Probability Estimate

From: Philip Holman (namlohip_at_comcast.net)
Date: 12/30/04 

Date: Thu, 30 Dec 2004 09:39:35 -0800

I have an assembly of engineering parts which can result in a nominal
clearance gap of .140 between the surface they are mounted to and the
feature of interest. The eight part stack up has the following set of
tolerances:
Part Tolerance +/-
1 .010
2 .010
3 .020
4 .075
5 .010
6 .010
7 .010
8 .075

Total +/- .220

I'm interested in a rough estimate of the probably of the gap being .060
or less. From a normal distribution curve/table this looks to be .073 if
I assume +/- .220 is zero probability. Is this a reasonable estimate?

Phil H