On Feb 7, 3:43*pm, whit3rd wrote:
On Feb 4, 3:38*am, "Rick Samuel"
wrote:
[about brad point drill bits]



*Correct, not for metal. *It's a good buy, picked up a box last year, on
sale. *They won't walk off like a twist point

While they may not be intended for metal, brad point bits are nicely
suited to soft (aluminum or copper) metal sheet drilling; the
holes are much neater than with standard drills. * On full
thickness metals, or brass, they don't work as well.

There are brad point bits, and there are brad point bits.

Sheet metal workers often ground their own brad point bits. Typical
general purpose metal bits are ground at 59 degrees, so that the angle
between the cutting edges is 118 degrees. The sheet metal bits were
ground with an angle between the cutting edges of maybe 140 degrees,
but in the other direction, and with a brad point in the center. The
point centered the bit and the edges scored the circle. They work a
lot better than regular metal cutting bits, which don't cut round
holes in thin materials. Some of the woodworking brad point bits sold
today are of this type.

The other type of brad point bits are for woodworking only. The
cutting edges are ground at around 180 degrees, but spurs are left at
the outer edges. The spurs cut cleaner in wood than the sheet metal
bits do. They are more delicate, though, and I wouldn't use them in
metal.

John Martin