A boring table for a Craftsman 12" lathe

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awemawson:
Steve,
A rough and ready tap for single use can be made easily from mild steel, then case harden it. Turn a length of rod to the acme profile you need, taper one end for a lead in, mill four slots axially to provide cutting edges, then case harden it.

This will give a tap with no 'back relief' - so will be easiest to use if you first rough out the female thread by boring, then finish with the crude tap.

If you have no case hardening compound, a reasonable substitute is ordinary table sugar. Heat the steel, plunge into sugar bowl whilst wife is not watching, remove, dip in clay slurry, then heat to cherry red. Keep at heat for a couple of minutes, then plunge vertically into water. The clay slurry markedly reduces the oxidation. Keeping vertical reduces distortion.

Many a set of wire cutters were hardened this way by POWs in WW2

chipenter:
Drill rod makes excellent taps , the easiest way I have found to cut acme threads , is to make a parting tool to fit the thread from round high speed steel , and twist the tool to match the rake of the thread , and a very small in feed .

vtsteam:
Those are both really great tips. Thanks Guys! :nrocks:
I suppose I could make the acme rod to then make the tap.

Before I read the above today though, I already made up a second internal threading tool and set up the lathe for thread cutting. I haven't cut anything yet and will try some test pieces tomorrow. I guess I'll see that through, one way or another. But now have a plan B with the tap tips.

Also, I should admit, Andrew, I have an unused can of Kasenit sitting on a shelf. :palm:

Here's today's and yesterday's cutters compared. I had to grind down the shank of the new one by hand because I had hardened the cutter already and found I didn't quite have enough clearance in the bored hole size -- .420" -- even though the shank was .375. The tooth pushes that out, of course :doh: :

chipenter:
I made one of Bogs tools and found that there was not enough clearance for a coarse thread , and had to grind the front back for 1 1\8 x 11 tpi faceplate , took me a while to figure it out lol .

vtsteam:
Even if this new tool works out, I gotta try making a tap, the way you guys suggest, too. I'm sure it will come in handy, and I have the materials for it, plus the lathe is set up for cutting 10 TPI. It just sounds like fun to me. And I want to try that hardening recipe. Maybe I'll do 3 of them -- then I can try Andrew's hardening mix, try Kasenit, and also do a drill rod version. Cool!

But I better check out what I'm planning with the internal tool -- I didn't have an acme gauge -- and had to find the info for internal cutting in a couple different places here's what I think I'm supposed to do....

1/2" x 10 TPI:

Width of cutter tip was turned to .032"
Angle of sides is 29 degrees
Diameter of hole to be bored in the nut .420"
Diameter of full cut .520"

Please let me know if any of this is wrong! :wack:

Thanks!

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