On Fri, 10 Sep 2004 11:26:45 -0500, "Robert Swinney"
wrote:

What about using a flat bottomed drill - one at 90 deg? I only did it once
and that was in a 1/4 in. hole with a pilot hole already in place. It was
OK for a brass ball valve seat.

Like an endmill? Thats tough because most drill bits have a
relatively thin web, which makes them very springy and they tend to
walk around. Compare an endmill and a drill bit and you will see the
endmill is far far stiffer. Without stiffness, you need a pilot to
keep it lined up. Ive cut with some sucess (generally poor) using the
spade type wood working bits, but Ive always had to make a small pilot
hole to keep it from wandering.

This bit is NOT recommended for any metals.

Gunner


Bob Swinney
"Gunner" wrote in message
news
On Thu, 09 Sep 2004 01:20:52 GMT, "oparr" wrote:

This is uncharted territory for me. Done similar stuff with wood using
Brad
point and Forstner bits but never with metal. Basically, I need a
counterbore (CB) diameter of about 3/4" to a depth of about 3/8" in 1"
thick
6061 aluminum. This is to create a recess for cap screw head and washer
along with room to use a hex socket on the cap screw.

Sourcing the correct CB and pilot seems easy enough except that MMC
recommends HSS ($$) for ferrous and carbide tipped ($$$$) CB for
non-ferrous
metals. Surely, HSS should work for aluminum or am I missing something?

HSS works just fine for Aluminum. Thats all my CBs are, and I very
occasionally use them on stainless..but its iffy there.

Also, what would be the best drill speed to use in a case like this? I
normally use wax lubricant for countersinking metal, is this good enough
for
counterboring?

at .75, I go about 120 rpm just to keep the chips under control. I
dont worry too much about speeds and feeds with CBs. Too fast is bad.

Finally, is it advisable to buy say a 1/2" aluminum blank and
practice first or am I making a mountain out of a mole hill?

Always drill a practice hole or turn a practice piece the first time
you get a new tool bit, unless you have run them before.

Gunner



"In my humble opinion, the petty carping levied against Bush by
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