I see that's an actual glue. Most of the missing screws that have come my way have been on older firearms and you could make the case that that's because machining wasn't as precise in the old days, so maybe his guns are as old as he is?
A frank, open, and honest discussion of threadlocking products.
- Thread starter Big Bad
- Start date
I see that's an actual glue. Most of the missing screws that have come my way have been on older firearms and you could make the case that that's because machining wasn't as precise in the old days, so maybe his guns are as old as he is?
The fine print on the Permatex products says they're only good for 1/4" bolts and larger, so might be risky on scope screws and other tiny stuff we use. Maybe Loctite Purple would be the most appropriate thing to track down?
Been using it ten years. For the panicy types I will add, I have never, ever had a problem getting things apart again, even after 4 or 5 years. If you know how to properly use tools, and use the correct tool, comes apart every time.
I've successfully applied blue Loctite to constantly loosening screws on eyeglasses, for instance, so I have every confidence it's good for any threaded screw as small as those and up. OTOH, blue is what I've always kept around, or tried to, and I'm pretty sure any colour would work just as well, just want to play the percentages based on the official recommendations.
burnt_servo
CGN Ultra frequent flyer
- Location
- right in the middle of b.c.
nope that is with ALL loctite ....
the strength is proportional ..... if you use the blue stuff on a small enough part , the bond will be stronger that the part itself , causing the metal to actually break ..... throw a small amount of heat at it , the Loctite releases and the part can now come apart ....
huge upside to loctite is it keeps the threads from corroding and actually acts sort of like a lubricant when heated , actually helping the part to be removed .
You dont need heat to remove blue locktited scope mount screws. I never use it on ring screws they are exposed for retightening anyway after firing a few rounds. Bases need to stay tight from first installation, locktite blue does the job excellent stuff
- Location
- Steel Town
All I can on this matter is that red loctite is extremely strong, and will likely require heat to remove. Using VERY small quantities on small screws will ensure an unbreakable bond under normal use.
Understood, it's why I play it safe with the blue version.
And on the posts about the eyeglasses I've been wishing I mentioned that it was not screws in plastic. Loctite will dissolve plastic- I've seen it happen.
Used properly Loctite or similar works in more than one way. The corrosion protection within the threads is one important point, another is the anti galling effect or lube effect especially when using stainless to stainless connections. Marine grade stainless screws can be a ba stard. In one engineering company that I worked for almost 35 years ago the owner made sure every screw had to have loctite on it, reason was because it seemed just about impossible to get trained mechanics to tighten screws properly. These were professionals not hobby guys. After a large machine fell apart in use (automation machinery for the car industry) the boss had enough.
One should remember to adjust torque when fitting screws with loctite. In our rifle stock manufacturing now we use loctite on almost every screw. One place I don't use loctite on are the action screws as I like to check torque on these. Screws that clamp things and are open /closed frequently we use waterproof grease as a lube.
edi
One should remember to adjust torque when fitting screws with loctite. In our rifle stock manufacturing now we use loctite on almost every screw. One place I don't use loctite on are the action screws as I like to check torque on these. Screws that clamp things and are open /closed frequently we use waterproof grease as a lube.
edi
The products has its uses (including very limited use on firearms). I just installed a rail (EGW) on a revolver and right in the instructions it stated they recommend blue thread locker and torque to 20 inch pounds. If something comes loose on a firearm, who fault is it? The gunsmith that put it all together or the guy that owns and uses it? I surprised how many people don't own and use a inch-pound torque wench when working on their firearms. To each their own.
- Location
- Southern Vancouver Island
Right ye be on those points. I'm even more surprised at folks that get a proper torque wrench and then use 'em wrong. I.E. Using them to loosen a fastener which will damage the tool. Other things being, not setting the adjustment back to zero after use which can cause the spring in the tool to take a set & give lighter readings if left for long periods on higher settings. Keeping the wrench clean, lubed & stored in a dry space be the way to go.
I have 30+ years of reliable use on my one.
Attachments
Do you happen to know if any research has been done with some of the advanced polymers (Magpul, Benelli, etc.)? Makes me wonder about some of the screws I’ve used it on where excess may “bleed out” and come in contact with the polymer lol.
I find the screwdriver format to be handier. Wheeler makes this one plus a pricier digital display model. I have however seen very few firearms or accessories that give recommended torque amounts.
Rayleigh_Scattering
Regular
- Location
- Under the arch
Physics lesson!
A bolt works just like a C-clamp (with a really skinny C).
Picture a couple of 2x4's that have been C-clamped together at their ends.
If you try to shear the joint between them (by trying to pivot it) it is the friction of the wood faces that resists. The loading on the C-clamp doesn't change until you pry so hard that the friction joint slips (at which point it won't help much).
If you try to push the wooden faces closer together the loading on the C-clamp doesn't change at all until you crush the wood.
If you try to pull the wooden faces apart the loading on the C-clamp only changes (significantly) once the pull force is higher than it's clamping load. Until then all you're doing is decompressing the wood joint.
The concept of knowing when "load change" on the C-clamp happens is key because bolts are stretchy.
Picture a nut and bolt assembly but instead of steel they are made of rubber.
