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Re: [Phys-l] Sig figs

My experience in a aerospace research lab was somewhat different. I had a machinist assigned to me who I chatted with on a daily basis. He wanted to know what was important and what was not because precision took time and money. If a rough cut would work, he would do that, if I needed to a "thou" or better he would do that.


Joseph J. Bellina, Jr. Ph.D.
Emeritus Professor of Physics
Northern Indiana Science, Mathematics, and Engineering Collaborative

On Oct 17, 2010, at 4:38 AM, Michael Edmiston wrote:

I mentioned in an earlier post that it is helpful to let the machinists know
what you are up to. If they are told that one piece fits inside another
piece, and you would like 0.002" clearance between the two, then they will
make it that way. If you just give the dimensions, and they are doing +/-
0.001 work, you could end up with no clearance. Of course you can/ should
specify the outer piece as "minus none" and "plus something" and vice-versa
on the inner piece. But I always found that machinists liked talk to you
about you are doing. They might not understand the physics, but they
understand the mechanical parts, and they can often make design suggestions
you haven't thought of. So I would visit the shop with sketches and
half-finished drawings, and ask for advice. Of course this only works in an
environment where you can talk to the machinists face-to-face as opposed to
simply submitting finished drawings.