Get yourself one of those $50 indexers, clamp it at an upward angle in a
vertical mill, and you can cut the teeth and the relief at the same time,
with a little imagination. Index, cut, index, cut. I had always thought I
had an exclusive on these things. (pout)

RJ

"Don Foreman" wrote in message
...
This will probably be boringly obvious to most readers, but I'll post
it in the hope that it might be useful to a few because it worked so
well for me.

I wanted to cut some .700 dia holes in .062 aluminum. After trying
some other approaches I tried making a shop- expedient trepanning
tool.

I turned a bit of 3/4" barstock down to .700" OD, drilled it out 5/8"
and milled slots in the result. No rotary table, just V-blocks in
the vise and X-Y movements. Each slot was made so the cutting edge
thus formed was square, OD of 1/4" endmill moving radially from the
center of the workpiece. I then hand-ground a bit of relief, rake
and bevel (so it penetrates OD before ID) with a Dremel running an
abrasive cutoff disc.

Material was 12Lsomething free-machining steel. I love that stuff!

I case-hardened it with Kasenite which seems to work OK on 12Lxx,
A sharp new file skates on the hardened part. This precision
process consists of heating with an O/A torch until orange, plunging
into the can of Kasenite, heating again to a glowing glob of orange
for a couple of minutes with the garage door open so the smoke had
somewhere to go, and then plunging into a margarine tub of water.
After quenching, I poured a wee dram of Menard's finest muriatic acid
($1.98 a gallon on sale) into the margarine tub to pickle off the
oxides for a few minutes.

I don't think I spend an hour making this tool.

This quick-a-minnit tool works far better than any holesaw I've ever
used. It goes thru 1/16" al in a few seconds at 135 RPM with only
mild pull on the quill and a drop of cutting fluid on the workpiece,
cutting a nice curly chip and leaving a clean and nearly burr-free
hole. I made a slot for poking the slugs out of the center, but
wouldn't have had to. They about fall out when picked with a scribe.

Photo sent to the dropbox as "holecutter".