FreeLists / pcdlist / [pcdlist] Re: Thru hole components

["Drew" <drew@xxxxxxxxxx>]

Hello,

I round off all drill sizes except press fit or alignment holes to the =
nearest 5mil.
Only a pressfit or alignment hole will cause me to have a drill size =
that does not end with 5 or 0 mil.
I am not sure how this will work when we go metric.

Cheers!
Drew


----- Original Message -----=20
From: "Watt, William (sys) USX" <wwatt@xxxxxxxx>
To: <pcdlist@xxxxxxxxxxxxx>
Sent: Thursday, May 09, 2002 10:16 AM
Subject: [pcdlist] Thru hole components



Now that I know there are a few people out there, let me ask a question. =
 We
are having a discussion here in our design dept about standardizing hole
sizes.  The present method of determining finished hole size is to use =
the
IPC 2221 formula and pick the hole in the center of the range.  This is =
fine
except we end up with many holes that are within .001 of each other and =
our
mechanical checker or the fab house will ask to combine them into one =
common
size.  I recall from a past life that I used a hole chart with drill =
sizes
every .003 instead of every .001 and this worked fine.  I am having =
trouble
convincing some of my coworkers of the wisdom of this method.  I would =
like
to know if anyone else has an opinion on this. I would like to =
standardize
by using the formula, finding the median size and rounding up to the =
next
drill size.  How does the rest of the world do it?

Thanks for the help.  Maybe I can use an overwhelming opinion to =
convince my
department.

Bill Watt
Moog Inc
Jamison Rd
East Aurora, NY 14052
716-687-5596
wwatt@xxxxxxxx

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