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Chapter 14: A. Geometric Dimensioning and Tolerancing (GD&T) 147
Table 14.1 Other feature control symbols.
Symbol
F
L
M
P
S
T
U
Modifier
Free state
Least material condition
Maximum material condition
Projected tolerance zone
Regardless of feature size
Tangent plane
Unilateral
0.001
Figure 14.11 Example of symbols on an engineering drawing.
3. POSITION AND BONUS TOLERANCES
Part III.A.3
Calculate these from various drawings.
(Analysis)
Body of Knowledge III.A.3
Bonus tolerance is an additional tolerance that is used for geometric control. Whenever
a geometric tolerance is applied to a feature of size, and it contains a maximum
material condition (MMC) or least material condition (LMC) modifier in the tolerance
portion of the feature control frame, a bonus tolerance is permissible (Effective
Training 2008).
Tolerance of position control is a geometric tolerance that defines the location tolerance
of a feature of size from its true position (Effective Training 2008).
If a position is identified exactly on a drawing, the tolerance is applied at LMC,
MMC, regardless of feature size. If LMC or MMC is listed, we can calculate a
wider tolerance, or bonus, depending on the actual size of the measured feature.
When using the regardless of feature size approach we are not allowed to consider
bonus tolerance, and the center of the measured feature must lie within the tolerance
zone specified. For example, the symbols in Figure 14.11 on an engineering