First Part Of

CALLOUT MEANS THIS: Datum plane A

Pattern-locating tolerance zone framework (PLTZF). 01 tolerance cylinders basically located and oriented relative to each other and to the specified datum reference frame.

0 0.5 tolerances zone cylinders

FIG. 5-22 COMPOSITE POSITIONAL TOLERANCING OF A CIRCULAR PATTERN OF FEATURES (CONTD)

ADDITIONALLY, SECOND PART OF CALLOUT MEANS THIS:

Positional Tolerance

One possible location and orientation of feature-relating tolerance zone framework (FRTZF) relative to pattern-locating tolerance zone framework (PLTZF).

FIG. &-22 COMPOSITE POSITIONAL TOLERANCING OF A CIRCULAR PATTERN OF FEATURES (CONTD)

Geometric Tolerance Hole
FIG. 5-22 COMPOSITE POSITIONAL TOLERANCING OF A CIRCULAR PATTERN OF FEATURES (CONT'D)

5.4.1.6 Radial Hola Pattern. Figure 5-24 shows an example of a radial hole pattern where the plane of the PLTZF is located from a datum face by a basic dimension. Where datum references are not specified in the lower segment of a composite feature control frame, the FRTZF is free to be located and oriented (shift and/or tilt) as governed by the tolerance zones of the PLTZF. The same explanation given in para. 5.4.1 also applies to Fig. 5-24. With datum plane A referenced in the lower segment of the composite feature control frame, the tolerance zones of the FRTZF (as a group) are parallel to datum plane A and may be displaced as governed by the tolerance zones of the PLTZF. Figure 5-26 shows two single-segment feature control frames. These are used where it is desired to specify a need for a coaxi-ality relationship between the FRTZF and the PLTZF. A secondary datum reference is shown in the lower feature control frame. Figure 5-26(c) shows that the tolerance zones of the FRTZF are parallel to datum plane A and concentric about datum axis B. While remaining parallel and concentric, the FRTZF may be displaced rotationally, as governed by the tolerance cylinders of the PLTZF. The axes of the features in the actual feature pattern may be displaced, individually or in concert, within the boundaries of the smaller tolerance cylinders. Portions of the smaller tolerance zones located outside the larger tolerance zones are not usable, since the actual feature axes must reside within the boundaries of both zones. Where two single-segment feature control frames are used and it is desired to avoid a reorientation of the workpiece in mid-operation, the same datums in the same order of precedence are specified to apply in the upper and lower feature control frames.

5.4.1.7 Where Radial Location is Important. The control shown in Figs. 5-25 and 5-27 may be specified where radial orientation is important, yet the design permits a feature-relating tolerance zone to be displaced within the bounds governed by a pattern-locating tolerance zone, while held parallel and perpendicular to the three mutually perpendicular planes of the datum reference frame.

5.4.1.6 Difference Between Composite Positions! Tolerance and Two Single-Segment Feature Control Frames. Figure 5-29 explains the relationships of the FRTZF to the PLTZF established by a two-segment feature control frame having a single positional tolerance symbol (composite positional tolerance). Two different part configurations are shown for comparison. In contrast. Fig. 5-30 shows the relationships established by two single-segment feature control frames.

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  • fiyori
    How to tolerance hole patterns?
    8 years ago

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