is there a way to keep the hammer from unscrewing itself as you
work? Or is there a hammer handpiece that addresses this problem
with, say, a set-screw?
The GRS hammers use set screws. But they are air hammers, running on
the GRS machines, not a flex shaft. The fordom power graver also uses
set screws, and it’s essentially a powerful hammer handpiece. But
it’s a whole system, not just a handpiece.
On most handpieces, the two solutions I know of are 1: tighten the
bit really tight. Use the hole in the bit to wrench it down. This
works if you don’t change bits often, and so long as the threads on
your bits are still reasonably good. 2: in use, hold the tip of one
finger on the bit, not just near the end of the hammer. Actually, I
like this anyway. The bits don’t need to be moving much, only
delivering their impact. Holding a finger tip on the bit reduces the
actual travel of the bit back and forth while not much reducing the
impact. The result is increased control over where the bit is
hitting, while at the same time your finger is keeping the bit from
unscrewing itself, which as you note, is REALLY annoying.