On 2013-04-27, wrote:
Got any tricks for a guy to evenly "Tri-cut" the butts of 1/2"
drill bits that basically has no machinery?

Draw filing, grinding whatever, don't care I mostly need a way
to index 'em.

What ideas you got popping out? xD

Pick up a collet block set (there are two forms -- square and
hex), and some 5C collets to fit the drill bits (just a 1/2" one
apparently). Clamp the bit in the collet with the shank sticking out,
put the collet block in a vise, and set up a pair of rollers made from
ball bearings on either side. The bearings will limit how far down a
file will cut. When one flat is cut as deep as the bearings will allow,
loosen the vise, rotate the block two flats and clamp it again in the
vise. This is a way to do it with no power tools, at least. This
should get all three flats the same depth, so the drill won't run off
center.

If your "grinding" includes a surface grinder (not likely with
the "basically no machinery" restriction, just the collet block, the
collet, and the mag chuck in the grinder should be all that is needed.

Good Luck,
DoN.

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