Newb question: how difficult is this?

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adamg

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Buddy of mine has a gunsmith-fit barrel for his bolt action, meaning the gunsmith cut the action tenon and muzzle threads.

Turns out the 5/8x24 muzzle threads aren't cut quite deep enough, so one brand of muzzle brake goes on, but another won't.

I know 'only what I've seen on youtube' about lathes. But to me, this would be very difficult to go back, put the barrel on the lathe again, and cut the threads deeper, because the "timing" of the feed mechanism is hard set relative to the chuck. So you'd have to position the barrel in the chuck within like 1 thou for it to cut the same path again.

Is there some feature or technique I'm not aware of that makes this easy?

I guess the other question is, how easy is to to buy a 5/8x24 die thread cutter?
 
It's pretty easy, just set up the tpi and engage the carriage for threading then use the compound to get the insert inplace and cutting on the leading edge then go how ever much deeper you want the threads to be.

A die would also work and if you use it backwards you could thread right back to the shoulder.
 
I do it essentially the same way as Evanguy, although I'll back off the compound and make a pass without cutting, just to make sure my setup is good.
When I install a brake, I cut the threads and install the brake that is going to be used. I thread the barrel for that specific brake. I don't worry about any and all brakes fitting. In your friend's case, is it the barrel or the second brake that is the problem?
The threads could be chased with a die. Then they would be standard 5/8-24, and most anything should screw on.
You shouldn't have any problems buying that die, although it likely won't be at your Canadian Tire or Home Hardware.
A 5/8-24 die is about $36 at kbctools.ca.
 
If the variance is the muzzle device, I'd investigate there first. How about nipping off the offending portion of the muzzle brake, before trying to reindex the threads on an entire barrel.

(I misread the first post and changed my answer)
 
OP

Don't fool yourself, cutting existing threads deeper, is way more problematic than the answers above indicate and it is super easy for it to go wrong.

For sure it can be done and I have done it numerous times, but it takes some tweaking and screwing around to get the cutter right in the middle of the thread. This is not something I would consider letter a newbie try, even if they have the lathe. It is an advanced technique for experienced machinists.

The safest method would be to buy the die and you'd also need to have the correct sized die wrench. That will be a fairly expensive solution in comparison to just using the muzzle device that actually fits.

You could also try running the correct sized tap into the muzzle device that doesn't fit. Altering the muzzle device is way easier, less expensive and less prone to errors than modifying the muzzle thread on the barrel.
 
^ always modify the cheaper/easier to replace part, especially if the chances of #####-up are high.
 
Picking up a thread and cutting it slightly deeper is a precise job, not for a first time beginner... And there is the question of how much deeper...

I never liked threading for a brake I did not have on hand to check for a precise fit.

I always ran a tap in any brake before threading the barrel.

It may be the easiest for you to buy that tap... run it both ways...
 
If there’s already a thread on it then pick up a split die and chase the threads. If you adjust the gap you can close up the die and take another cut until it’s perfect pitch. This is what I like to use even after I cut with the lathe then finish it up with a nice precise cut with the split die.
 
Cutting existing threads can be done, but is fiddly and can go wrong. As mentioned above the tool is aligned to the existing threads with the compound, but in practice this does take some work.

Also- important to confirm what part of the thread isn't fitting- major or minor diameter... Will indicate what needs fixing. It could be the brake that is what is "out:.

Do you have the ability to measure the bits and compare? Looking at the difference between the two brakes will give a clue.
 
guntech said:
Picking up a thread and cutting it slightly deeper is a precise job, not for a first time beginner... And there is the question of how much deeper...
Click to expand...

I thought about it after I posted and the same question or issue came to mind. The difference between a thread that doesn't fit and one that does can be as little as 1 or 2 thou.



I never liked threading for a brake I did not have on hand to check for a precise fit.
Click to expand...

I would refuse to do such because of the high probability of it not fitting.
 
I Dont Care About You said:
OP

Don't fool yourself, cutting existing threads deeper, is way more problematic than the answers above indicate and it is super easy for it to go wrong.

For sure it can be done and I have done it numerous times, but it takes some tweaking and screwing around to get the cutter right in the middle of the thread. This is not something I would consider letter a newbie try, even if they have the lathe. It is an advanced technique for experienced machinists.

The safest method would be to buy the die and you'd also need to have the correct sized die wrench. That will be a fairly expensive solution in comparison to just using the muzzle device that actually fits.

You could also try running the correct sized tap into the muzzle device that doesn't fit. Altering the muzzle device is way easier, less expensive and less prone to errors than modifying the muzzle thread on the barrel.
Click to expand...

Oh hells, no it is not. If you can CUT threads, you are well above the monkeys that FEAR them!

BTDT, and taught as many apprentice tradesmen or women, that were willing to pay attention to it, how to do it. Same as picking up and continuing a threading job you got greedy on, and chipped off the tip of the tool bit.

Magnifying glass, and some patience, and any amateur can make good on picking up the thread already in place.

Gonna take a few passes dicking around, but as soon as you can make the connection between the cross slide and compound make sense, you will pretty much be on it like white on rice!

Adjustable dies or a tap, are far easier, but picking up a thread after you have centered the bore, is a mugs game, ie: easy!
 
With respect to cutting threads to fit a muzzle device, or a barrel to a receiver, etc...
I will cut the threads to fit. Not cut threads to a nominal specified size. I don't own a thread mike and I'm not going to mess around with my three wire set.
 
I have seen more threads go in cockeyed using a hand die. Even chasing a thread can be dicey if you’re not careful. If you can cut a thread on a lathe you can pick one up and chase it. I would do the tap route first. Then I would just give the barrel thread a slight polish with a piece of emery cloth by hand in case the peaks of the thread are burred.
 
tiriaq said:
With respect to cutting threads to fit a muzzle device, or a barrel to a receiver, etc...
I will cut the threads to fit. Not cut threads to a nominal specified size. I don't own a thread mike and I'm not going to mess around with my three wire set.
Click to expand...

I've seen a 3-wire set used and I want to say I owned a set at one time. A 3-wire measurement takes at least three hands and maybe more. Talk about an insane balancing game. :(
 
It sounds like it's right on the edge of tolerance. Just chase it with a 60° file until brake #2 fits as well. Also chase a tap through that one first.

I've spent easily 18,000 hours of my life in front of a machine.
 
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