SECTION THICKNESS up to 1


lh" to 1" over l"


114" to 1 h"


Effect Of Dishing 14"


POSSIBLE DISH PER FACE OF CASTING not significant .002" .004" .006"


The amount of dishing allowed is in addition to the basic tolerance. Thus, on a block 1" ± .005" thick, the following would apply:


Dish / also refer to design section


The method of measuring flatness should be specified by the purchaser. It may vary from simple surface plate and feeler gage techniques up to full layout with equalization and dial indicators (premium).


Straightness


Mil Std. 8 states that "a tolerance covering the straightness of an axis is the diameter or width within which the axis must lie".


It is obvious from this that to correctly measure axial straightness of either a shaft, bar or plate, the tolerance zone, within which the axis or axial plane lies, must be measured.


Straightness Tolerance


Straightness may be a real problem with certain types of castings. A relatively thin, short part may bend while a long, heavy part may not. Experience tells the foundry that a given design may bend, but experience cannot say to what extent. As a rough guide, it may be said that a constant section will have an axial bow of .005" per inch. Ribs and gussets will inhibit warpage and will also hinder the mechanical straightening of whatever warpage has occurred.


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