface having all elements in one plane. Flatness must fall within the limits of size. The flatness tolerance must be less than the size tolerance.

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Circularity (Roundness) 0.1

90

0.1 90

0.1 Wide Tolerance Zone

In this example each circular element of the surface must lie within a tolerance zone defined by two concentric circles separated by the specified tolerance tolerance value. All points on the surface must lie within the limits limits of size and and the circulari circularity ty limit. limit.

Circularity is the condition of a surface where all points of the surface intersected by any plane perpendicular to a common axis are equidistant from that axis. The circularity tolerance must be less than the size tolerance

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Cylindricity 0.1

0.1 Tolerance Zone

MMC

In this example the entire surface must lie within a tolerance zone defined by two concentric cylinders separated by the specified tolerance value. All points on the surface must lie within the limits of size size and the cy cylin lindri dricit city y limit. limit.

Cylindricity is the condition of a surface of revolution in which all points are equidistant from a common axis. Cylindricity is a composite control of form which includes circularity (roundness), straightness, and taper of a cylindrical feature.

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To l er an c es o f Orientation An gu l ari ar i t y (ASME Y14.5M-1994 ,6.6.2)

Perpendicularity (ASME Y14.5M-1994 ,6.6.4)

Parallelism (ASME Y14.5M-1994 ,6.6.3)

Orientation Characteristics are always related to datum

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Datum tu m defi defini niti tion on ? Datums are imaginary perfect points, axes and planes established from actual part features. (Datum ( Datum features). features ). These perfect geometric references act as origins of measurement. These imaginary Datums do not exist in the real world. They are simulated with manufacturing and inspection equipments such as machine tables, chucks, surface plates, angle plates and vee blocks. We then orient or locate other feature surfaces, axes, centre planes or tangent planes from these simulated datum points, axes and planes. Datums define the sequence in which part is to contact the inspection equipment for dimension measuremen measurement. t. Datums Datums define the part part surfaces surfaces which are to contact the inspection equipment for dimension measurement. Some times instead of entire surfaces, Datum target points, points , Datum tu m ta t arget lin l ine es or Datu Datum m target targ et areas areas are used for establishing Datums .

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Dat u m …. Im p o r t an t Ter Ter m s …

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Datum tu m Tar gets… gets …. Imp Impor ortant tant Terms rm s

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Datum features are chosen based on part functionality and their interrelationships with mating features. Datum features should be Functional Functional Representative of mating or seating features and or alignment edges. Ac A c c ess es s i b l e to those in manufacturing and inspection Repeatable from dept to dept Primary datum d atum Plane: Plane: is established from at least 3 high points of contact on the actual part surface. (2 Rotational and 1 linear degree of freedom are arrested). Secondary con dary datum plane: plane: is established from at least least 2 high points of contact on the actual part surface while the part maintains it’s high points of contact with primary datum plane. The secondary datum plane is simulated perpendicular to the first. One more rotational r otational and one more linear degrees of freedom are arrested. Tertia rti ary datum p lane is constructed perpendicular to the first two. It is establishing from contacting at least one high point on the actual part surface. This is done while the part maintains it’s contact with the primary and datum feature simulators. The tertiary datum arrests the remaining linear degree of freedom.

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Inte nt er pre pr etat tat ion io n of Datum tu m

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Inte nt erpr rp r et ation ti on of Dat um

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An A n g u l ari ar i t y (Feature Surface to Datum Surface) 20 +/-0.5 0.3 A 30 o

A 19.5 min

20.5 max

30 o

A


30 o

A


The tolera tol erance nce zone zone in this thi s example is d efined fin ed by two parallel parallel planes oriente ori ented d at at the specifi ed angle angl e to t he datum r eference ference plane.

Angularity is the condition condition of the planar feature surface at a specified angle (other than 90 degrees) to the datum reference plane, within the specified tolerance zone.

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An A n g u l ari ar i t y (Feature Axis to Datum Surface) NOTE: Tolerance applies to feature featur e at at RFS RFS 0.3 A

0.3 Circular Tolerance Zone


60 o

A

The tolerance zone zone in this thi s exampl example e is defined by a cylind cyl inder er equal equal to t he lengt length h of t he fea feature, tur e, oriente ori ented d at the specif ied angle to the datum reference reference plane.

A

Angularity is the condition condition of the feature axis at a specified angle (other than 90 degrees) to the datum reference plane, within the specified tolerance zone.

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An A n g u l ari ar i t y (Feature Axis to Datum Axis) NOTE: Featur eature e axis must li e within wit hin t olerance zone cyli nder 0.3 A

NOTE NOTE:: Toleranc e applies to featur feature e at RFS RFS

A


0.3 Circular Tolerance Zone 45 o

Datum Axis A The tole tol erance zone zone in this thi s example example is defined by a cylind cyl inde er equal to th e length o f th e feature, feature, orie ori ented at the specifi ed angle to the datum r eference axis.

