Tolerance

[mu38&Bg#]

I haven't worked at a real machine shop in quite a while. The aerospace company I was at last 10 years ago we put limits right on the inspection drawings, but the shop still made their own manufacturing prints. I think it would come down to how much space I had on the print. If I have countless holes in a part calling an IT fit would be much cleaner than stacks 4 decimal place tolerances. It's all up to the company you work at. Since I work for me right now, the standard are pretty lax.

Of course for modellers, I'd just follow convention in the field and call out only the clearance/interference. You guys would hate me though, my prints would be metric! :hDe:

 

[Mainer]

I pay little or no attention to tolerance specs on what I'm building. Through experience I've learned what kind of fit is needed in which situation (mostly) and build to suit.

For a one-off part, there is also little need to hit an exact dimension. e.g. if a cylinder bore is spec'd at 0.7500" +/- 0.0002," if it turns out to be 0.751" because the last pass with the boring tool took a bit more than expected, I can just make the piston diameter a bit larger to suit. We seldom need to deal with interchangeable parts.

We can and do, however, on occasion work to very close limits. That cylinder and piston may be a few thou out of spec, but they may fit together to within one or two tenths.