I tried to drill a 3/16" cross-hole in a small steel cylinder (0.3125"
diameter,
0.400" length). I clamped the cylinder by the ends (faced-off and therefore
parallel) in a fairly substantial drill press vise, lined up the center and
center-drilled first. Then I tried drilling the hole with a new 135 degree
split
point drill. The whole assembly started shaking, squealing and in spite of
much
cutting oil a lot of smoke developed. The drill run at appx. 800 rpm ( a big
floor drill).

I made it through by gritting my teeth and closing my eyes. Afterward I
examined
the drill with a magnifying glass and found what I think are small pieces of
steel welded on.

An identical drill from the same vendor has no difficulty drilling into
steel
otherwise.

This is not the first time I have had a problem cross-drilling holes. The
clamping arrangements were different but the ensuing effects were pretty
much
the same.

I cannot understand why this is happening given the solid nature of clamping
and
all the other factors. I cannot see where flex would occur to produce the
extreme form of chatter and subsequent rubbing (which is surely where the
smoke
and welding effects come from).

It was suggested to me that the part gets distorted as the drilling
progresses. It is certainly possible however, the noise etc. starts almost
as soon as the drill hits the piece.

I has occured to me that drilling round stock is essentially an interrupted
cut until the drill has a chance to sink into the piece fully and engage the
flutes 360 degrees. In that case, however, I would have expected the noise
etc. to abate which did not happen. Perhaps by that time the drill is too
damaged?

What is it about drilling cross holes in small parts that causes these
things to happen?

I have tried different clamping arrangements in the past with essentially
the same result. I could not really see any other way to clamp this piece
differently considering its size and the size of the hole.

To solve this I can only think of drilling with progressively increasing
drill sizes (for 3/16" !!!?) or clamping the piece in a 4-jaw chuck and
drill it in a lathe.

Any other explanations or suggestions?

--
Michael Koblic
Campbell River, BC