Angularity is the condition condition of the feature axis at a specified angle (other than 90 degrees) to the datum reference axis, within the specified tolerance zone.

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An A n g u l ari ar i t y (Feature Axis to Datum Axis) NOTE: Featur eature e axis must li e within wit hin t olerance zone cyli nder 0.3 A

NOTE NOTE:: Toleranc e applies to featur feature e at RFS RFS

A


0.3 Circular Tolerance Zone 45 o

Datum Axis A The tole tol erance zone zone in this thi s example example is defined by a cylind cyl inde er equal to th e length o f th e feature, feature, orie ori ented at the specifi ed angle to the datum r eference axis.

Angularity is the condition condition of the feature axis at a specified angle (other than 90 degrees) to the datum reference axis, within the specified tolerance zone.

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Perpendicularity (Feature Surface to Datum Surface) 0.3 A

A 0.3 Wide Tolerance Zone

A


The tolera tol erance nce zone in th is exampl example e is defined by t wo parallel planes planes ori ented ented perpendicul ar to t o th e datum datum reference reference plane.

A

Perpendicularity is the condition of the planar feature surface at a right angle to the datum reference plane, within the specified tolerance zone.

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Perpendicularity (Feature Axis to Datum Surface) 0.3 Diameter Tolerance Zone

NOTE: Tolerance applies to feature at RFS RFS 0.3 Circular Tolerance Zone

C 0.3 Circular Tolerance Zone 0.3 C

The tolera tol erance nce zone in th is exampl example e is defined by a cylind cyl inder er equal equal to th e length o f the featur feature, e, orie ori ented perpendicu lar to the datum reference plane.

Perpendicularity is the condition of the feature axis at a right angle to the datum reference plane, within the specified tolerance zone.

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Perpendicularity (Feature Axis to Datum Axis) NOTE: Tolerance applies to feature featur e at at RFS RFS

A

0.3 A


Datum Axis A The tole tol erance zone zone in this thi s example is defined by two parallel parallel planes oriented ori ented perpendicular perpendicu lar to t he datum datum reference reference axis. axis.

Perpendicularity is the condition of the feature axis at a right angle to the datum reference axis, within the specified tolerance zone.

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Parallelism (Feature Surface to Datum Surface) 0.3 A

25 +/-0.5

A 0.3 Wide Tolerance Zone

25.5 max


24.5 min

A

The tolerance to lerance zon zone e in thi t his s exampl example e is defin defined ed by two parallel parallel planes orie ori ented parallel parallel to t he datum datum reference plane. p lane.

A

Parallelism is the condition of the planar feature surface equidistant at all points from the datum reference plane, within the specified tolerance zone.

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Parallelism (Feature Axis to Datum Surface) NOTE NOTE:: The specifi speci fied ed tolerance to lerance does not apply to the orientation orientation of t he fea feature axis axis in this direction

NOTE: Tolerance applies to feature at RFS RFS


0.3 A

A

The tolerance to lerance zon zone e in thi t his s exampl exampl e is defin defin ed by two parallel parallel planes oriente ori ented d parallel parallel to t he datum datum reference plane. p lane.

A

Parallelism is the condition of the feature axis equidistant along its length from the datum reference plane, within the specified tolerance zone.

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Parallelism (Feature Axis to Datum Surfaces) 0.3 Circular Tolerance Zone

B

NOTE: Tolerance applies to feature at RFS RFS 0.3 Circular Tolerance Zone

0.3 Circular Tolerance Zone 0.3 A B

B

A

The tolera tol erance nce zone in th is exampl example e is defined by a cylin der equal equal to t he length of t he featur feature, e, orie ori ented parallel to the da d atum reference reference planes. planes.

A

Parallelism is the condition of the feature axis equidistant along its length from the two datum reference planes, within the specified tolerance zone.

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Parallelism (Feature Axis to Datum Axis) The tolera tol erance nce zone in t his exampl example e is defined by a cylin der equal equal to t he length o f the t he feature, feature, orie ori ented parallel parallel t o t he datum r eference axis axis.. NOTE: Tolerance applies to feature featur e at at RFS RFS 0.1 Circular Tolerance Zone

0.1 A 0.1 A

A


Datum Axis A

Parallelism is the condition of the feature axis equidistant along its length from the datum reference axis, within the specified tolerance zone.

