You need to go with a tolerance of .008 dtp.  Most of the vendors
     should be able to build the boards with this number.  .006 is
     especially tight for large quantities.  You should also ask your
     vendor to provide you with a capability study of there drill
     operation.  If your supplier has one and if the sample size is
     considerably large then you will see that .008 dtp is the way to go.




______________________________ Reply Separator _________________________________
Subject: Re: [TN] PTH Positional Hole Tolerance
Author:  "TechNet E-Mail Forum." <[log in to unmask]>, at corp
Date:    3/13/98 6:04 AM


We used to spec the same tolerance. Never heard a peep of complaint from
most fab houses, the only one who complained was known by engineering to do
a poor job generally (but loved by our tight-fisted purchasing agent).

Jay DeKing
EMA Mid-Atlantic, Inc.
(716)334-2970 voice
(716)334-3481 fax
[log in to unmask]

-----Original Message-----
From:   Richard G Smith [SMTP:[log in to unmask]]
Sent:   Friday, March 13, 1998 8:26 AM
To:     [log in to unmask]
Subject:        [TN] PTH Positional Hole Tolerance

     Hi All,

     Here's the issue:

     We specify in our fab spec that all holes are to be within .003" of
     their corresponding pad center (true position of .006"). We are being
     told by our fab house that this tolerance is unreasonably tight.

     Any comments???

     Thanks,
     Rick

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