loctite on barrel threads
I have seen people use loctite both on barrel threads and also to secure parts that are press fit together. does anyone know how long a part secured with loctite can be expected to hold together, and if any conditions, other than heat would cause it to fail? There's a wierd purist in me that thinks that if you need it to do the job, you are doing something wrong, but sometimes modern methods and materials are pretty amazing. some of the loctite products that I have seen can fill gaps up to .015", which is a pretty sloppy fitup. Wondering if the repeated rattling and shaking and pressures involved near the chamber would work this stuff loose? silverbrazing seems more permanent for a press fit, but has its own flaws, such as the possibility of warping the barrel, and destroying any heat treating that was done to the reciever.
Funny, I have done it and my only worry is will anyone ever be able to get it apart again. Properly used it will hold very well. Sometimes too well. But then again there are different grades for different uses.
I'm a bit weird, but I don't like plastic parts on my guns, either. I have some that are well over 100 years old and shoot fine, but they are made of wood and steel and (sometimes brass). I have not seen a 50 year old piece of plastic that was worth a damn. but then plastics and adhesives have come a long way, even in the last 20 years.
Originally Posted by anchorman
In my experience I found that locktite isn't needed on threads, contrarily, I always put a thin coat of anti-seize on them instead...I haven't come across a barrel yet that was "easily" spun off. A press fit could be a different story but rather than loc-titing it I would secure it with a cross pin and not depend on an epoxy.
Someone I know that does all his own rifles for long range shooting and is machinist by trade told me he just puts a drop of nail polish on the thread for a barrel, does the job and apparently easier to get back apart.
Loctite on a true press fit is not doing anything. If its actually press fit the loctite will be squeezed out. What it does is take up any space that is not a true press fit. For instance you press a pin in a worn hole. The loctite will replace the portion of the bore that is worn. This will keep the pin from flexing and working loose.
There are many different grades, and types. Even in threads, I see it as something that takes up the empty space to prevent flexing of the two parts.
As far as thread loctite I cant say ive personally ever seen it fail. I worked on round balers for several years. All the 3/4 bolts that held the rollers in had lockwashers and red Loctite. If they didnt have loctite they quite often worked loose. Even with lock washers.
Alot of the time when they were assembled correctly it would require the bolt being red hot before removal with an impact.
On a barrel, if the threads are cut correctly, I personally dont see any reason for it. I dont see that there would be enough stress on the joint to make it neccesary. If the threads were "buggered up" at all then I think it would be a good idea.
Some of the single shot target rifle smiths recommend fitting the barrel up a bit more than hand tight and then use blue thread locker in the final assembly. I don't recall the exact reasoning, but something about not inducing additional stress to the barrel. I do know that most of these guns are sub MOA with plain base cast bullets. I've done this on some old Winchester lever guns as most of these I have run into don't have the barrels cinched up very tight at all. None have come loose in use, but are not hard to disassemble if necessary.
I once fit an over-indexed barrel to a M1A receiver and used red loctite. Shot a NMC season with it and she stayed put. Didnt come loose till I put the propane torch to it. I usually fit Krieger M16 barrel extensions to within a few degrees of TDC and set them with red also. No need for the 180 pounds of torque. No stress, they shoot well enough to win a match or three, and they dont come off untill I want them to.
Thread locker has it's place, and it covers up a few sins, too.
Perhaps this has something to do with some barrels having a crush fit on the screw threads that would deform the chamber dimensions? Whatever I do now, I want to maximize potential accuracy of the gun, lord knows I'm not yet the best marksman out there by a long shot. I'm expecting magic, but I'd be happy if I could hit consistent 2" groups from a bench rest at 100 yds. I wouldnt complain if the gun or I shot better than that, but You've gotta start somewhere.
Originally Posted by clippermaniac
I have removed a few M700 barrels with some sort of loctite on the factory barrels.
I have never put locktite on barrel threads, I was taught at TSJC to crush fit .002 barrels.
