I have cut sapphire and other exotic stone with diamond laps.
I never cut metal.

I have hand laps that are diamond - they are used in or with water
and the action is slow. The diamond is either 'used', chips into tiny
chunks or otherwise vaporizes in spite of the water.

Localized points of contact become very hot. Blue white hot. The
diamond
might burn up or change state and then get absorbed.

I have heard of localized hardening.

Martin
--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder