Threadlockers and superglue

I have never used threadlockers before (but I have only recently discovered the benefits of internal combustion engine, so forgive me!).

I spent some considerable time on the various web-sites and got only limited answers to my questions. Here they are, I would be grateful for any advice:

1) How does a $14-threadlocker differ from a $2 Superglue? I gather the threadlockers are anaerobic. Does that mean that superglue is aerobic? 2) How long does it take for a threadlocker (say Loctite 242) to cure? 3) The purple, blue and red are different strengths. I just could not get a picture of *how much* they differ. I gather you need heat to loosen up the red, but what about the others? 4) Why the different thread size recommendation? 5) Where does the "Green" threadlocker fit in strength-wise? I understand you put it on a fastener already in place, but what kind of result can be expected?

I just did an experiment: Put a 1/2" nut half-way on a bolt and then dribbled some cheap superglue into the cavity. It took its sweet time curing (as observed by the behaviour of the small droplet in the middle of the cavity), but then I had to grip the bolt in a pipe-vise (ordinary vise would not do) and managed to get the nut off with a 3/4" spanner. On inspection, only about 3 threads were engaged and there was still residue of uncured glue on them.

Thanks for help,

Question 1, a threadlocker gives you some working time for assembly in terms of minutes or more depending on the product, superglue goes off in seconds so I would expect it to start setting before the piece may have been fully assembled.

Question 2, google the likes of "loctite 242", it turns up the technical documents at Henkel IIRC. Like http://65.213.72.112/tds5/docs/242-EN.PDF which probably gives you more information than you wanted to know.

Question 4, from experience it is not a good idea to use a high strength locker on a small thread ~ 3-4mm or less as you may not be able to get it undone as the head or drive such as socket may not be strong enough.

I spent 3 hours yesterday looking for this very page! All I got is MSDS and other waffle! Grrrrr!

Thanks, this is all good stuff I wanted to know.

And a supplementary: Does anyone believe there is a significant difference between threadlockers by different manufacturers (Loctite, Permatex, Safe-t-lok etc. etc.)?

Super glue can be very strong, but it can also be quite brittle. I wouldn't trust it where there a cyclic stresses or vibration.

I think Loctite is now owned by Permatex, so perhaps their products are the same. I have no idea about Saft-t-lok but for routine use I suspect any of the products would be satisfactory. For critical or production use I would think that testing would be advisable.

Don Young

Another problem with threadlockers I just miserably discovered was that they are *lethal* to some plastics. I was trying to assemble some banana jacks with brass nuts on brass posts with plastic standoff bushings for insulation, and the plastic parts literally crumbled after a few minutes from the bit of Loctite 242 that wicked over from the metal. I had different jacks that must have used a different plastic species, because they were OK with the same contact. I see the Loctite sez "not normally recommended for use on plastics", but really, what a weasling warning.

IIRC loctite type products also give a significantly lower strength bond on brass than they do on steel.

Cyanoacrylate (super glue) sets on contact with water vapour in the air (or on your skin, if applied there). It's stored in a container that is sealed to prevent contact with the air.

Threadlockers are weird plastics that remain liquid as long as they are in contact with oxygen. They are stored in bottles that are permeable to oxygen, and which have a significant air space above the liquid. They set only when you isolate them from oxygen, such as in the space between a bolt and nut thread.

Dave

Superglue is cyanoacrylic stuff, cures by exposure to moisture. Generally has a short shelf life even if refrigerated. NOT the same stuff as Loctite threadlockers and cousins. Those are methacrylates that cure by exposure to metal ions and exclusion of oxygen. Packaging is such that there is no metal in it and the bottles/tubes are air-permeable. I've had Loctite be able to cure after sitting for years on the shelf.

Now don't get confused, Loctite also makes/packages cyanoacrylic glues under the Loctite name, but like I said, NOT the same stuff. Cure rate for the threadlockers depends on contamination of the threads involved, grade of threadlocker and size of gap to be filled. Some grades work better than others with wider gaps. Temperature has a lot to do with things, a slow pass over a 100 watt light bulb can speed things up a lot as well as cleaning stuff off with the primer/ accelerator. Some types refuse to cure at all if the gap is too large. Too much oxygen, not enough metal. Best to have grease-free parts and close tolerances.

Stan

Threadlockers won't cure in the presence of oxygen, nor in absence of iron unless a primer is used. So on brass or aluminum they don't cure well without the primer (or accelerator or catalyst or whatever you want to call it. Loctite sells the primer. 7649N or some such number. Loctite 222 is purple low-strength stuff for small fasteners. Smal screws will twist off with stringer threadlockers. 242 is blue and medium strength, and is handy for sealing air line fittings. Sets almost instantly. 262 is high-strength, red. 292 is green and runny for wicking into already-fastened parts. There are a bunch more, like RC680 for retaining bearings and so forth, and another for sealing hydraulic fittings. Forget the number. Go here:

Dan

What would be the best for securely fastening a military Mauser rear sight base that surrounds the barrel? It does not have to be easily removed.

David

no, the above statement about superglue is just plain wrong - it does NOT cure upon contact with moisture in the air - you are thinking of Silicone rubber - I use superglue on woodturning projects (some examples might be seen in the gallery on my web page or at

- and I keep the bottle in my shop, open to the air - the current 1 pint bottle has been there for 3 years and it has not hardened up. What makes it harden up is lack of air and contact with a foreign substance - in particular there is something in the fungus that gets into wood that really catalyzes the reaction - but for sure it isn't moisture.

** Posted from **

Well ... mine was soft soldered in place.

And I think that the repeated (though small) expansion of the barrel during firing will break the joint of any threadlocker like Loctite, which gets rather brittle as it sets up.

Enjoy, DoN.

Silver solder.

Unless you never will fire the rifle. 5 rapid fire shots could cause the barrel to heat enough to break the bond.

Gunner

for cyanoacrylate glue (alpha cyanoacrylate ester) it does indeed get set by contact with moisture.

I dont know what glue you are using but it doesnt sound like cyano. Stealth Pilot

Something is getting misconscrewed here, William. Cyanoacrylate glues ("superglue") are generally moisture-cure, aerobic adhesives. The acrylic adhesives used in the standard varietes of Loctite and competing thread-lockers are acrylic adhesives formulated to be anaerobic-curing.

I don't know if it's possible to make an anaerobic cyanoacrylate, but maybe so. That's not what you buy in the hardware stores, though.

Dave's description is correct. I spent a day at Loctite's headquarters many years ago going over exactly this subject with them, researching a 12-page American Machinist Special Report on adhesive assembly in metalworking. Those little plastic vials that Loctite comes in are porous to oxygen.

-- Ed Huntress

CA glues set by polymerization on their own, not like polymers which set by combining with external stuff (which is why they'll eventually set up in the tube even if kept in zero humidity). Accelerators are available to trigger this polymerization. Mere water is not one of them, and a good thing, too. The instant bonding to skin is not due to water, as any simple experiment will show.

Staking?

The thermal expansion -- or just the mechanical expansion during the moment of firing. It doesn't take much of that to break the bond of Loctite.

Silver solder for a rear sight base soldered to the top surface of the barrel only -- but My 8mm Mauser had the rear sight base as part of a sleeve which fit around the whole barrel, and it was attached with soft solder -- since I was able to heat it enough to slide it off with a propane torch and little difficulty.

Enjoy, DoN.