The .002 is figured in the chamber or I hand ream the last .050 "
One benefit to the loctite (remington seems to use it from the factory) is that many people LOVE to slop bore cleaner up into the receiver ring, some of that bore cleaner is a aqueous solution (Hoppes elite as one example) that has a history of causing rust when it gets into places like the barrel tenon thread.
good point! I don't use stuff like that, but if I were shooting corrosive ammo, which I might with this project, I would probably use water and or ammonia to wash out the barrel.
Originally Posted by willbird
Well a machinist that came to work with me as a gunsmithing apprentice had a saying. If you can't hit a size, give them a bullshit finish and it will probably sneak through. I guess the same can be said for Loctite and threads. In truth, I guess it is one of the few man made products that actually works BETTER than advertised and I have made a lot of money drilling out Loctited screws with ruined heads over the years.
If torquing a barrel thread to 150 lb.ft. would crush the threads or deform chamber dimensions, then scrap that barrel, because the barrel is more lead than steel. Assuming that the average size thread on a rifle barrel is 1", then 150 lb.ft. is well below the torque limit for that size thread by at least one half.
Perhaps this has something to do with some barrels having a crush fit on the screw threads that would deform the chamber dimensions?
Loctite, Yes, I use it on barrel threads (only a drop - as per instructions) and I don't have sloppy or ill fitting threads. I also use it on the inside of scope rings of heavy or sharp recoiling rifles to prevent slippage. I use Loctite products for several different applications and find them to be very useful when used as per the recommendations set forth by Loctite.
Just my 2¢..........
NRA Life Member 1976
I just pulled some that looked like they had more $$ in thread locker than the barrel was worth.
Originally Posted by MilGunsmith
Neverseize, yes, threadlocker not much point. The right hand twist in most barrels induces a torqueing action that keeps the barrel from loosening. Goat
I designed heavy equipment for years.
We use a lot of loctite products in assembly.
They work well when properly selected and applied to the righ application.
Things that break thread lockers down -
Vibration and shock loads
I dont usualy like to use thread lockers on guns. The screws are small enough your likely to bugger the heads getting a loctited one out, and the shock loads from fireing that loosen barrels and scope mounts will do it with or without loctite. Take a look at "Rifle Accuracy Facts" the autor tested thread lockers on barrel joints and was not satisfied.
Loctite tends to leave a lot of goop behind in a hole and on threads, so a lot of clean up is required before reassembly. Chasing small holes over and over again with a tap is asking for loose fits. Wire brushing fine threads tends to remove blueing. Both are not desireable on a firearm.
Loctite should be used when necessary to secure joints that dont require any kind of regular operation.
It should not be used to correct improfections in machine work.
Also, loctite is a lubricant when it is applied. The same torque values will allow the screws to clamp down harder (or strip) when they are lubircated.
As a millwright the proper tensioning of threaded fasteners is part of my job. So what is this "crush"? Is this some magic term to sound technical? If I "crushed" a fastener I would have a mess.
People talk about some magic "crush" value they get when they tighten a barrel into the action. I have heard .002 quoted a lot. Now I do not tighten barrels super tight, but I have never been able to measure any "crush", if I set one up with .002 endplay on a go gauge in the lathe with the barrel run snug by hand, when I later tighten it and check again, well I still have .002. Maybe there is something in the water around here :-). I do understand that bolts DO stretch, there was a fad for awile torquing engine rod bolts by measuring the stretch not the torque on the nut, probably a good idea.
Originally Posted by tdmidget
On PCD inserted milling cutters we had some issues with the screws that hold the inserts in/on coming loose, so I used Loctite medium strength for the proper screw dia on them, never had to do any major cleanup or tapping of holes each time I replaced inserts, and the stuff sealed the threaded joint from stuff that might rust the screw threads.
The loctite line of products has either matured a great deal in the last 30 years I have been around it, OR they do a better job if letting the end buyer know of all the things they make, back in the 70's all we knew of were "blue" (medium strength) and "red" (requires heat to remove).
Some of the general ignorance out there now is not knowing that the "strength" of the loctite correlates to the fastener dia, and that cleaning and or priming makes it work a lot better. Loctite MAY also prevent galvanic corrosion between say aluminum and steel ??