Chipping Marble (or dolomite)

["George Graham" <georgergraham@zzzzzzzzzzz>]

B.
You don't say how thick your disc is , so I'm assuming that it's kind of
thin. If you are working with stone that is 2 or more inches thick, then you
have to be more cautious.
The best way I know of to control a break is to put a stop where you want
the break to stop. Try making a saw cut straight in to the depth you want,
to the point of the V. Up the middle of the V. Then use your flat chisel on
the edge of the stone , not the side, and try to hit with your hammer to get
a break that will want to run to the bottom of the saw cut. You may have to
go with 2 bites of the chisel for each side of the V. Ideally, you would be
left with very little of the saw cut to be seen at the bottom of the V, and
the chisel marks would be on the outside surface which could be cleanly
trimmed off.
If you don't have a diamond saw blade, get one of those carbide encrusted
hack saw blades and make the cut by hand. Cutting an 1" deep into marble is
no big deal.
Oh, definitely do a couple of practice cuts on some scrap first!!
Hope this helps,
George Graham