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December 2000

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Subject:
From:
Robert Lazzara <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 20 Dec 2000 22:06:26 EST
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Lin -

We use pin gauges. The type most common are known as "compensated", and are 
either "plus" or "minus" compensated. 

Because it is theoretically impossible to fit a true 50-mil pin into a true 
50-mil hole, a 49-mil pin is the largest acceptable size for a 50-mil hole. 
Again, in theory.

Compensated pins relieve this confusion. A "minus" pin is the face value of 
the pin, minus .1-mil . Thus the slightly smaller 50-mil pin will fit into a 
50-mil hole.

But pin gauges pressed into holes have much room for application error when 
weighed in the world of gauge reliability and repeatability. If it's snug, 
give the pin a wiggle. Have burrs, protrusions? Pin gauges make for handy 
point-of-measure reamers in soft solder.

For my time & money if I need to make a few critical, nondestructive 
diametric measurements I grab an optical loupe of at least 10X with a 
reticule bearing a scale not broader than 5-mil increments, then backlight 
the hole.

Cheers!

Bob Lazzara
Circuit Connect, Inc.

In a message dated 12/20/00 9:33:20 PM Eastern Standard Time, 
[log in to unmask] writes:

<< Hi, TechNetters,
 
 Does anyone know about the captioned metters and would offer me the answers
ʣ 
 > When measuring a hole dia., let's say a hole of 46+/-3mil, some  of our
 > customers use a calliper gauge of 50mil to measure. If the gauge passes,
 > they say it is unacceptable ( tolerance included). Some use a 49mil gauge,
 > if the gauge passes, they also say it is unacceptable(tolerance excluded).
 > 
 I would like to know  if IPC has any specification on the measurement and
 what result is accepted? 
 
 > Lin Ting
 > QAA  Engineer >>

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