how can i improve the finish of my bbl threading

[rsmithsr]

most is bbl 416 ss..but i have done cm.

I did not see mention of the type of barrel steel being machined. Is it a 416 SS or a Chrome moly steel?
Does it make any difference regarding the cutter material, rotational speed, or feed?
Centerfire

[GeneT]

Watch "Jet 1024 Threading To A Thread Relief Aided By A Proximity Sensor" on YouTube
https://youtu.be/1D-HoFgNYFg

Nez, you have some interesting videos (and not padded with 6 minutes of vapid blather!). I wish you would put a small description on them as I sense a nugget of wisdom in each. Watching the one where you were (apparently) checking the squareness of the front of an AR upper receiver - I'm very curious if you have more data from doing this. I'm looking to confirm my prejudices, of course. I maintain that most uppers are square and that the lapping kits I've seen for sale are a useless gimmick. BUT, I've only had the opportunity to check a few (all square). Have you found any that are seriously out of square with the bolt passage?

Regards,
GsT

[NezRongero]

Gene,

Thank you for the kind words.

The worst I have seen is about 0.003 and front sort of rounded, that it took about .004 to clean up. Some of the other problems with the ARs are the barrel extensions. I can check everything including thread runout like Jackie described at one point, but when BE is screwed on and indicate it, it will be swinging 0.003.

Do all these matter, hard to quantify, I have not done any systematic testing to validate any. I put them in the it-cant-hurt category. I am not in the business, I am retired, time I have. Supporting 18 kids in the State Team keeps me busy.

If you can believe this guy, this is so far the only write up I've seen on incremental improvements on the platform verified on a machine rest.

Maximizing The AR-15: A former military armorer reveals his secrets for cutting AR-15 group sizes in half. - Free Online Library
https://www.thefreelibrary.com/Maxim....-a05207138981

These were taken last night, the kid wants to see how straight his barrel is. Thread was cut with uncoated carbide laydown for Aluminum at 34 RPM on the variable speed 1440, untouched, just cleaned up thread with brush, and air blown. The BE is pretty straight. Got it from WOA.


Watch "12 Aug 2020 Testing Thread Runout" on YouTube
https://youtu.be/CEFUO028lVI

Watch "12 Aug 2020 Testing BE Runout" on YouTube
https://youtu.be/CM434kOxx0s

On squaring the AR10 face I have been using a split ring (borrowed from Mike Bryant) and TS spider screwed on to a Royal live center.

[GeneT]

Gene,

Thank you for the kind words.

The worst I have seen is about 0.003 and front sort of rounded, that it took about .004 to clean up. Some of the other problems with the ARs are the barrel extensions. I can check everything including thread runout like Jackie described at one point, but when BE is screwed on and indicate it, it will be swinging 0.003.

Do all these matter, hard to quantify, I have not done any systematic testing to validate any. I put them in the it-cant-hurt category. I am not in the business, I am retired, time I have. Supporting 18 kids in the State Team keeps me busy.

If you can believe this guy, this is so far the only write up I've seen on incremental improvements on the platform verified on a machine rest.

Maximizing The AR-15: A former military armorer reveals his secrets for cutting AR-15 group sizes in half. - Free Online Library
https://www.thefreelibrary.com/Maxim....-a05207138981

These were taken last night, the kid wants to see how straight his barrel is. Thread was cut with uncoated carbide laydown for Aluminum at 34 RPM on the variable speed 1440, untouched, just cleaned up thread with brush, and air blown. The BE is pretty straight. Got it from WOA.


Watch "12 Aug 2020 Testing Thread Runout" on YouTube
https://youtu.be/CEFUO028lVI

Watch "12 Aug 2020 Testing BE Runout" on YouTube
https://youtu.be/CM434kOxx0s

On squaring the AR10 face I have been using a split ring (borrowed from Mike Bryant) and TS spider screwed on to a Royal live center.

Thanks for the response and the links.

GsT

[Dave Tooley]

I did a lot of work for one manufacture that used a BE for a large caliber bolt gun. Being the curious type I immediately started checking the BE's. Curious = CYA some of the time. All it took was one and I went through 123 to get 30 I would use. Those 30 barrels showed a marked improvement in accuracy over previous barrels. I checked concentricity as well as run out on the inboard and outboard side of the shoulder. They changed suppliers and the story had a happy ending for the next 400 or so barrels.
Some of the same people involved in that project moved on to other companies and now I get good extensions for their piston gun.