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Tolerances o f Runout Circular Runout (ASME Y14.5M-1994, 6.7.1.2.1)

Total Total Runout (ASME Y14.5M-1994 ,6.7.1.2.2)

Runout Characteristics are always related to datum

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Feature tu res s App Ap p l ica ic able bl e to Runou un outt Tole ol eranc rancin ing g Internal Internal surf s urface aces s constru cted around around a datum axis

External s urface urf aces s constr ucted around around a datum axis Datum axis (established from datum datum feature feature

Datum feature

An A n g l ed s u r f aces ac es constr ucted around around a datum datum axis

Surfaces constructed perpendicular to a datum axis

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Circu ir cula larr Runou un outt Total Tolerance

Maximum

Circular Circular runout runout can only be applied applied on an RFS basis and cannot be modified to MMC or LMC.

Minimum

Full Indicator Movement Maximum Reading

+

Minimum Reading 0

-

Measuring position #1 (circular element #1)

Full Part Rotation

Measuring position #2 (circular element #2)

When measuring circular circular runout, the indicator must be reset to zero at each measuring measuring position along the feature surface. Each individual circular element of the surface is independently allowed the full specified tolerance. tolerance. In this example, circular circular runout can be used to detect 2dimensional wobble (orientation) and waviness (form), but not 3-dimensional characteristics such as surface profile (overall form) or surface wobble (overall orientation).

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Circu ir cula larr Run Runou outt (Angled Surface to Datum Axis) 0.75 A A

50 +/-0.25

50

o

+/- 2

o

As A s Sho Sh o w n on Drawin rawing g Mea Means This: hi s: Allowable indicator indicator reading = 0.75 max. Full Indicator Movement

(

) -

0

+

The tolerance zone zone for any ind ivi dual circ ular element element is equal to the total allo wable movement of a dial indicator fixed fixed in a positi on normal to th e true geometric s hape of the feature surface when the part is rotated 360 360 degrees degrees about th e datum axis. The The tolerance lim it i s applied ind ependently ependently to each each indi vidual measuring measuring position along the feature surface. Collet Collet or Chuc Chuck k

When measuring circular runout, the indicator must be reset when repositioned along the feature surface.

Datum axis A

360 o Part Rotation

Single circular element

NOTE: Circula ircularr runout runout in this this exa example mple only cont rols th e 2-dimensi 2-dimensi onal circul ar elements elements (circularity and coaxiality) of t he angled angled feature surface not the entire angled angled feature feature surface

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Circu ir cula larr Run Runou outt (Surface Perpendicular to Datum Axis) 0.75 A A

50 +/-0.25

As A s Sho Sh o w n on Drawin rawing g Mea Means This: hi s:

Single circular element

The tolerance zone zone for any in divi dual cir cular element element is equal to t he total allowable movement of a dial indicator fixed in a position normal to th e true geometric shape of the feature surface when the part is rotated 360 360 degrees degrees about t he datum axis. The The tolerance limit i s applied in dependently dependently to each each ind ividual measuring measuring p osition along the feature surface. -

360 o Part Rotation

0

+


Allowable indicator indicator reading = 0.75 max.

Datum axis A NOTE: Circula ircularr runout runout in this this exa example mple will only control variation variation in th e 2-dime 2-dimensional nsional circu lar elements elements of the planar surface (wobb (wobb le and waviness) waviness) not the entire feature feature surface

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Circu ir cula larr Run Runou outt (Surface Coaxial to Datum Axis) 0.75 A

A

50 +/-0.25


The tolerance zone zone for any indi vidu al circu lar element element is equal to the total allowable movement of a dial indic ator fixed in a posi tion norm al to the true geometric geometric sh ape of the feature feature surface when the part i s ro tated tated 360 degrees degrees about the datum axis. The The tolerance limit i s applied in dependently dependently to each indi vid ual measuring measuring pos iti on along the feature feature surface. +


0

-

When measuring circular runout, the indicator indicator must be reset when repositioned along the feature surface.

Single circular element 360 o Part Rotation

Datum axis A

NOTE: Circula ircularr runout runout in this this exa example mple will only co ntrol variation variation in th e 22-dimensional circu lar elements elements of t he surface (circularity and coaxiality) coaxiality) not the entire feature feature surface surface

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Circu ir cula larr Run Runou outt (Surface Coaxial to Datum Axis) 0.75 A-B

A

B


The tolerance zone zone for any indi vidu al circu lar element element is equal to the total allowable movement of a dial indic ator fixed in a posi tion norm al to the true geometric geometric sh ape of the feature feature surface when the part i s ro tated tated 360 degrees degrees about the datum axis. The The tolerance limit i s applied in dependently dependently to each indi vid ual measuring measuring pos iti on along the feature feature surface. +


Machine center

0

-

When measuring circular runout, the indicator indicator must be reset when repositioned along the feature surface.

