The number of different drill sizes on a panel has been a bone of
contention for a long time. In our fab shop we have a list for drills of
over 300 sizes! This is ridiculous. Asia and Europe only use metric sizes in
.05mm increments which cuts the list by more than half and they do fine.
When you send a design with over 30 different sizes, you not only raise the
cost but you increase the time required to drill. You have to remember that
not only do we have to contend with more drill bits in the kit, we also have
to deal with different sizes many of which will only drill a handful of
holes per order. Our shop maintains an inventory of over 200,000 drills. Can
you imagine what it would be like if we had partially used drills in the
inventory, all with different hit counts left?  The standard process now is
to send the used drills to repoint (or recycle) without regard to how many
hits the drill has made, whether the drill has 20 hits or 2,000. As you can
well imagine, this is very expensive and guess who pays for this in the end.
Also keep in mind that everyone of the drills kitted for a job is an
opportunity for failure. One more point - by now, I would say all the drill
machines in use in North America have automatic tool change, but without
exception, tool change time is NOT drill time. The less time you spend
changing drills, the more time you spend making holes.
     Talk to your fab people. They will be more than willing to help reduce
hole sizes on your designs. In fact, this would be an excellent subject for
an industry wide study. No matter how large your company is, the fab houses
have to deal with a lot more companies than just yours. Now is the time to
allow the fab houses to reduce cost, improve quality and get the product to
you quicker, and to reduce your costs in bringing your product to market.

-----Original Message-----
From: Stuart Chessen <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Saturday, September 26, 1998 7:36 AM
Subject: [TN] Increase number of drill sizes


>     Over the past year we have upgraded our CAD library. Each component
>     has it own pad and/or hole size in the library. I have noticed this
>     has doubled the number of different drills needed compared with
>     previous boards layout in years past . Some of the drills sizes only
>     vary by .003".
>
>     What problems is this causing for the board fab house?
>
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