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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
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