Threading fit issue, tapered?

[benmychree]

Answering the last 4 questions -
Threading tool has been a mixture between a standard laydown, and a Mesa Tool vertical (threading away from headstock).
Lathe is an Eisen 1440EV
Everything is tight - Aloris Toolpost
Chuck is a True Bore Alignment System with a Gator 6 Jaw - barrels are indicated in as close to zero as possible - typically only reading .0002-.0005 when done dialing in. After threading, all is still tight and dialed in within range.
Tool height and squareness verified.

Insert (carbide) tools are rarely sharp on the cutting edge and that results in increased tool pressure which can result in taper. I use HSS tools from Aloris that are sharp and easily sharpen able and adjustable for helix. They are available in several widths and pitches (width of flat on the end). They are sharpened ONLY on the top. and last for years in regular frequent use.

 

[WobblyHand]

I'm a fan of the Aloris HSS threading tool. John told me about them a while back. Have three different blades for them. I use them whenever it will fit. They cut very nice threads. And they seem to last nearly forever. I've cut 4 TPI to 40 TPI that I recall with them, beautiful threads for that and everything in between.

 

[jareese]

I do have the Aloris threading tool as well, I have yet to use it. I’ll give it a try and see if it makes a difference.
I have used HSS in the Mesa Tools threading tool, and still see the “taper” of the thread.

 

[mmcmdl]

A picture is worth 1000 words here .

 

[Harry Knutz]

I have minimal stick-out and if I do, then I also use a brass tip on my tailstock. I also run through the tailstock and my TBAS. I'll look at locking the compound once. I've switched to straight plunging in an effort to try and figure this out.. No change in doing so.

Like I said - I'm still within thread spec, but I want it better and I know I can do better. I just need to figure this out.
Thanks for the tip!

I always thread my barrels straight in. Take smaller cuts until you get to the end. Like 1 to 2 thou. Most lathes I have threaded on do what you are talking about.
If you are talking about your action screwing part way on until you take a couple more cuts, That's usually the way it goes.

Zero your DRO after each time you advance the tool, Makes it easy to go back to where you were.

 

[jareese]

I always thread my barrels straight in. Take smaller cuts until you get to the end. Like 1 to 2 thou. Most lathes I have threaded on do what you are talking about.
If you are talking about your action screwing part way on until you take a couple more cuts, That's usually the way it goes.

Zero your DRO after each time you advance the tool, Makes it easy to go back to where you were.

Exactly what’s happening. I’ve started plunging straight in lately as well, paying more attention to my dial, than the DRO.

 

[jareese]

A picture is worth 1000 words here .

Picture of what? The threads? They look great. Taking off 4-8 thou more is what allows the reciever/muzzle device to thread on. You can’t see it with the eye.

 

[Harry Knutz]

Exactly what’s happening. I’ve started plunging straight in lately as well, paying more attention to my dial, than the DRO.

Do the way I just said, Zero your DRO each time you advance the cutter, You'll never go back. Remember too, Depending on whether your DRO is set for radius or Diameter, 1 thou could be 2.

 

[mmcmdl]

Picture of what? The threads?

The set up .

 

[Harry Knutz]

You'll get to where you can wheel the cross-slide in really fast back to zero, then add the amount you want to cut and then re-zero again, Do it that way each time and it will be muscle memory pretty quickly.