Hi Michael,

> Mark said; It's not too unusual to encounter machining tolerances
of 0.0005" (very good machinists, of course).

> You said; Really? What process are you using that would get you to such a tight tolerance.

In precision tooling, eg. plastic injection moulds, instrumentation, as Mark mentions 0.0005" is not unusual, we at work have NX modelling tolerance set to this figure, this guarantees that there are no gaps in the model because when the CAM guys generate cutter paths to machine the model if there are gaps at 0.001"+ the path will want to jump into that gap thus generating a gouge.

I'm talking about the surface to surface contact tolerance here, when we need a fine dimensional tolerance of a model feature and say it needs to be 0.3755" we would model at the nominal 0.375" and state +0.0005"/-0.0002" on the technical drawing.

BTW at our place we sometimes machine to 0.0002" but normally not over 0.0005".

Cheers