Standard Clearances

[cadman1964]

I'm a designer for the deep draw stamping industry. One question going around is about clearance between two mating parts. We typically design in fit at assembly. The tooling is typically designed at .001" - .0015" clearance depending on the application. Our fit dia's can run anywhere from .25" up to 5" in dia.

To get to the question I'm trying to ask..

At what point do you increase your fit clearance. Some people around here are saying .001" per inch clearance, Others are saying .0005" per inch. We just built some tooling to where the fit dia's where over 6" dia. They designed in the normal clearance and now there working them in. (better than to much clearance) My experiencing saying .0005" per inch but i want to know what other brilliant engineering people think.

Solid Edge V20

 

[drawoh]

cadman1964,

Take the case that you have two parts located together by some datum features.

If you have a fixed feature on part[ ]A that must pass through a hole in part[ ]B, your positional tolerance must be one half the minimum clearance. If both both parts have a hole that a third feature must pass through, then the positional tolerances must be equal to the minimum clearance.

In other words, there is a relationship between your positional tolerances and your clearances. How accurately do you want to position stuff, and what maximum clearance can you tolerate?

JHG

 

[KENAT]

Sounds like an industry specific question more than a general dimensioning/tolerancing question. There might be other fora that are more likely to have others from your industry in them.

Like drawoh says, from a point of view of parts fitting together in an assy you can work it out on worst case fit or some statistical bases. However, I'm not sure this is what you're asking about.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

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

What is Engineering anyway: faq1088-1484

 

[cadman1964]

Yea youre most likely right, should maybe found a different forum for this. But anyways, i did find what i was looking for in the Machinerys Hand Book.

Solid Edge V20