http://www.modelenginemaker.com/index.php?topic=7288.110
It's in my Levin thread page 12
I found your pictures in the thread. Gotta say, I'm kind of surprised that geometry would cut very well. But, nothing succeeds like success!
Chuck
Actually Chuck....it blew me away as well. I found the original thread on Practical Machinist, and it had such acclaim, that I gave it a go Worked great!
You cut the thread on the tap, harden it, then grind 4 flats at about a 20 degree angle. Now I milled 4 flat before I hardened it, but I still touched off on the grinding wheel on those flat faces after heat treat...the angle is not critical at all, but having the small end of the tap go below the root diameter is. This tap needed guidance to get started, so I started it in the drill chuck of the lathe It cuts amazingly well!. I made the tap 0.219 diameter...like the commercial right hand tap I have. I then cut the male thread to 0.218 diameter. It has a very nice fit, with no shake.
Make sure you wrap the tool with iron wire, and either dip in silver solder flux, or liquid soap. This will keep the tool from burning during heat treat.
I used 0-1 tool steel. Silver steel to you blokes over there.
Brighten the tool up, polish the flats, and draw to brown. That's it!
Dave
Dave
