Yes, the tolerance zone is a circle. The hole can be anywhere within
that tolerance zone diameter. So if your hole is closer in the "X"
direction, it can be further off in the "Y" direction, etc. Maximum
material condition means that at the smallest allowable diameter of the
hole, you have the given positional tolerance. So, for example, every
.001" that the hole diameter exceeds its minimum, you can add .001" to
the positional tolerance. 

Just a marketing guy now, but I did spend many of the worst years of my
life in Quality in precision machining and sheet metal manufacturing....


Thanks,

Randy Morrison 
Marketing Manager
Pentagon EMS

  

http://www.pentagon-ems.com/bio/randy.html
[log in to unmask]
Tel: 503-924-2747
Fax: 503-924-2744 



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Donald Kyle
Sent: Monday, July 10, 2006 8:10 AM
To: [log in to unmask]
Subject: [TN] Geometric Tolerance

We are having a little debate here as to the interpretation of a
Geometric statement evolving the tolerance of holes on a PCB.

The geometric statement reads from left to right:
Position (symbol)
Diameter (symbol)
.005 (tolerance)
X (datum)
Y (datum)

Some say that this statement means a positional tolerance zone within a
circle.

Others say that this is just another way of stating a bilateral
tolerance zone within a square.

How do you interpret this?

If you have IPC-D-325A you can read about this on page 28 and appendix B
for more information.

Because I don't know how to insert a geometric symbol for POSITION and
DIAMETER you will need to use your imagination here.

  Geometric      Geometric       Tolerance       Datum
  Symbol for     Symbol for                      Reference
  Position       Diameter
        __             __                   .005                 X
Y


Thanks for your time


Donald Kyle C.I.D.+

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