How do I choose a reamer size?

[alexmin]

What size carbide reamer do I need if I have 0.310 pivot that I want to rotate freely in a hole. (I'll be reaming already HTed CPM 154)
I'll be lapping the hole afterwards with bronze lap and some abrasive compound.

Thanks,
Alex

 

[TekSec]

A .311? Just kidding. At 21/64" is .33 or a 11/32" is .34. Good luck with hardened CPM. Use lots of lube and go slow...

 

[Kiwi303]

Use lots of lube and go slow...

I bet your wife loves ya


a custom gunsmith may have a .312 barrel rifling cutter with a broken shaft, long odds since .303 Brit isn't as popular a cartidge these days, but might be worth a try. using that in a drill press may work.

 

[TekSec]

I bet your wife loves ya

How did I know someone would comment on that?

 

[scottickes]

How did I know someone would comment on that?

Hey, we're knifemakers, not dead.

 

[Nathan the Machinist]

A .311", no kidding. Or a .310" and lap it. Decimal reamers in .001" increments are readily available.

21/64, at .328 is 18 thou oversize which is an order of magnitude too much slop.

5/16, at .3125 is probably just fine.

Any chatter on a carbide reamer and your edge flakes off. Most reamers are very long with straight flutes. You need a very short reamer to prevent chatter, spiral flutes may help (but probably not on something as thin as a blade), and you shouldn't be removing more than about .010", preferably less. I would use low RPM and a steady feed and an oil.

 

[Fellhoelter]

Personally, I'd use a .310 or .309 before HT.
Lap it after HT, but why bother reaming after?

I use a bushing in all my folders, and ream to .375, HT, then lap.