BFR on the sprueplate thread you mentioned cutting 6 flutes on your mold cherry. What do you use to cut these with?
I made a flute cutter from some 1 1/2" O-1 drill rod brased onto a 1/2" bolt then cut the teeth with a woodruf key cutter. I used it to cut one flute on my 30 Erin chamber reamer, made from 3/8" O-1, and it went dull after the first cut. maybe I need to make it out of something harder. I ended up useing a carbide end mill and just cut 4 flutes on it.

The chamber reamer cut great, but was a bit on the large side. I'll have to make the next one smaller to start with.
Thoughts on cutting flutes??

Lar, I made a brass plate with a flange and setscrew to put on the piece of drill rod. I drilled 6 holes around the outside and put a pin in my vice. I had to locate and drill the side of the vice. I put the rod in my vice with the pin in a hole and when I finish a cut I rotate until the next hole is on the pin. I use an end mill to cut the flutes. Then I reposition the plate to cut another angle and relieve the back of the cutting edges until there is just a fine tiny flat left. Then I stone them back until they are sharp. I file the nose cutters by hand and stone them sharp. I harden the cherry and leave it dead hard. I don't bother to draw them to tool temper. Only cutting aluminum so they won't break. They cut so fast it is scary.

I'd love to see a picture of the rig.
It's something I'd love to do too.

I used a piece of 2x2 steel square stock and put it in my cross table vise. I then put different sized drill bit's in the lathe and bored holes lined up on center into the square block. I then drill and tapped the top for 1/4x20 bolts to use as set screws. After turning the reamer to size, I put it in my block and cut the flute with the mill, then rotate and lock down with the set screw again to cut the next one. The angles don't turn out perfect, but they do cut well. After cutting the flutes, then I turn it so I can use the end mill to make a relief on the back side. I filed and stoned, then used a diamond stone to sharpen after hardening. I might have to try hardening then anealing before turning to cut down on warpage.
I can then use my block to hold the reamer for chambering short barrels as my tail stock won't reach across the cross table on the smithy.

Trk, I have taken some pictures, but I don't have a digital camera so I have to finish the roll and get them developed. Maybe I can get them put on a disk. Then I have to find someone here with a web site to post them. I will work on it.

Lar, a thought, if you get that cutter the right hardness, be careful how fast you spin it. Turn and feed slow with lots of coolant.
I have no provision for coolant other then some cutting oil dripped on because the stuff goes all over the lathe and floor. Thats why I use an end mill.