When I torque them up the bolt is in tension and the nut is in compression. So the bolt gets stretched longer and the nut gets squashed shorter. But, you also know from experience that when stretched rubber gets thinner, and when squashed it gets wider. So the threads of the nut expand outwards while the threads of the bolt shrink inwards.
When the bolt was originally torqued up that isn't a problem (well, it is actually, but its one we know how to deal with) but consider what happens if the load on the bolt changes in service.
Every time the tension on the bolt increases the bolt shrinks in a bit more and the nut spreads out a bit more. Every time the tension on the bolt decreases the bolt grows back out and the nut shrinks back in. They can't both change shape together, so once the differential force from grow/shrink gets high enough the joint faces of the thread slide on each other. In a bit, out a bit, with every change in tension large enough to break the thread face friction.
And every time they slide a bit radially they also have the opportunity to slide back a bit along the thread incline. Because once a friction joint starts to slip (like fishtailing your motorbike) it stops being directional and is free to move from even small off-axis loads.
The name of the game in bolted joint design is to prevent the load on the bolt changing enough for the differential movement to overcome the thread face friction, because once it changes enough to do that the thread will start to move and loosen up.
If the bolts are big enough and torqued correctly then the clamping force is high and all loads and load changes are borne by the surfaces of the clamped joint. The tension in the bolt never changes significantly, nothing moves, and the joint survives (basically) forever with no thread locking chemicals/fittings being required. This is what we call a well-engineered joint, and your car is full of them.
If the bolts are under-sized or under-torqued the joint will slip or separate and the loading in the bolt will vary, and the stretch-wiggle dance will start to loosen the thread. Once the thread starts to loosen clamping force drops further and the process self-accelerates. You'll have seen this yourself; bolts that last for years but then go from "Looked fine yesterday" to rattling loose in a short time.
Gluing* the nut onto the bolt will prevent it from loosening, but it is a workaround that doesn't solve the underlying problem of the joint or how it was assembled.
Now, there may be times when a workaround is warranted. A joint where a big-enough bolt won't fit or torque can't be controlled and I'm OK with it moving a bit occasionally, or when a loose bolt is a much smaller problem than a missing bolt (like a wheel hub nut), or when occasional combined shock/temperature loading is too high for friction to resist and other features (like pins) are locating the joint, or when minimizing unsprung mass is critical.
Your car will have a handful of places where this is done, but not many.
Or maybe the chassis are already fielded and reports come back of an under-sized screw working its way loose. A bulletin telling the techs to glue that screw in will be cheaper than a recall.
But now you have to deal with the thread locker. And it being expired (1 year shelf life? Seriously?). And it migrating or outgassing to other surfaces of the assembly (its absolute poison for optical assemblies). And it not being cleaned out properly during re-work. And chemical toxicity issues (loctite is a sensitizing skin toxin).
Going back to the c-clamp example. Epoxying the threads on the c-clamps will prevent them from loosening when the boards move, but it is not the preferred answer. Driving a couple of nails through the boards too will prevent them from twisting, but is not the preferred answer. The preferred answer is "Get bigger C-clamps, locate them correctly, tighten them good and hard and the boards won't move."
I think the above ties together a bunch of previous postings.
-Well-engineered joints don't need locking elements/chemicals.
-Loctite kills warranty on optics
-Torque control is critical for reliable joints.
I skipped talking about stiffness ratios, which explains why short-fat bolts don't stay torqued as well as long-thin ones, but that's a tough subject to crack in a non-technical briefing. I skipped talking about nut/bolt behaviour in shear failure because by that point you've already lost.
*loctite is a single component thermoset glue who's hardening is catalyzed by active metal but is inhibited by oxygen. Put it into a thin deep gap between metal parts, rub those parts together hard to scrape off the oxide layer, and it will harden.
A bolt works just like a C-clamp (with a really skinny C).
Picture a couple of 2x4's that have been C-clamped together at their ends.
If you try to shear the joint between them (by trying to pivot it) it is the friction of the wood faces that resists. The loading on the C-clamp doesn't change until you pry so hard that the friction joint slips (at which point it won't help much).
If you try to push the wooden faces closer together the loading on the C-clamp doesn't change at all until you crush the wood.
If you try to pull the wooden faces apart the loading on the C-clamp only changes (significantly) once the pull force is higher than it's clamping load. Until then all you're doing is decompressing the wood joint.
The concept of knowing when "load change" on the C-clamp happens is key because bolts are stretchy.
Picture a nut and bolt assembly but instead of steel they are made of rubber.
When I torque them up the bolt is in tension and the nut is in compression. So the bolt gets stretched longer and the nut gets squashed shorter. But, you also know from experience that when stretched rubber gets thinner, and when squashed it gets wider. So the threads of the nut expand outwards while the threads of the bolt shrink inwards.
When the bolt was originally torqued up that isn't a problem (well, it is actually, but its one we know how to deal with) but consider what happens if the load on the bolt changes in service.
