Cutting threads

[25WSM]

The finish looks bad but you have treads that will work. If it already fits the receiver then just lube it good and tighten and remove a few times before your final torque down. Like others have said without knowing your tool bit and speed and lube its hard to point the finger at just one thing. I was taught at Gunsmithing school to run the lathe in the lowest back gear. But i run the highest back gear and the finish will much improve with some rpms. Another mentioned filing the tops of the treads. Great advice. When your barrel just starts to want to go on file tops of the treads down a little. Then try your fit again. If you need to cut the threads more and they point up then just knock them down again. Dont know if you were feeding straight in or if you set your feed at 29.5. Straight in feed causes a ton of tool pressure because its cutting on both sides of the bit as opposed to 29.5 degrees cuts only on one side. Lots of things can cause the rough thread. Try a few of all our tips on a practice piece of stock and play around till they look good. Dont be afraid to take bigger bites at the start. I turn a barrel thread down to the final fit in 7 passes. Then i take small bites to get the fit i want. If your setup is delicate then you have to to take small bites. Good luck on your next one. If your ever near Pittsburgh stop in.
Shep

 

[Dragoon300]

If the OD of the threaded area was at or below the desired diameter, the correct pitch is set and your tool is correctly shaped and on the correct angle, including the compound, your threads are too sharp. The tearing is not good, but will

 

[Dragoon300]

Sorry, hit the post button prematurely.

The tearing probably will not cause a problem. If it fits fairly well in the receiver (not rattling before tightened) you could locktite it in with bearing mount Loctite to take up gaps and it should be ok, but might not come out without heat. However, if it is too loose, don't use the barrel.

 

[jarnold37]

Several years ago, I learned from a well known gunsmith that using a full profile insert would always produce the exact thread depth with no guessing. With a full profile threading insert the insert is for only one thread pitch. It takes a specific insert for a specific thread. When cutting threads for a Remington, nominal diameter is 1.062. With full profile, the tenon is cut to 1.070. Then when threading with a 16tpi insert, make light passes until the insert starts to reduce the diameter as well as cutting the thread. The insert then is cutting the exact depth that is specified for 16tpi thread. Mic the passes until diameter is close to 1.062 and try action on tenon. If another pass is needed still correct until action will thread on correctly.I do cut at a faster rpm with carbide but no problem. I saw a barrel thread from a gunsmith and the threads were very sharp and very loose. Another barrel ordered (ordered 3 barrels) by a friend from a smith several hundred miles away, would not thread on being to tight. He drove hours and the smith smeared valve grinding compound on threads and worked back and forth till threaded on. Full profile insert eliminates that problem. Some thread tendons need to be slightly smaller diameter than nominal and thread becomes wrong depth by cutting another pass or two when problem is tenon cut to big before threading. With full profile there is only one operation to monitor as each pass keeps the correct thread shape and size even if smaller diameter is needed. Grinding my own HSS sometimes went good and cut good thread but sometime not so good. Something not mentioned very much but for barrel tenon it is important for me to cut a correct thread which is more important than surface finish.

 

[parshal]

I started using full profile inserts for all my threading and, as jarnold states, it produces the exact thread depth. Another thing you can do to clean up the threads is 0000 steel wool or a cratex stick. It doesn't take much at all to shine those up and remove the rough surface.

 

[bamban]

I am not totally convinced that carbide inserts had to be ran at high speed. This was threaded on my old Jet 1024 running the lathe with the VFD toggle. This lathe also has a proximity sensor that I can thread at 400 RPMs, which I do most of the time. This a project for a friend while he waited, when the subject of HSS and Carbide came up so I set up threading with the 30 RPM toggle speed.

I had the stick out far enough by design and plunged straight it with the cross slide instead of running the compound. I say not bad for old worn out lathe. Just learn to live with the machine limitations.

I am not a machinist nor a gunsmith by trade, just a retiree hacking away at this machining stuff.

 

[PPR]

It looked good until I saw the pictures. Now I see tearing.

For one thing, the barrel is way to far out of the Chuck! Choke way up on it. Run the fastest rpm you can handle. Run HS tooling. Good luck.

Paul

 

[parshal]

I am not a machinist nor a gunsmith by trade, just a retiree hacking away at this machining stuff.

I also use a proximity stop and thread straight in. Once you get used to it's tough to go back to the old way.

 

[jrock]

I touch up a HSS blank after each barrel. I quickly run it on a hand stone. That helps keep the tool geometry as it's removing very little material. It will leave a great finish.
I've run carbide threading tools at sub 400 RPM with good results as long as things are rigid.

 

[jrock]

+1 on cratex. It's great for polishing threads

 

[Coyote Shadow Tracker]

These videos can be helpful to anyone threading barrels.






https://youtu.be/LKGkkGFsF50

 

[stangfish]

Most important thing is pitch diameter.
If after threading the OD mic's too large when it was turned to correct dimension before threading use sandpaper judiciously to bring back to correct dimension. It is common for insert tools to roll an edge. Use a Cratex stick to polish threads to acceptable finish. I always like to start with making a test gauge to see what the maximum pitch diameter will thread smoothly into the action.

I use carbide based threading inserts and tooling everyday and I have never ran production.

Very few inserts, if any are solid carbide these days.

 

[tobnpr]

However, if it is too loose, don't use the barrel.

"Too loose" is definitely not acceptable- but limited play is fine and preferable to gnat's *** tight threads on the verge of galling.
Dave Manson told me this years ago when I was learning this process that the threads just bring the parts together.
It's the shoulders that align them- and having the barrel and receiver perfectly faced is of greater importance than precise thread fit.

Use a Cratex stick to polish threads to acceptable finish.

Why?

 

[Alex Wheeler]

You can achieve excellent finish at low speeds with carbide. You just have to use the right tool. Trial and error. But HSS is much more cost effective for the hobby guy. And less of a learning curve. Most want to jump into carbide thinking its easier but its not.