Unsolved Problems

Generator lines Straightness

Generator Line Staightness section line of section plane

ISO 2692 CZ common zone SZ separate zones

Acc. To Principle of independency

CZ superfluous

CZ ?

sz b)

sz When a group of toleranced features is related to a datum or datum system containing a modifier M or L it is questionable whether CZ common zone (e.g. simultaneous gauging) or SZ separate zones (e.g. separate gauging) applies. Therefore in the future CZ or SZ shall always be indicated in these cases, see examples …

Alternative rule for ISO 2692: CZ applies (without indication of CZ) when positional tolerances are applied together with the maximum material requirement or the least material requirement, unless otherwise specified, e.g. by the symbol SZ. Advantages: Coincides with most functions Coincides with former practice Coinsides with ASME 14.5 Disadvantages: Violating the (fundamental) rule of Prindiple of independency Whatever the rule is, there is a need for an additional symbol SZ (= separate zones)

ISO 1660 Limitation of Steps

Profile tol. 0,003 / 3 in order to avoid steps and chatter marks What is the length 3 ? a)Length of a straight line (width of the window) b)Stretched length Proposal: a) = reference length (width of the window) Form of tol. zone limits = equidistant to theor. exact form 0,0015 apart (width = 0,003) location arbitrary

ISO 1660 Best Fit Reference