Richard,
The gauge pin measures the virtual condition (virtual size) of the hole.
If the customer specification requires a gauge pin, then you are
actually measuring the combined effect of size, drill wander, and
profile of the hole. Therefore, a hole that measures within diameter
specification at every horizontal section of the hole, may or may not
allow a gauge pin to pass through, if the there is enough variation in
profile and drill wander. It is mutually beneficial for customer and
supplier to spell out these details on the drawing using ANSI Y14.5 and
drawing notes.   SOP should be based on what will provide a functional
reliable part.


[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.
>
>      Rich Olsen
> ------------------------------------------------------------------
>      Richard Olsen                Telephone (602)-232-9154
>      Continental Circuits Corp.   Main      (602)-268-3461
>      3502 East Roeser Road        Fax       (602)-268-0208
>      Phoenix Arizona              Pager     (602)-310-6245
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>      USA                    I make circuit boards,what do you do?
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