Kathy,

Some N.C. drilling machines manufacturers claim that their machines can do
controlled depth drilling with +/-0.001" accuracy. I know that Hitachi is
one of them. I assume for controlled depth drilling the depth of the hole,
hence the tolerance, is measured from the top side of the board. For
dimensional and tolerance purpose, counterbore could be considered as
controlled depth drilling. If the right NC drilling machine is used,
theoretically, you should be able to get +/- 0.001" tolerance.

Sherif Refaat, Eng.

 -----Original Message-----
 From: Kathy Bergman [SMTP:[log in to unmask]]
 Sent: Monday, November 03, 2003 3:46 PM
 To:   [log in to unmask]
 Subject:      [TN] Counterbore depth tolerance

 Hello Netters,

 Any ideas of what a standard depth tolerance of a typical counterbore on a
 PCB might be?

 Thanks
 K Bergman

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