A boring table for a Craftsman 12" lathe

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vtsteam:
To make the nut I need an acme 10 TPI internal threading tool. I found elsewhere on the forum instructions for making threading tools on the lathe, so I thought I'd try it.

Here's my first effort:

tom osselton:
I remember those have not tried them yet though they should be perfect!

chipenter:
I think it would be better to make a tap , as it is square thread or half a tap similar to a D bit , http://www.rdgtools.co.uk/acatalog/ACME_TAPS__LEFT_HAND_.html the link shows a tap with square grooves milled along the length .

vtsteam:
Tom, Chipenter, thanks -- always looking to try new things (to me). And this site is a great resource for that. Hope I'm contributing something in return. :nrocks:

Chipenter, a tap would have been my first choice, especially since I'm sure I could use it again in the future. But a quick check of the usual machinery resources here in the U.S. showed acme taps of this size (1/2"-10) were approximately $100 :bugeye:
I wonder if they are made of platinum?

I'd seen a youtube vid of a roughly made acme tap, but I don't have acme threaded rod on hand, so would have to order that. Also it can't be hardened, though in this case I'm not cutting steel.

I'm very curious about the tooth shape boring bar turning method -- it's fun and I have drill rod on hand.

Missed the link last post, here it is:

http://madmodder.net/index.php?topic=3523.0

I can see several improvements I could do to my technique after this first one -- mainly to increase stiffness:

1.) the bar should be as wide as possible -- to fit the internal starting diameter of the nut.
2.) the bar should be as short as possible with just enough clearance to pass through the nut and a little bit more to stop the carriage in time.
3.) the cutting profile should be as short as possible, with just enough clearance to clear the cut.
4.) although I have tempered to appropriate colors in the past for boring bars, I believe this one should be made like the OP suggested, dead hard, to maintain the highest sharpness through the cut.

vtsteam:
Thinking about the above, for a 1/2" x 10 TPI thread, I think I'll try this:

1.) start out with stock equal to the nominal diameter -- in this case 1/2".
2.) turn the end button and shank to a depth of 3/8"- which yields about 125% tooth depth
3.) after making the flute flat, grind off the outside turning tooth profile for clearance.

I think that will make a much heavier shank.

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