Making internal thread carbide tool

[Larry$]

I'm making some arbores for a Max spindle sander. Need to internally thread for a 3/4" -16tpi "nut."
After a failure at making a o-1 tool and attempting to heat treat, I found a dull 1/2" two flute router bit in my Junk collection.
I milled away the steel from behind the carbide that I wanted to remove. Then just broke the carbide away.
On the tool & cutter grinder I reduced the diameter for clearance and ground the carbide tip with a diamond wheel.
I got a good 60 degree on the end but had to do the inside angle free hand. Got enough back relief and compared to a fishtail gage. Looked OK.
Drilled, bored & knurled a piece of steel for the nut. Set the gears for 16 tpi and it worked.

 

[benmychree]

I use threading tools from Bokum Co. I have never needed carbide tools for any threading, they are available, but to my experience they chip all too easily.

 

[Larry42]

Should have noted I milled flats so it would always go back into the holder the same way.

 

[epanzella]

I make my internal threading tools out of 01 square stock so the rake angle is consistent.

 

[Larry$]

01 square stock

I've got some O1 but have not mastered getting it hardened and tempered.

 

[Technical Ted]

Nice tool and good grinding work! Good job!

That said, I'm with John and prefer HSS for threading, both internal and external. Maybe it's an older timer thing? I made up a small diameter boring bar that holds 1/8" tool bits that can go quite small internal threads. If I need smaller, I'll grind one up out of a square HSS tool bit. That's a piece of cake on a T&C grinder once you figure out how to position the tool bit for proper grinding. I use a universal grinding vise on my T&C grinder. They can be ground by hand as well, but a T&C grinder is a lot easier!

Ted

 

[epanzella]

I've got some O1 but have not mastered getting it hardened and tempered.

I had poor results with hardening and then tempering. Then I tried just hardening the 01 and using it like that. It worked great. I turn the 60 degree point on the lathe then mill off slightly more than half to get clearance. This results in two cutters. Then I grind off one cutter to get it to fit in a smaller bore. If you're doing big bores you can leave the front and rear cutter. I use it for threading for the breech plug in my SML builds.