[Butch Lambert]

Thanks for the response and the links.

GsT

Gene, I just received my Wife's upper that Nez built for her. Work is over the top!

[killswitch505]

Please allow this rookie to participate. I have a dedicated Jet 1024 for chambering AR15 barrels with compound sort of permanently set for taper boring. Even with this little lathe I thread plunging in with the cross slide. I use laydown inserts for aluminum. They cut 416 SS real well.

Watch "Jet 1024 Threading To A Thread Relief Aided By A Proximity Sensor" on YouTube
https://youtu.be/1D-HoFgNYFg

What kind of repeatability are you getting from your prox? I went with a 5 micron limit switch I’m getting about .0005 at 150 rpm
https://youtu.be/Ncc72aKgzVY

[NezRongero]

What kind of repeatability are you getting from your prox? I went with a 5 micron limit switch I’m getting about .0005 at 150 rpm
https://youtu.be/Ncc72aKgzVY

I don't have a DRO on that 1024, just a dial indicator. It gets to 0.001 or whatever you can accept as the repeatability of the dial indicator. I set the indicator to zero where I want to stop for a given RPM, needle stops on zero. What that is in actual precision, never bothered to verify and don't have the means to do so. So, I just accept what the dial indicator is telling me. For threading to a relief, it is more than adequate.

I do not use the prox to turn to shoulder.

[killswitch505]

Shoot man that’s why I built mine takes the pucker factor out of threading to a shoulder I went from threading at 70 rpm to 300 ive kind of settled at 150rpm and I never have to disengage the half nuts

[NezRongero]

Shoot man that’s why I built mine takes the pucker factor out of threading to a shoulder I went from threading at 70 rpm to 300 ive kind of settled at 150rpm and I never have to disengage the half nuts

I do thread to shoulder when I have to, but thread relief when not needed depending on the barrel extension or flash hider/brake/suppressor adapter. Some have reliefs, some don't. The only bolt gun I ever work on is my brother's glued VFS. That I thread close to the shoulder so when I set back the barrel the extended thread looks decent. It does not make a difference if the thread is interrupted, it just looks pleasing when there is not a big gap between the old and the new thread.

Here is what I use when working on my brother's barrel. See how close the center tip is to the right side edge. I spec'ed it for Thinbit to make for me. The item is not a catalog item, but modified from existing design.

[brickeyee]

Many of the threading tricks (like upside down, backwards, etc.)
are ways of trying to get a little more precision out of lighter weight
(and strength) machines.
Most of the work on smaller fasteners would be done using a
screw machine cutting lathe.
They are optimized for smaller threads.

Sharp steel (HSS is better) works better than carbide especially in smaller tool sizes.

Having some carbide around can often be handy.
Make initial rough cuts using carbide, then switch over to HSS SHARP tools.
No point in making most of the cut with that carefully sharpened HSS cutter.
The wide availability of diamond tooling for sharpening HSS cutters makes things go very well.
A fine diamond paddle for the last few strokes on HSS puts Arkansas stones to shame.

[rsmithsr]

2000 lbs.....

Many of the threading ticks (like upside down, backwards, etc.)
are ways of trying to get a little more precision out of lighter weight
(and strength) machines.
Most of the work on smaller fasteners would be done using a
screw machine cutting lathe.
They are optimized for smaller threads.

Sharp steel (HSS is better) works better than carbide especially in smaller tool sizes.

Having some carbide around can often be handy.
Make initial rough cuts using carbide, then switch over to HSS SHARP tools.
No point in making most of the cut with that carefully sharpened HSS cutter.
The wide availability of diamond tooling for sharpening HSS cutters makes things go very well.
A fine diamond paddle for the last few strokes on HSS puts Arkansas stones to shame.

[Clemson]

Chasing the threads with a die often helps to clean them up, too.

[Pete Wass]

a Hardinge Chucker, I think it's called, with a threading rig on it that is a cam that pulls the tool way far away from the work when it gets to where it is suppose to stop. Slickest outfit I've ever seen. Would speed up threading by at least 1/2 I'd think.

Pete

[brickeyee]

Chasing the threads with a die often helps to clean them up, too.

Firearms seem to be home to MANY 'non-standard' threads.
They are carefully designed for the specific function and loading on a firearm.