Core seating die.

[just bill]

What diameter ream should I use prior polishing/lapping should I be using to make a core seating die? The point forming die is .358. I was thinking about .356 but don't know how difficult it would be to lap .002 .
Thanks ,
Bill

[lead chucker]

The core seat die should be at least a thousandths smaller than your point form die so the point form die can bump it up to size. Makes the core jacket a tighter fit.

[lead chucker]

.354 to .355 that way you can polish it to size. That way you can get any scratches out of it from the reamer.

[NoZombies]

It depends on how deep the scratches and machine marks are. You want to end up about a half thousandth under final point forming diameter.

[just bill]

Thanks, my thoughts were .356, however I have never lapped/polished steel, only homemade aluminum core molds.
Bill

[lead chucker]

half thousandths from finished would be better. The better you polish it the better every thing ejects from the die.