Single circular element Datum axis A-B

360 o Part Rotation

Machine center NOTE: Circula ircularr runout runout in this this exa example mple will only co ntrol variation variation in th e 22-dimensional circu lar elements elements of t he surface (circularity and coaxiality) coaxiality) not the entire feature feature surface surface

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Circu ir cula larr Run Runou outt (Surface Related to Datum Surface and Axis) A

B

0.75 A B 50 +/-0.25

As A s Sho Sh o w n on Drawin rawing g The tolerance zone zone for any in divi dual circ ular element element is equal to the total allowable movement movement of a dial ind icator fi xed in a positi on nor mal to the true geometric shape of the feature feature surf ace when the part is located against against the datum sur face and and rotated r otated 360 degrees about t he datum axi s. The The tolerance limi t is applied independently to each each ind ivid ual measuri measuri ng pos iti on along t he feature feature surface. surface.

Mea Means This: hi s:

Single circular element Allowable indicator indicator reading = 0.75 max.

Stop collar 360 o Part Rotation

+

0

-

Collet Collet or Chuck Chuck

Datum axis B


Datum plane A

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To t al Ru Ru nou no u t Total Tolerance

Maximum

Total runout runout can only only be applied applied on an RFS basis and cannot be modified to MMC or LMC.

Minimum

Full Indicator Movement Maximum Reading

Minimum Reading

+

0

-

Indicator Path

Full Part Rotation

+

0

-

When measuring total runout, the indicator is moved in a straight line along the feature surface while the part is rotated about the datum axis. It is also acceptable acceptable to measure total runout by evaluating an appropriate appropriate number of individual circular circular elements along the surface while the part part is rotated about the datum axis. Because the tolerance value is applied to the entire surface, the indicator must not be reset to zero when moved to each measuring position. In this example, total runout can be used to measure measure surface profile (overall (overall form) and surface surface wobble (overall orientation).

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Tota ot al Runou un outt (Angled Surface to Datum Axis) 0.75 A A

50 +/-0.25

50

o

+/- 2

o

As A s Sho Sh o w n on Drawin rawing g Mea Means This: hi s: When measuring total runout, the indicator indicator must must not be reset when when repositioned along the feature surface.

-

0

+

0

+

The tolerance zone zone for the entire angled angled surf ace is equal to the total allowable movement of a dial indicator posit ioned normal to the true geometric geometric shape of th e feature feature surf ace when when t he part is rotated about about the datum axis axis and the ind icator is moved along t he entir entir e length length of th e feature feature surface. Allowable indicator indicator reading reading = 0.75 max. (applies to the entire feature surface)

Collet Collet or Chuck Chuck

Full Part Rotation

Datum axis A

NOTE: TE: Unlike circular runout, the use of total runout will provide 3-dimensional 3-dimensional composite control of the cumulative variations of circularity, coaxiality, angularity, taper and and pr ofil e of the angled angled su rface

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Tota ot al Runou un outt (Surface Perpendicular to Datum Axis) 0.75 A

10 35

50 +/-0.25

A

Mea Means This: hi s:

10 35 Full Part Rotation

As A s Sho Sh o w n on Drawing

The tolerance zone zone for t he porti on o f th e feature feature surface ind icated is equal to the total allo allo wable movement movement of a dial ind icator posi tio ned normal to the true geometric geometric shape of the feature feature surf ace when the part is rotated about th e datum axis and the indicator is mo ved alon alon g the portio n of the feature feature surface within the area area describ describ ed by the basic basic di mensions .

-

0

-

0

+ +

When measuring total runout, the indicator must not be reset when repositioned repositioned along the feature surface.

Allowable indicator indicator reading = 0.75 max. (applies to portion of feature surface indicated)

Datum axis A NOTE: TE: The use of total runout in this example example will pro vide composite control of t he cumulative cumulative variatio variatio ns of perpendicu larity (wobbl e) and flatness (concavity or c onvexity) of th e feature feature surface.

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Tolerances o f Profile Profile Profil e of a Line (ASME Y14.5M-1994, 6.5.2b)

Profile Profil e of a Surf Surface ace (ASME Y14.5M-1994, 6.5.2a)

Profile Characteristics may be or may not be related to datum

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Prof ro f ile il e of a Line Li ne 20 X 20 A1

B 20 X 20 A3

20 X 20 A2

C

1 A B C

17 +/+/- 1 A

1 Wide Profile Tolerance Zone

2 Wide Size Tolerance Zone 18 Max 16 Min.

The profile tolerance zone in this example is defined by two parallel lines oriented with respect to the datum reference frame. The profile tolerance zone is free to float within the larger size tolerance and applies only to the form and orientation of any individual line element along the entire surface. Profile of a Line is a two-dimensional tolerance that can be applied to a part feature in situations where the control of the entire feature surface as a single entity is not required or desired. The tolerance applies to the line element of the surface at each individual cross section indicated on the drawing.

