On 8 Oct 2006 21:12:25 -0700, "Robatoy" wrote:

I am in need of a few sizes of flat-bottomed holes.

The difference between HCS and HSS is well established, and worth the
extra few bucks to go to HSS.
But what about carbide?
Any sets you guys like? ( 1/4 - 1" in 1/8 increments would be fine.)
Lee Valley has a nice set.
Any other suggestions?

In the interest of full disclosure, I have only used the set I own, so
this is not a compare/contrast endorsement.

I've got a $20 7-pc set of "Columbian" brand Forsner bits, and they've
been going strong for about three years. They see a fair amount of
use, and most of the work I do is in hard maple, so I wouldn't
hesitate to buy them again. The cuts are smooth and clean, and they
don't seem to be dulling at all, so I don't see how spending more $$$
would be an improvement. IIRC, they are HSS with a TiN coating, but
they could be carbide- it's been a while since I threw the info that
came with them away.

A few notes on carbide in general, though- while it's very hard, and
doesn't dull easily, you're not going to be able to touch it up with
anything short of a diamond hone. It is also a grained material-
which means that it is tough in one direction, but fairly brittle in
the perpendicular direction. I'm sure they work out the best grain
direction when they manufacture the bits, but you had better be sure
your drill press is pretty steady- I know that when using carbide
taps, even the slightest side-to-side movement can snap even a fairly
stout tap very easily. Don't know about the forsner bits, but it's
something to consider.

For the cost of a high-end set, I think I'd go with the HSS, so that I
had the option to touch them up with a file if they get dull. But
then again, I'm awfully happy with the cheap set. They're perfectly
servicable, and when they do eventually wear out, $20 won't put me in
the poorhouse to replace them.