Unsolved Problems

Generator lines

Straightness

Generator LineStaightness

section lineof section plane

ISO 2692CZ common zone SZ separate zones

Acc. To

Principle of independency

CZ superfluous

CZ superfluous

CZ ?

szb)

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 functionsCoincides with former practiceCoinsides 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 / 3in order to avoidsteps 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 form0,0015 apart (width = 0,003)

location arbitrary

ISO 1660

Best Fit Reference