Well, if you’ve got a 20K motor, and you need to stay under 5K, no
faster than quarter speed.
Silliness to the side, the rule with hammer handpieces is slow.
Especially as you’re learning, you want to be able to hear (and
control) each strike.
So it should be ticking over like ‘tick-tick-tick’, rather than
"burrrrrrrrr". If you can’t hear each individual strike, you’re
going too fast. If it gets anywhere close, you’re probably going
faster than you can control anyway. When you get better, you can
speed up, but not at the beginning. (That’s for bezel closing-if
you’re using it for diamond stippling, a slow ‘burrrrrr’ is OK. You
don’t need to hear each strike for stippling, but you really want to
make sure you’ve got control if you’re using it to bash on a stone
The ‘old school’ trick for keeping them slow was to use the old CC
motors that had the reduction gear on the back. Gave more power, and
got the spindle speed down to where you almost couldn’t over-rev
them. Haven’t seen one of those (besides mine) in years, but they’re
nice if you can find one that still runs. They probably float across
ebay every so often, and probably not for that much.