Blank Mold Blocks?

Anyone built your own molds using blank mold blocks? I would like to know how the process works. I picture a rotating cutting tool getting squeezed between the stabilized blocks. Inquiring minds...

There are a bunch oh how to's on YouTube for homemade bullet moulds and such. Good luck

There are several ways to do a mould from blanks.
Mill
1) use a cherry and double acting vise closing the blocks on the cherry, this is how it was done for many years.
2) set the blocks on a known opening then y axis moves to cut each half, with a dro this is quicker and almost as easy
3) with a cnc they can be done with a ciircle pocket program and undersized cutter.

Lathe
the blocks can be set up in a 4 jaw and bored to shape.

EDM
is basically the same as the last mill one Burn to depth then circle pocket with an undersized electrode. This works well as there is no cutting force, no burrs, and a very uniform finish. There is a lot less stress after machining.

The big thing is accounting for the expansion in the blocks and shrinkage when casting. these have to be taken into account when cutting the mould so that the bullets are to size when cast.

GONRA has "turned over" a set of blocks in a 4 jaw lathe chuck,
used a boring bar(s) to cut another cavity.....
Verks Just Fine! !!

Wondering if you could use a small bullet mold and open it up to a larger size?

Yes you can use a smaller bullet and machine out to a larger bullet. This works better with lathe or cutters than the cherry. But the blocks have to be long enough for the new bullet. On most handgun bullets this may not be a problem but with some rifle bullets it can become a issue.