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11 POSITIONAL TOLERANCE

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The true position of the hole is given by basic dimensionsand a 0.2 positional tolerance. (single feature)

16

12

10

RS

0.2 P R S 0.2 tol zone at

true position of

hole

P

Positional tolerance uses a feature control frame to specify the tolerance zone required to

accurately locate a feature or group of features such as center point(s), center axis, or the centerof a plane.

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Positional tolerance is applied to a group of holes locatedwith basic dimensions. (multiple features)

8.3

8.0

11

11

0.4 V W

4X 6.0

5.7

W

7 7V

11

11

0.4 V W

4X 6.0

5.7

W

7 7V

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The central axes of the holes are: at true position, atextreme position, and at extreme attitude.

**Remember(holes, shafts, pins):

The tolerance zone is described as a cylinder with diameter equal to the tolerance value andwith the length or height of the feature.

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The table shows the positional tolerance increasing as thehole moves away from MMC.

U

8.38.0

0.4 U V W

WV

Hole Pos Tol8.0 MMC 0.4

8.1 0.58.2 0.68.3 LMC 0.7

16

10

Bonus tolerance is the increase in positional tolerance as the hole moves away from MMC.

Holes Virtual Condition =

Parts MMC Positional Tolerance

VC = 8.0 0.4 = 7.6

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The red dots show the feature relating and the yellow thepattern location tolerance.

`

20

10

10

24

C

B

0.4 A B C

0.2 A

4X 14.314.0

Pattern locating tolFeature relating tol

20

24

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The center axes of the holes must meet the pattern locatingand feature relating tolerances simultaneously.

Position # 1 Alternate

position # 2

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A portion of the feature relating tolerance zone can spill over

beyond the pattern location tolerance zone.

Feature relatingboundary axis on edge

of pattern locatingboundary

Hole

Pattern locationboundary at trueposition

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If no datum is specified in the second row, the central axes of

the hole pattern has no orientation requirements.

0.4 A B C

0.2

Pattern of holesPattern tolerance intrue position

Feature tolerance

Datum C

Datum BDatum A

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A primary datum in the second row, requires the central axesto be perpendicular to the specified primary datum.

Datum C

Datum B

Datum A

0.4 A B C

0.2 A

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With two datums specified in the second row, the central

axis of the hole pattern must be perpendicular to the

primary datum and parallel to the secondary datum.

0.4 A B C

0.2 A B

Datum B