Cutting some flats on drill shanks can be aided with a spare chuck and/or a
big hex nut on the opposite end for indexing the 3 positions.

A magnetic pointer made from wire, and attached to the vise or other
drill-holding part, can be used for a reference point.

One could choose a feature on the drill chuck that appears in 3 positions,
or the points of a big hex fastener coupled to the drill to index each
position.

A relatively simple fixture consisting of an adjustable slide could simplify
the 3 flats grinding task with the flats being a more precisely uniform
depth.
Making the flats the same depth is also practical, otherwise the drill point
may orbit around the drillpress spindle's axis.

The commonly available stones for rotary tools such a Dremel have abrasive
that's so fine, that it's not likely one would accidentally grind off too
much material.
Checking the flats' depths with a caliper or micrometer would gage
uniformity.

--
WB
..........


"DoN. Nichols" wrote in message
...

A few years ago I tried to "roll my own" flats on a spade bit without
using
the above mentioned tools. You can probably guess as to how that
experiment
worked out.

Well -- you could do it with a file while holding the shank in a
vise, but the trick is getting the three flats equally spaced around the
shank.