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Pr o f i l e o f a Su r f ac e 20 X 20 A1

B 20 X 20 A3

20 X 20 A2

2 A B C

C

23.5

A

2 Wide Tolerance Zone Size, Form and Orientation

23.5

Nominal Location

The profile tolerance zone in this example is defined by two parallel planes oriented with respect to the datum reference frame. The profile tolerance zone is located and aligned in a way that enables the part surface to vary equally about the true profile of the feature.

Profile of a Surface is a three-dimensional tolerance that can be applied to a part feature in situations where the control c ontrol of the entire feature surface as a single entity is desired. The tolerance applies to the entire surface and can be used to control size, location, form and/or orientation of a feature surface.

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Pr o f i l e o f a Su r f ac e (Bilateral Tolerance) 20 X 20 A1

B 20 X 20 A3

20 X 20 A2

1 A B C

C 50

1 Wide Total Tolerance Zone

B

0.5 Inboard 0.5 Outboard

C

50

Nominal Location

The tolerance zone in this example is defined by two parallel planes oriented with respect to the datum reference frame. The profile tolerance zone is located and aligned in a way that enables the part surface to vary equally about the true profile of the trim. Profile of a Surface when applied to trim edges of sheet metal parts will control the location, form and orientation of the entire trimmed surface. When a bilateral bilateral value is specified, specified, the tolerance zone allows the trim edge variation variation and/or locationa locationall error to be on both sides of the true profile. profile. The tolerance tolerance applies to the entire edge surface.

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Pr o f i l e o f a Su r f ac e (Unilateral Tolerance) 20 X 20 A1

B 20 X 20 A3

20 X 20 A2

0.5 A B C

C 50

0.5 Wide Total Tolerance Zone

B

C

50

Nominal Location

The tolerance zone in this example is defined by two parallel planes oriented with respect to the datum reference frame. The profile tolerance zone is located and aligned in a way that allows the trim surface to vary from the true profile only in the inboard direction. Profile of a Surface when applied to trim edges of sheet metal parts will control the location, form and orientation of the entire trimmed surface. When a unilateral value is specified, the tolerance zone limits the trim edge variation and/or locationa locationall error to one side of the true profile. profile. The tolerance tolerance applies applies to the entire edge surface.

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Pr o f i l e o f a Su r f ac e (Unequal Bilateral Tolerance) 20 X 20 A1

B 20 X 20 A3

20 X 20 A2

0.5 1.2 A B C C 50

1.2 Wide Total Tolerance Zone

B

0.5 Inboard 0.7 Outboard

C

50

Nominal Location

The tolerance zone in this example is defined by two parallel planes oriented with respect to the datum reference frame. The profile tolerance zone is located and aligned in a way that enables the part surface to vary from the the true profile profile more in one direction direction (outboard) (outboard) than in the other (inboard). Profile of a Surface when applied to trim edges of sheet metal parts will control the location, form and orientation of the entire trimmed surface. Typically when unequal values are specified, the tolerance zone will represent the actual measured measured trim edge variation variation and/or locational locational error. The tolerance tolerance applies applies to the entire edge surface.

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Pr o f i l e o f a Su r f ac e

0.5 A 0.1

Location & Orientation Form Only

25

A 0.1 Wide Tolerance Zone 25.25

24.75

A

Compo om posi site te Profi ro file le of Two Two Coplana op lanarr Surface ur faces s w/ w /o Orienta Orient ation ti on Refineme fi nement nt

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Pr o f i l e o f a Su r f ac e 0.5 A 0.1 A

Location Form & Orientation

25

A 0.1 Wide Tolerance Zone 25.25

A


24.75

A

Compo om posi site te Profi ro file le of Two Coplana op lanarr Surf ur f aces Wi Wi th Or ienta ient ation ti on Refi Refineme nement nt

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Tolerances o f Location True Position Positi on (ASME Y14.5M-1994, 5.2)

Symmetry (ASME Y14.5M-1994, 5.13)

Concentricity (ASME Y14.5M-1994, 5.12)

Profile Characteristics mostly requires datum

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Coordinate oordinate vs Geometric ometric Tole ol eranc rancin ing g Method th ods s 8.5 8.5 +/+/- 0.1 0.1

