Engraving...

hermes.com has lots of good reading on the subject.
Quick overview of what I think I've learned...

Real engraving spindles turn at 20,000 rpm or much higher,
because a very small diameter tool can't be pushed very fast
thru any material or it will break. Figure on 3 inches/min
for a 1/32 inch dia toolbit. maybe even lower, for a 5,000
rpm typical mill spindle.

The V-shaped cutter is typical for rotary cutting. It will have
an included angle and a tip width spec - read the hermes stuff.
A "D" cutter is most often found on real machines for rotary
cutting.

There is also diamond-drag engraving, which is non-rotating.
Just a point that gouges or scratches the surface.

For rotary, use lubricant - rapid-tap, e.g., for non-ferrous
metals, alumitap is another.

I rigged up a holder for a dremel on my spindle head, which
increases table travel by 6-7 times the speed. If you're
doing small stuff where a thou is an important parameter,
the dremel likely won't be stable enough.

since the surface of the workpiece may not be perfectly flat,
you'll get variable width (due to variable depth of the v-cutter)
as you pass over the high and low spots. Many "real" spindles
are spring loaded so that they apply constant force of the cutter
on the workpiece, yielding better uniformithy.

Use engraver's double sided tape. Carpet tape and other double
sided stuff takes way longer to remove than the engraving takes.
Heat gun or hairdryer helps. I HATE that DUCK brand has taken
over most outlets, their double sided stuff isn't well suited to
workpiece holding. Strong, yes...

I've done quite a lot of experimenting with carbide and HSS
cutters, have had fairly good luck making D-cutters from
broken carbide PB-board drills. Use a diamond wheel to shape
them. I've found that I can make a fairly "polite" drag tip
by grinding to a point, then working it over with a diamond
bearing rubber polishing wheel on the dremel. Smooth, not
surgery-sharp, no burrs on teh workpiece.

Fonts are another challenge - truetypes are outlines only, which
doesn't necessarily look all that great. So, I often will pick a
font with 'fat' vertical portions, then use my cam program to
pocket each letter, which usually produces 'not bad' results.
Set it up so that the lines (drag, usually) are spaced wider than
the dia of the scratch, for best results.

And I'm still learning... At 10 cents a letter, I don't see any
way of getting real rich real fast, at the speed my mill works, a
nd the time it takes for setup and tape-removal...

Vac table experiments will happen soon, I guess.... / mark