I wish I could agree with your technique but I have to go on the side of
your customer. We use minus pin gauge sets. I'm not exactly sure what
the spec is for "minus" pin guages are but as I recall they are 0.2-0.3
mils smaller than the nominal pin diameter. In the case of your example,
a 0.039" minus pin passes through with moderate pressure then the hole
is 0.039".
Hans Rohr
p.s. I also make printed ciruit boards
[log in to unmask] wrote:
>
> PCB Suppliers,
> Continental Circuits (PHX) generally pin gauges holes to determine the
> actual size. Our SOP has been to use a pin
> .001 smaller than the bottom of the tolerance. That is, for a .043
> +/-.003 hole we would use a .039 pin. If this passes through
> with normal pressure, we say the hole is at least .040 and is in
> tolerance. I can't find this technique documented anywhere and have a
> customer who disagrees. They use the same size pin as the bottom of
> the tolerance.
>
> How do you measure holes? I could use some support for our method.
>