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Galled barrel in action

ridgeway said:
For future...take a close look at the lead of the thread. I've seen many times that a tenon lead thread never gets any bench work on it, meaning the sharp crest never gets filed down and burrs taken care of. This is the culprit on many galled threads. Best thing to do is blunt start them, but takes time to do it right...
Click to expand...
The best way is to turn the diameter down .005"-.010" undersize to start with.
 
I have used moderate heat (electric heat gun) and synthetic gear oil. Heat the joint and apply oil through scope mount holes and breech end of barrel. For years, I worked in a hydraulic shop and parts often were made of similar materials and prone to galling. I used to harp at the mechanics to use grease, not oil, on joints. WH
 
DaveTooley said:
The best way is to turn the diameter down .005"-.010" undersize to start with.
Click to expand...
Yep...that is the proper way to turn the major. I am referring to where the lead thread starts. The way the crest angles up to the first full thread. It needs attention with a stone or file. Blunt start would take care of it, but who will take the time to do that, lol

I do know what you are talking about. I've seen tenons turned to exactly 1.062 in diameter and the crest is sharp enough to cut your finger, lol. That's just asking for trouble. The thread needs relief when it mates.
 
ridgeway said:
Yep...that is the proper way to turn the major. I am referring to where the lead thread starts. The way the crest angles up to the first full thread. It needs attention with a stone or file. Blunt start would take care of it, but who will take the time to do that, lol

I do know what you are talking about. I've seen tenons turned to exactly 1.062 in diameter and the crest is sharp enough to cut your finger, lol. That's just asking for trouble. The thread needs relief when it mates.
Click to expand...
I put a 45 degree chamfer on the tenon that's smaller than the root diameter and I polish the first thread.
 
Galling ?

If the barrel thread crests are properly flattened and anti-sieze lube is used----can pitch diameter mismatches cause galling ?

My practice has been to turn the tenon to the specified diameter and remove "some" crest
with a file.

I now understand the wisdom of turning the tenon
down before threading.

A. Weldy
 
Yes pitch diameter can cause problems if it's an interference fit or close to it. There are no negatives to having loose fitting threads.

I also think part of the problem is mismatched thread profiles. One not having a true 60 degree profile and/or not being aligned perfectly perpendicular to the bore. That would increase pressure on a reduced surface area. Of course that's assuming the action treads are correct. Some aren't. I had a custom action where the major diameter of the barrel had to be .030" undersize because the insert used on the action had a broken tip.
 
1FDAEAE3-1A9E-4C05-9670-34892BA60AA7.jpeg The action is already damaged. Your only real fix is to bore the tenon out and then change the threads to true them back up.

Yes, the threads will no longer be “standard”, but you are probably beyond that point. The object now is to make the action serviceable again.

Last year a fellow shooter tried to screw a Panda barrel into his new Bat DS. For those that do not know, Bat uses a tighter pitch diameter than Kelbly, even though both are considered “1.062 18 tpi”. He got it half way in with an action wrench and it stopped. There was no moving it after that.

He took it to someone who ended up boring half the threads out of the action. The action was ruined. He asked me what he could do?

I chucked the action up just as if I was going to true the threads and face. I bored out the bad threads and then established a 20 tpi. It came out pretty nice.

I even made him a gage for the thread, but told him that this thing was now totally oddball, and be thankful I was able save it.

Then he turns around a month ago and tries to sell it. Needless to say, not many wanted it.

So my best friend offered him a very reasonable price, knowing I could install barrels in it, and knowing since I did the fix, it would be fine.

Needless to say, I will no longer do any favors for this shooter. I did it for him so he would at least have a serviceable action. He returned the favor by trying to make a buck.
 
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I wonder if freezing the barreled action and wrenching while as cold as possible might work. The two steels might contract a bit differently, and they should actually get a little less gummy.
 
Galling is caused by local high pressure points on susceptible steels. Fortunately the 400 series steels used on barrels and actions are mildly susceptible. If we used 300 series steel galling would be much more common. So one way to gall is to tighten way too tight so that the pressure between the surfaces goes up too high (10,000 psi is normally used as a rule of thumb). More likely what happens is a local area such as a dinged thread or a mismatched thread or a high top on either the male or female threads makes hard contact and is forced to deform to allow threading to move forward. Since the surface area of these imperfections is very low, it takes very little force to reach the galling threshold (pressure = force / area).

So galling can almost always be avoided on barrels with a few rules.

1. Always use a nickel based antiseize. This helps a lot. If you don't use one you can still be successful but I use one.

2. Your barrel should thread easily by hand down to the shoulder and then tighten up with less than 1/4 turn. If it doesn't, you have a burr or some other problem that must be fixed before threading on.

3. When cutting threads, always make the major diameter a toward the bottom of the spec. for example on 1.060 x 16 threads I turn the major diameter down to 1.058. this ensures the crown of the thread doesn't hit the bottom of the female thread. It is possible to have a poor female thread in a mass produced action causing contact in this area. If you do, that action would be a good candidate for truing.

4. The tendency of most machinists is to make threads too tight. loose is always better than tight.
 
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carlsbad said:
Galling is caused by local high pressure points on susceptible steels. Fortunately the 400 series steels used on barrels and actions are mildly susceptible. If we used 300 series steel galling would be much more common. So one way to gall is to tighten way too tight so that the pressure between the surfaces goes up too high (10,000 psi is normally used as a rule of thumb). More likely what happens is a local area such as a dinged thread or a mismatched thread or a high top on either the male or female threads makes hard contact and is forced to deform to allow threading to move forward. Since the surface area of these imperfections is very low, it takes very little force to reach the galling threshold (pressure = force / area).

So galling can almost always be avoided on barrels with a few rules.

1. Always use a nickel based antiseize. This helps a lot. If you don't use one you can still be successful but I use one.

2. Your barrel should thread easily by hand down to the shoulder and then tighten up with less than 1/4 turn. If it doesn't, you have a burr or some other problem that must be fixed before threading on.

3. When cutting threads, always make the major diameter a toward the bottom of the spec. for example on 1.060 x 16 threads I turn the major diameter down to 1.058. this ensures the crown of the thread doesn't hit the bottom of the female thread. It is possible to have a poor female thread in a mass produced action causing contact in this area. If you do, that action would be a good candidate for truing.

4. The tendency of most machinists is to make threads too tight. loose is always better than tight.
Click to expand...

..002 to .003 clearance on the pitch diameter is about right.
 
carlsbad said:
2. Your barrel should thread easily by hand down to the shoulder and then tighten up with less than 1/4 turn. If it doesn't, you have a burr or some other problem that must be fixed before threading on.
Click to expand...
Interesting point,I have never had a barrel turn a 1/4 inch beyond that point let alone 1/4 turn .That would scare the poop out of me !
 
338 Mollett said:
Interesting point,I have never had a barrel turn a 1/4 inch beyond that point let alone 1/4 turn .That would scare the poop out of me !
Click to expand...

If it keeps turning, and yes, 1/4" circumference is probably closer than 1/4 turn, then you don't have a good fit and all that turning is going into moving metal around.
 
Any of you ever tried this product? I’ve been using it for years and never had problems. I really like it. 3FFAF5D2-3082-4657-A758-B6F4FE2D5D4A.jpeg
 
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