Cutting left hand square threads in 416 stainless

[john.k]

Square threads......tricky to cut,I usually cut a couple of narrow cuts ,then sneak up on each side...anyway,a couple of practice trials will show whats needed,and if the lathe will do it.........I would assume any 316 barrel was of a freecutting variey of steel .

[kenton]

FYI 316 stainless and 416 stainless are very different animals.

If you are looking for off the shelf tools a face grooving tool of the correct width can be used to cut square threads.

[Bent Ramrod]

I only did one right-hand square thread job, and that was in CM steel for my rebarrel of a US Krag. I ground the bit according to the specs in Machinery’s Handbook. Old copies of this show up often for cheap in used-book stores, and the old editions are fine for the home shop.

I found that square threads are treacherous. Get an Opti-Visor and check the threads every pass as you get close to size, for burrs. If these aren’t constantly knocked off, you will eventually cut to a “perfect” fit that works one time. When you unscrew the barrel again for finishing operations, the burrs will be squeezed down or rubbed off. The next time you screw the barrel on, it will fit like a hardware store bargain-bin nut and bolt. Having to put a lock-washer between barrel and receiver is not considered good barreling practice.

[Wolfer]

Lots of helpful tips here. My cross feed has no dial or scale and is far too course and loose to feed I with it. I will have to set my compound at 90 deg to the work as it has the only scale on the lathe. I use a framing square to set the compound since there is no scale.

Since time is of no essence to a hog and I’m pretty good at thinking outside the box I’ve had lots of adventures with this old lathe.
Woody Roberts

[Moleman-]

To help remove some of the backlash it may be possible depending on how your nut was made to partially cut through the nut and add a couple cap screws to pinch the cut section. You likely have wear in the middle of the screw, so it is unlikely you'll be able to remove all of the backlash without having it lock up on the non worn sections of the screw. Here's a 1952 Sheldon 13" cross slide nut that has got that treatment. It removed 90% of the backlash except for what is needed because of the wear on the actual screw.

[Wolfer]

Moleman, that a good idea. I’ll look into that

[Moleman-]

Did that 10-12 years ago and I had to tighten it up once a couple years ago. I found the correct NOS nut and screw on ebay listed as "unknown" for cheap and snatched it up for someday when that fix fails. Until then I'll keep using it. Got the idea because that's how the backlash is taken out of the screws on my mill.

[alfadan]

Im not sure but 416 may work harden. Don't let the tool rub and don't futz with a lot of light cuts.

[BS2]

Remember that you need side clearance on the cutter.

[Wolfer]

Update, got it threaded and contoured. No problem. Reamer is not here yet. Just needs chambered, crowned and an extractor notch filed in it.

[Moleman-]

Congrats! You should be pleased with your GMB barrel. So far I've been happy with every barrel blank I've ordered from them. Got two barrel blanks in a couple weeks ago, ordered 4 yesterday and 2 today that had been back ordered since last spring.

[country gent]

Good job, Its satisfying to finish something new.

In your lathe for the cross feed with no dial, Pock ip a 0-1" indicator with a magnetic back. this can be set yp bearing on the upper slide and will give a repeatable zero point and also make back lash easier to remove. Even a magnetic base on the carriage with a 1" travel indicator to the slide will work. But it will measure movement so .001 on the indicator will be .002 on the part. when threading it will llow you to back out on the cross feed an come back accurately.

[Wolfer]

Moleman, this is my 3rd GMB barrel and I’ve been pleased with the others.

Country gent, hmmm, I have one of those.

You all have been a great amount of help in this endeavor and I certainly appreciate it. Thanks
Woody