#### DHambley

##### Electrical

- Dec 7, 2006

- 246

I am looking for a MIL-standard paragaph which calls out the proper way to stack tolerances.

For example, if a part has 4 independent tolerances on an initial value of X:

a 25%, b 40%, c 5%, d 35%

The worst-case value if all of these tolerances stack up in the negative direction would be:

X*(1-.25)*(1-.4)*(1-.05)*(1-.35) = 0.278 by the multipliation rule.

Our customer is insisting that we have to add these, not subtract. In the case above, he would calculate:

X* (1-25%-40%-5%-35%) = -0.05X He would conclude that an intial mass of X with this tolerance stack up could end up with a mass of -0.05X (which is preposterous).

The Question: Do know which paragraph in which MIL-handbook calls out to use the multipliation rule for tolerance stack up?

thanks