8.5 8.5 +/+/- 0.1 0.1

1.4 A B C Circular Tolerance Zone

Rectangular Tolerance Zone 10.2 10.25 5 +/+/- 0.5 0.5

10.25 B

10.2 10.25 5 +/+/- 0.5 0.5

10.25

C

A

Coordin oor dina ate Dimensionin imensio ning g

Geometric Dimensionin imensio ning g

+/- 0.5 1.4 +/- 0.5

Rec t an g u l ar To l er an c e Zo n e

57% 57% Larger Lar ger Tole ol erance ranc e Zon Zone e

Ci r c u l ar To l er an c e Zo n e

Circular Tolerance Zone

Rectang Rectang ular ul ar Toleranc Toleranc e Zone Zone

Increa nc reased sed Eff Effe ectiv ct ive e Tolerance

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Posit os itio ional nal Tol Tole erance Verifi ri ficatio cation n (Applies when a circular tolerance is indicated)

X Z Feature axis actual location (measured)

Y

Positional tolerance zone cylinder Actual feature boundary

Feature axis true position (designed)

Formu or mula la to determ determine ine the th e act actual ual radial radial posit pos ition ion of a fea feature tu re using usi ng me m easure sur ed coor co ordi dinate nate values (RF (RFS) Z= Z

X2 +

Y2

positional tolerance /2

Z = tota totall rad radia iall dev deviiatio ation n X2 = “X” measured deviation Y2 = “Y” measured deviation

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BiBi -dire di rect ctio iona nall Tru True e Posit os itio ion n Recta ct angul ng ula ar Coo Coord rdin ina at e Method th od 1.5 A B C

2X

2X

0.5 A B C

C

A

10

B 10


35

2X

6 +/-0.25

Mea Means This: hi s: True Position Related to Datum Reference Frame


C

10

B 10

35


Each axis must lie within the 1.5 X 0.5 rectangular tolerance zone basically located to the datum reference frame

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BiBi -dire di rect ctio iona nall Tru True e Posit os itio ion n Multi ul tipl ple e Si ngleng le-S Segme gm ent Method th od 2X

6 +/-0.25

1.5 A B C 0.5 A B

C

A

10

B 10


35

Mea Means This: hi s: True Position Related to Datum Reference Frame


C

10

B 10

35


Each axis must lie within the 1.5 X 0.5 rectangular tolerance zone basically located to the datum reference frame

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BiBi -dire di rect ctio iona nall Tru True e Posit os itio ion n Noncyln onc ylndri drica call Feature tur es (Boundary Bou ndary Concept) 2X 13 +/-0.25 1.5 M A B C BOUNDARY

2X 6 +/-0.25 0.5 M A B C BOUNDARY

C

A

10

B 10

35


5.75 MMC length of slot -0.50 Position tolerance 5.25 maximum boundary

Mea Means This: hi s: Both holes must be within the size limits and no portion of their surfaces may lie within the area described by the 11.25 x 5.25 maximum boundaries when the part is positioned with respect to the datum reference frame. The boundary concept can only be applied on an MMC basis.

12.75 MMC width of slot -1.50 Position tolerance 11.25 Maximum boundary

True position boundary related to datum reference frame

C 90 o 10 10

35

B

A

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Location (Concentricity) Dat u m Feat u r es at RFS 6.35 6.35 +/+/- 0.05 0.05 0.5 A

A

15.95 15.90

As A s Sho Sh o w n o n Draw Dr awii n g Mea Means This: hi s:

Axis of Datum Feature A

0.5 Coaxial Tolerance Zone

Derived Median Points of Diametrically Opposed Elements Within the limits of size and regardless of feature size, all median points of diametrically opposed elements must lie within a 0.5 cylindrical tolerance zone. The axis of the tolerance zone coincides with the axis of datum feature A. Concentricity can only be applied on an RFS basis.

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Location (Symmetry) Dat u m Feat u r es at RFS 6.35 6.35 +/+/- 0.05 0.05 0.5 A

A

15.95 15.90

As A s Sho Sh o w n o n Draw Dr awii n g Mea Means This: hi s:

Center Plane of Datum Feature A


Derived Median Points Within the limits of size and regardless of feature size, all median points of opposed elements must lie between two parallel planes equally disposed about datum plane A, 0.5 apart. Symmetry can only be applied on an RFS basis.

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Fixed and Floating Fastener Exercises

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Floating Fasteners In applications where two or more mating details are assembled, and all parts have clearance holes for the fasteners, the floating fastener fastener f ormula shown below can be used to calculate the appropriate hole sizes or positional tolerance requirements to ensure assembly. The formula will provide a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance

2x M10 X 1.5 (Reference)

General Equation Applies to Each Part Individually

H=F+T or T=H-F

A

H= Min. diameter of clea cl earance rance hole ho le F= Maximum diameter of fastener T= Posi Positio tional nal tolerance t olerance diameter diameter

B

2x

+/- 0.25 0.25 10.50 +/?.? M

Calculate Calculate Required Required Positional Tolerance

T=H-F H = Minimum Hole Size = F = Max. Fastener Size =

T = 10.25 -10 T = ______

A 2x

Calculate Nominal Size

??.?? 0.5

+/+/- 0.25 0.25

M

remember: the size tolerance must be added to th e calculated MMC MMC hole size to obtain the correct nom inal value. value.

