FreeLists / pcdlist / [pcdlist] Thru hole components

["Watt, William (sys) USX" <wwatt@xxxxxxxx>]

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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