Questions regarding experiences with loctite & using 680 or 630 series retaining compounds as thread-lockers

Hi everyone,

Is there anyone in the forum that has used any of the 600 series loctite "retaining compounds" as thread-lockers ?

I have tested some loctite # 262 & #2760 thead-locker on a #10-24 screw with a small pattern hex nut having a height of 7/64". I tried black oxide finished & stainless screws with stainless and brass nuts. After

24 hours, the strength was not satisfactory. Loctite said that the #2760 is some of the strongest thread-locker they make & does not need primer and even works in the presence of a small amount of oil. I did not use primer as loctite said that the primer is already in the #2760 and advised against it's use. The screws were brand new out of the box and appeared clean and dry.

Someone suggested using #680 retaining compound as a threadlocker and said that it should be stronger than threadlockers. I see no reason a retaining compound would not work as a threadlocker unless the gap in the screw threads is too large for the retaining compound to dry properly.

Loctite lists the # 638 retaining compound as "maximum strength" but the # 680 has a shear strength of 4,000.00 PSI

Loctite's technical data sheets don't list the strength of each product in the same way and it makes it very difficult to compare products. They should just list the torque necessary to break the nut loose in each case and provide data for large and small nuts.

This thing never gets hot and is always used at room temperature. I just want to use a threadlocker or retaining compound to permanently lock the nut to the screw with the greatest amount of strength possible. It's no problem to wait 24 hours for the assembly to dry.

Loctite only recommnended using threadlockers, but someone out in the field said they had used the 680 loc-tite as a threadlocker with success.

What loc-tite product will produce the strongest bond and/or the greatest resistance to the nut breaking loose and/or backing off ?

I am going to test some of the 680 and perhaps 638 retaining compound, I just wanted to see if anyone had any experiences they could relate to me that might help me choose the best product for the job. Perhaps a two part epoxy would be stronger, but then I have to mix it and I would rather use a single part product already mixed.

Thanks for your help. John

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I haven't used the newer high-strength Loctites, although I used to keep 600 handy for high-torque locking, and it always worked well for me.

Regarding epoxy, you may be interested to know that industrial applications of thread-locking epoxy include (or included: I reported on it 25 years ago) some stuff made for the purpose that was encapsulated in little hollow phenolic beads. You'd mix the beads of epoxy and hardeners together and stick them to the threads of the fastener with some lacquer-like coating. Then you put them on the shelf until you needed them. When it came time to assemble the threads with whatever, running them into the nut (or whatever) would break the beads and mix the epoxy and hardener together.

Neat. Strong. Melts in the threads, not in your hand...

-- Ed Huntress

Reply to
Ed Huntress

I have used 270,272,620,680...and the biggest problem you have is that stainless is just to passive. You must use primer N or T. You will have to assemble real fast before the loctite sets up especially the thicker retaining compounds. The brass is no problem. Its very active and two brass parts with this stuff is almost impossible to take apart.

Reply to

are you tightening the nuts down against something or just testing on a

bolt with a nut threaded on it at random ? the fasteners still need to be torqued correctly as the loctite needs the anaerobic enviroment to cure properly.

if you need vibration resistance for a installed fastener that does not get torqued completely , as in fasteners on aluminum motorcycle parts and race cars , there is a reason for lockwire , nylon locknuts

that being said , red 272, 262 loctite assembled on 1 7/8 - 12 hydraulic cylinder rods will strip the threads off the rod before coming loose , unless heated to 450 degrees to break the bond .

John2005 wrote:

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Brass is NOT very active. I had a problem with brass and eMailed Loctite. They gave me that answer and it is my experience.


Reply to
Nick Mueller

Then you got bad information from who ever answered that email because it is 100% wrong. And you experience is very limited. I know it is wrong from attending past Loctite seminars, reading literature, and having used and tested anerobics in product design for the past 30 years. You may also want to send the some of these links to your technical adviser at Loctite. The first one comes from the company he works for.

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Hi everyone,

Thanks for your replies.

C henry, when I tested, I just ran the nut on the screw at random and did not tighten it down. I had wondered if the nut had to be tightened down a little to get more strength.

In my application, due to the way the nut is being used, I will not be able to tighten the nut down very much at all. I will have to just snug it down so that it takes up axial play, but I cannot tighten it down very tight & I'm almost sure it won't meet any type of torque down specs.

Perhaps tightening the nut down will seal off the threads and keep more air out, but it seems the air would be sealed out in any event. Just running the nut down on a screw at random and not torquing it down, the loctite still dried after 24 hours. If I snug the nut down a little, perhaps the loc-tite will dry a little better.

I can't use a locknut because they don't make one that is small enough (the height is too high). I tested some "top lock" nuts from Mcmaster carr but they did not work well in this application. I would want to have something stronger than the average lock-nut anyway.

As far as brass is concerned, loctite told me that brass was an active material and would produce a better bond than stainless (at least when using the #2760 loctite). Whether a material is active or how well it works may depend on which loctite you use.