H = F +T F = Max. Fastener Size = T = Positional Tolerance =

B

10.25 10

H = 10 + 0.50 H = ______

10 0.50

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Floating Fasteners In applications where two or more mating details are assembled, and all parts have clearance holes for the fasteners, the floating fastener fastener f ormula shown below can be used to calculate the appropriate hole sizes or positional tolerance requirements to ensure assembly. The formula will provide a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance

2x M10 X 1.5 (Reference)

General Equation Applies to Each Part Individually

H=F+T or T=H-F

A


B

2x

+/- 0.25 0.25 10.50 +/0.25 M

Calculate Calculate Required Required Positional Tolerance

T=H-F H = Minimum Hole Size = F = Max. Fastener Size =

T = 10.25 -10 T = 0.25

A 2x


10.25 10

10.75 0.5

+/+/- 0.25 0.25

M


H = F +T F = Max. Fastener Size = T = Positional Tolerance =

B

H= H=

10 + .5 10.5 Minimum

REMEM EMEMBER BER!!! !!! All Calcu Calculation lations s Apply App ly at MM MMC

10 0.5

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Fixed Fasteners In fixed fastener applications where two mating details have equal equa l positional tolerances, the fixed fastener formula shown below can be used to calculate the appropriate minimum clearance hole size and/or positional tolerance required to ensure assembly. The formula provides a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance. (Note that in this example the positional tolerances indicated are the same for both parts.)

APPLIES WHEN WHEN A PROJECTED TOLERANCE ZONE ZONE IS USED 2x M10 X 1.5 (Reference)

General General Equati on Used When When Positio nal Tolerances Tolerances Are Equal

H=F+2T or T=(H-F)/2

A

10


B

Calculate Calculate Required Required Clearance Hole Size.

2x

??.?? 0.8

+/+/- 0.25 0.25

M

A

0.8

M P

H = F + 2T Nominal Size (MMC For Calculations)

2X M10 X 1.5 10

remember: remember: the si ze tolerance must be added added to t he calculated calculated MMC MMC size to obtain t he correct nomin al value. value.

F = Max. Fastener Size = T = Positional Tolerance =

H = 10.00 + 2(0.8) H = _____ B

10.00 0.80

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H=F+2T or T=(H-F)/2

A

10


B


2x

11.85 0.8

+/+/- 0.25 0.25

M

A

0.8

M P


2X M10 X 1.5 10



10.00 0.80

H = 10.00 + 2(0.8) H = 11.60 Minimum B


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H=F+2T or T=(H-F)/2

A

10


B


2x

11.85 0.8

+/+/- 0.25 0.25

M

A


2X M10 X 1.5 0.8 M P 10



H = 10 + 2(0.8) H = 11.6 Minimum B


10 0.8

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Fixed Fasteners In applications where two mating details are assembled, and one part has restrained fasteners, the fixed fastener formula shown below can be used to calculate appropriate hole sizes and/or positional tolerances required to ensure assembly. The formula will provide a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance. (Note: in this example the resultant positional tolerance is applied to both parts equally.)


General General Equati on Used When When Positio nal Tolerances Tolerances Are Equal 10

H=F+2T or T=(H-F)/2

A


B

2x

+/- 0.25 0.25 11.25 +/0.5 M

A

T = (H - F)/2 H = Minimum Hole Size = F = Max. Fastener Size =

2X M10 X 1.5

Nomin al Size (MMC For Calculations)

Calculate Calculate Required Required Position al Tolerance Tolerance . (Both Parts)

0.5

M P

10

T = (11 (11 - 10)/ 10)/2 2 T = 0.50

B REMEM EMEMBER BER!!! !!! All Calcu Calculation lations s Apply App ly at MM MMC

11 10

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Fixed Fasteners In fixed fastener applications where two mating details have unequal positional tolerances, the fixed fastener formula shown below can be used to calculate the appropriate minimum clearance hole size and/or positional tolerances required to ensure assembly. The formula provides a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance. (Note that in this example the positional tolerances indicated are not equal.)

