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August 1997

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Subject:
From:
Hans Rohr <[log in to unmask]>
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Date:
Tue, 12 Aug 1997 21:00:57 -0400
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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.
>


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