In article ,
jim rozen wrote:
In article , DoN. Nichols says...

Of course, the same could be said for any size drill bit, but it
gets rather insane to pilot drill for a 0.100" diameter drill bit. :-)

Not at all DoN - I do this all the time when making small printed
circuit shield enclosures. I want the connectors to wind up in
the right spot, within a few thousanths - so I lay out with
dial calipers used as a scratch gage, under a microscope, and
then centerpunch with a scribe.

For the larger holes I centerdrill with a carbide 3/64 drill
to keep the larger (0.10 inch or so) holes from wandering.
This sort of layout technique will get everthing in within
about five thou and is a lot faster for prototyping than
trying to drag everthing down to a milling machine and sticking
it down with double-stick tape.

Again -- we have a difference in terminology. You are
discussing "spotting" -- to locate a hole.

I was discussing pilot drilling -- drilling a smaller hole
(about the thickness of the web of the larger drill) full depth, to
reduce the force needed to push the chisel point of the larger drill
through the workpiece. For *that* function, there is little point to a
pilot drill for a drill as small as 0.100.

There is still adequate reason for spotting for accuracy of hole
location.

Enjoy,
DoN.
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