APPLIES WHEN WHEN A PROJECTED TOLERANCE ZONE ZONE IS USED 2x M10 X 1.5

General General Equation Equati on Used When When Positio nal Tolerances Tolerances Ar e Not Not Equal Equal

(Reference)

10

H=F+(T1 + T2)

A

H = Min. diameter of clea cl earance rance hol e F = Maximum diameter of fastener T1= Posit ional io nal tol erance (Part (Part A) T2= Positional Positi onal tol erance erance (Part (Part B)

B


2x

+/- 0.25 0.25 ??.?? +/0.5 M

A 2X M10 X 1.5 1 M P 10



H=F+(T1 + T2) F = Max. Fastener Size T1 = Positional Tol. (A) T2 = Positional Tol. (B)

H = 10+ (0.5 + 1) H = ____ B

= = =

10 0.50 1

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Fixed Fasteners In fixed fastener applications where two mating details have unequal positional tolerances, the fixed fastener formula shown below can be used to calculate the appropriate minimum clearance hole size and/or positional tolerances required to ensure assembly. The formula provides a “zero-interference” fit when the features are at MMC and at their extreme of positional tolerance. (Note that in this example the positional tolerances indicated are not equal.)

APPLIES WHEN WHEN A PROJECTED TOLERANCE ZONE ZONE IS USED 2x M10 X 1.5

General General Equation Equati on Used When When Positio nal Tolerances Tolerances Ar e Not Not Equal Equal

(Reference)

H= F+(T1 + T2)

A

10

H = Min. diameter of clea cl earance rance hol e F = Maximum diameter of fastener T1= Posit ional io nal tol erance (Part (Part A) T2= Positional Positi onal tol erance erance (Part (Part B)

B


2x

+/- 0.25 0.25 11.75 +/0.5 M

A 2X M10 X 1.5 1 M P 10


remember: remember: the size tolerance must b e added to t he calculated MMC MMC hole size to obtain the correct nominal value.

H=F+(T1 + T2) F = Max. Fastener Size T1 = Positional Tol. (A) T2 = Positional Tol. (B)

= = =

H = 10 + (0.5 + 1) H = 11.5 Minimum B REMEM EMEMBER BER!!! !!! All Calcu Calculation lations s Apply App ly at MM MMC

10 0.5 1

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Fixed Fasteners

In applications where a proj ected ected tol erance erance zone zone is no t indicated, it is necessary to select a positional tolerance and minimum clearance hole size combination that will allow for any out-of-squareness of the feature containing the fastener. The modified fixed fastener formula shown below can be used to calculate the appropriate minimum clearance hole size required to ensure assembly. The formula provides a “zero-interference” fit when the features are at MMC and at the extreme positional tolerance.

APPLIES WHEN A PROJECTED TOLERANCE ZONE IS NOT USED H

F

P

A

D

B


2x

H= Min. diameter of clearance hole F= Maximum diameter of pin T1= Positional tolerance (Part A) T2= Positional tolerance (Part B) D= Min. depth of pin (Part A) P= Maximum projection of pin

??.?? +/-0.25 0.5 M

A 2x

remember: remember: the size tolerance must be added to t he calculated MMC MMC hole size to obtain the correct nominal value.

H= F + T1 + T2 (1+(2P/D))

10.05 +/-0.05 0.5 M

F = Max. pin size T1 = Positional Tol. (A) T2 = Positional Tol. (B) = Min. pin depth = Max. pin projection

=

10 = 0.5 = 0.5 D = 20. P = 15

B

H = 10.00 + 0.5 + 0.5(1 + 2(15/20)) H= __________

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Fixed Fasteners

In applications where a proj ected ected tol erance erance zone zone is no t indicated, it is necessary to select a positional tolerance and minimum clearance hole size combination that will allow for any out-of-squareness of the feature containing the fastener. The modified fixed fastener formula shown below can be used to calculate the appropriate minimum clearance hole size required to ensure assembly. The formula provides a “zero-interference” fit when the features are at MMC and at the extreme positional tolerance.

APPLIES WHEN A PROJECTED TOLERANCE ZONE IS NOT USED H

F

P

A

D

B


2x

H= Min. diameter of clearance hole F= Maximum diameter of pin T1= Positional tolerance (Part A) T2= Positional tolerance (Part B) D= Min. depth of pin (Part A) P= Maximum projection of pin

12 +/-0.25 0.5 M

A 2x

H= F + T1 + T2 (1+(2P/D))

remember: remember: the size tolerance must be added to t he calculated MMC MMC hole size to obtain the correct nominal value.

H= F + T1 + T2 (1+(2P/D))

10.05 +/-0.05 0.5 M

F = Max. pin size T1 = Positional tol. (A) T2 = Positional tol. (B) = Min. pin depth = Max. pin projection

= 10 = 0.5 = 0.5 D = 20 P = 15

B

H = 10 + 0.5 + 0.5(1 + 2(15/20)) H= 11.75 Minimum


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Notes

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Notes

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Notes

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manufacturing lecture

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