ISO GD&T vs. ASME GD&T 8

[pmarc]

What do you think about discussing more in details about differences between ISO and ASME GD&T? What are the most important discrepancies between the two in your opinion?

 

[CheckerHater]

AK,

My bad :-(

Jim,

There are heated discussions happening about what cones are good for.
Will be glad to see more of you on this forum

 

[MechNorth]

CH, let me know when & where if I miss the posts.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[KENAT]

OK, where does it say that clause only applies to vent holes? (Plus vent holes are an over used example for features that don't matter in my opinion - my vent holes always seem to be close enough to each other or to other features that their size & location matters more than one might initially expect)

Iso 2768-1 6. Unless otherwise stated, workpieces exceeding the general tolerance shall not lead to automatic rejection provided that the ability of the workpiece to function is not impaired (see clause A.4).

Iso 2768-1 A.4 The tolerance the function allows is often greater than the general tolerance. The function of the part is, therefore, not always impaired when the general tolerance is (occasionally) exceeded at any feature of the workpiece. Exceeding the general tolerance should lead to a rejection of the workpiece only if the function is impaired.

I get the idea that the general idea is that the 'general tols' are meant to be so 'loose' that they should easily be met. However, I don't fully buy into what it says in A.3 about reducing the need to do detailed tolerance calculations. I don't see how it helps guarantee parts will fit or similar which is when you do detailed tol calcs typically.

Perhaps, if you're using the spec properly, any directly functional dimensions are actually fully specified on the drawings, while only those that are effectively in 'free space' or similar fall under the 2768.

However, I've never really seen it used this way - though as I've conceded before, in this extent it's comparable to block tols being misused.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[CheckerHater]

OK, where does it say that "any part 'A' would assemble to any part 'B'" based on general tolerances all alone?