In my tests, # 262 with no primer on a black oxide screw with a brass nut produced the strongest bond, even stronger than the # 2760 loctite with various combinations of stainless, black oxide, and brass screws and nuts. However, the # 262 without one component being brass, did not do as well as the # 2760.

Loctite also told me that only one component (either nut or screw) needs to be an active material.

I'm not very confident in the responses I get from loctite because it seems what answer you get depends on who you talk to. You would think a larger company like that would have more hard test data on various material and size combinations.

Thanks aga> Nick Mueller wrote:

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You do not have to tighten the nut to exclude air. The presence of the loctite creates an air seal in the gap between the thread form and that is what creates the cure. You can see this effect before you toss expired loctite. Squeeze all the air out of the bottle and wait a few months. It starts to harden inside the bottle. For a real strong bond it takes more then just one active part when the other part is as passive as stainless steel, especially a precipitating hardening type.

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OK, then he is an idiot.

OK, then I'm an idiot observing failures whenever I used brass.

Then you made that simple experiment: Loctite two strips of steel and two strips of brass. Try to pull them apart after 10 minutes. Repeat with 1 hour etc. You can see by yourself which one has strength and which one not. Maybe just our definitions of "active" differ.

No need for that. I eMailed them _after_ I found that it doesn't work. I just got a confirmation for my experience.

If you look at the data sheet for 603, you will notice big differences in settling time and strength between steel and alumin(i)um. They didn't list copper alloys. Also note, that the graph shows steel-Al and does _not_ show Al-Al. I guess it will be even worse.

Regarding Hernon: They even aren't ashamed to violate Loctite's copyright. That page is a simple copy of Loctite.


Reply to
Nick Mueller

It is not my definition, read the linked page from Loctite. In black and white, plain as day, it is Loctite who calls brass active.

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Paper is patient.


Reply to
Nick Mueller

Loctite use a number of anaerobic adhesive families. Some work better on a given material than others. Stainless steel tends to be one of the more difficult materials, both in cure time and in bond strength. Copper containing alloys frequently cure faster than carbon steels, but may have lower final strengths. It is very important to consider a range of products or even ask Henkel/Loctite if large amounts of money are involved in the product. A case-in-point for comparison would be, for instance, 973 against 603 very similar strengths, but 973 initially cures three times faster on brass than on steel and achieves 90% of the same final strength.

Lots of products, not all the same :-)

Mark Rand (just stirring things) RTFM

Reply to
Mark Rand

Try 271. It's always worked for me.

Reply to
Don Foreman

Hi everyone,

I tested some 270, 271, 262, 2760, 638, & 680 loctite as a threadlocker on some 10-24 and

10-32 screws & nuts. Whether the thread was course or fine seemed to make no significant difference as far as strength.

I tested with and without primer using black oxide finished screws and zinc, brass, and stainless nuts. The stainless nuts had the weakest bonding, and the brass nuts seemed to have the strongest bonding although the zinc seemed close. I let the loctite dry for exactly 24 hours.

The best bond seemed to be the 680 using a brass nut, black oxide finished steel screw, and 7471 primer. I think it will be plenty strong for my application, but it did not destroy the threads when taking the nut off the screw, as a couple people told me it would. The 271 was also good, but I think the 680 was a little better, and it seemed to dry faster than the

271 using the brass nut.

The 2760 does not seem very strong at all on small screws.

I just thought I would report my findings to you in case anyone was interested.


D> >

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Thanks for providing some real world results.

Reply to
F. George McDuffee

F. George McDuffee wrote in article ...

Statements such as.......

"...seemed to make no significant difference "

"...the brass nuts seemed to have the strongest bonding although the zinc seemed close."

"The best bond seemed to be the 680..."

"I think it will be plenty strong for my application, ..."

"The 271 was also good, but I think the 680 was a little better,... "

" seemed to dry faster..."

"....does not seem very strong at all on small screws...."

Are hardly objective, technical "real world" results.

They are one man's opinions on his own particular results, or so it "seems."

Anybody else could easily have completely opposite results under differing conditions.

The fact that one "seemed to be" stronger than the other is subjective.....NOT objective results.

How much torque did each require to break the bond? THAT would be objective, "real world" results.

Thew only exacting standard used seemed to be the 24-hour drying time......

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Perhaps, but his shared experience is certainly more interesting than your criticism of his report.

Reply to
Don Foreman

Perhaps I did use the word "seemed" too much when explaining the results of my tests. The 680 was noticably stronger than all other numbers, except for the 271, which was close but not quite as strong as the 680. The best bond occurred when using # 680 on a black oxide finished screw with a brass nut & 7471 primer on both the nut and screw.

I did not need a torque wrench to tell the difference, and if a torque wrench were needed to tell the difference, the difference would be insignificant anyway.

I did not mean to imply that my results would be the same for everyone, or that I conducted a controlled laboratory experiment, I just wanted to report what worked for me in case it could be of interest or help to anyone else.

As far as being subjective, since life is relevant to the perceiver, everything is subjective.

Controlled laboratory experiments are subjective due to variances in equipment accuracy and reliability, the skill, reliability, and personal motives of the person conducting the tests, & human and mechanical error. This is the "real world"

Take care, John


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