huangyhg

parallelism callout on a draft surface?
attached print is a forged part around 11 inches long, there is a flatness control on datum b, and on the other side there is a parallelism callout, it's easy to understand the parallelism wrt datum b from the plan view, but from the section view the two sides just looks like a v shape since there is a 5° draft angle all around, is it okay to use the parallelism callout here?
thanks
seasonlee

parallelism is a refinement - it appears to be used incorrectly here.

yes it is ok to use a parallelism tolerance here.
by the way, your numbering system on the datums is questionable with your concept on never duplicating a number. i saw datum b4 & b5 and wondered where b1 & b2 were??
dave d.
no it is not ok to use a parallelism tolerance here.
i suspect that the designer is attempting to keep the two drafted sides of the part uniform in width and straightness relative to one another. the control however does not pertain only to the edge of the surface and therefore does not make sense. [b] is two target points and cannot be used as a primary for the measurement of the opposite surface's parallelism. even if the parallelism was called out to [a|b] it would not make sense because the draft of the surface will be the minimum or given deviation for parallelism. profile would be the better choice.
paul

after reviewing paul's answer and the drawing again, i reluctantly agree with paul's answer. the draft angle nullifies parallelism.
dave d.
thanks for your inputs, dave and paul.
seasonlee
as shown i agree with paul & weavedreamer.
however, this is an application where 'line element' could perhaps be applied to achieve the desired end result.
i asked a similar question about dovetails a while back.
kenat,

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