Every time the tension on the bolt increases the bolt shrinks in a bit more and the nut spreads out a bit more. Every time the tension on the bolt decreases the bolt grows back out and the nut shrinks back in. They can't both change shape together, so once the differential force from grow/shrink gets high enough the joint faces of the thread slide on each other. In a bit, out a bit, with every change in tension large enough to break the thread face friction.
And every time they slide a bit radially they also have the opportunity to slide back a bit along the thread incline. Because once a friction joint starts to slip (like fishtailing your motorbike) it stops being directional and is free to move from even small off-axis loads.
The name of the game in bolted joint design is to prevent the load on the bolt changing enough for the differential movement to overcome the thread face friction, because once it changes enough to do that the thread will start to move and loosen up.
If the bolts are big enough and torqued correctly then the clamping force is high and all loads and load changes are borne by the surfaces of the clamped joint. The tension in the bolt never changes significantly, nothing moves, and the joint survives (basically) forever with no thread locking chemicals/fittings being required. This is what we call a well-engineered joint, and your car is full of them.
If the bolts are under-sized or under-torqued the joint will slip or separate and the loading in the bolt will vary, and the stretch-wiggle dance will start to loosen the thread. Once the thread starts to loosen clamping force drops further and the process self-accelerates. You'll have seen this yourself; bolts that last for years but then go from "Looked fine yesterday" to rattling loose in a short time.
Gluing* the nut onto the bolt will prevent it from loosening, but it is a workaround that doesn't solve the underlying problem of the joint or how it was assembled.
Now, there may be times when a workaround is warranted. A joint where a big-enough bolt won't fit or torque can't be controlled and I'm OK with it moving a bit occasionally, or when a loose bolt is a much smaller problem than a missing bolt (like a wheel hub nut), or when occasional combined shock/temperature loading is too high for friction to resist and other features (like pins) are locating the joint, or when minimizing unsprung mass is critical.
Your car will have a handful of places where this is done, but not many.
Or maybe the chassis are already fielded and reports come back of an under-sized screw working its way loose. A bulletin telling the techs to glue that screw in will be cheaper than a recall.
But now you have to deal with the thread locker. And it being expired (1 year shelf life? Seriously?). And it migrating or outgassing to other surfaces of the assembly (its absolute poison for optical assemblies). And it not being cleaned out properly during re-work. And chemical toxicity issues (loctite is a sensitizing skin toxin).
Going back to the c-clamp example. Epoxying the threads on the c-clamps will prevent them from loosening when the boards move, but it is not the preferred answer. Driving a couple of nails through the boards too will prevent them from twisting, but is not the preferred answer. The preferred answer is "Get bigger C-clamps, locate them correctly, tighten them good and hard and the boards won't move."
I think the above ties together a bunch of previous postings.
-Well-engineered joints don't need locking elements/chemicals.
-Loctite kills warranty on optics
-Torque control is critical for reliable joints.
I skipped talking about stiffness ratios, which explains why short-fat bolts don't stay torqued as well as long-thin ones, but that's a tough subject to crack in a non-technical briefing. I skipped talking about nut/bolt behaviour in shear failure because by that point you've already lost.
*loctite is a single component thermoset glue who's hardening is catalyzed by active metal but is inhibited by oxygen. Put it into a thin deep gap between metal parts, rub those parts together hard to scrape off the oxide layer, and it will harden.
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And that is all that is really needed for 99% of the job it is asked of.
Now, if you are serious about thread lockers talk to a Harley Owner and they will swear by the Red stuff.
Then ask their mechanic and they will tell you all that is needed for 99.99% of what the Hog owner needs to sue is the Blue stuff.
A little dab will do you.
Rob
I might even question the quality of the screws used these days as to the number that may be sourced out of China. Early 80's saw an influx of cheap Chinese bolts into N.A., and a bunch of issues with them stretching and shearing, NTSB had to issue a warning to mfgrs about them as they'd caused accidents, like a fifth wheel coming off the frame. I wonder at the procurement sources for them these days, could easily be some crap screws around. With some small screws sometimes Loctite 242 can be too much for them, the 222 purple is better suited to small stuff. I had an M4 screw on a red dot mount get extremely obstinate with the 242 blue on it. Gunsmith put it on there when he made me a mount for it. Loctite can cause issues in aluminum as well.
Rayleigh_Scattering
Regular
- Location
- Under the arch
Easy test for suspect bolts:
We usually spec the torque on bolts to load them between 2/3 and 3/4 of their breaking strength at install.
So, take a dozen of the mystery bolts and torque them into a piece of scrap plate until they break.
If they all break at a fairly consistent torque somewhere above 1.3x the torque spec you probably have (12 less) good bolts.
If there is a large scatter, or if any break at less than 1.3x the torque spec you might want to think twice before using these for anything important.
Thinking about it, this might be a good learning experience for one of the coop students.
We usually spec the torque on bolts to load them between 2/3 and 3/4 of their breaking strength at install.
So, take a dozen of the mystery bolts and torque them into a piece of scrap plate until they break.
If they all break at a fairly consistent torque somewhere above 1.3x the torque spec you probably have (12 less) good bolts.
If there is a large scatter, or if any break at less than 1.3x the torque spec you might want to think twice before using these for anything important.
Thinking about it, this might be a good learning experience for one of the coop students.
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