Thread Locker Fails

thread locker

Large Wall Sculptures require a reliable threadlocker

Thread Locker Study

Thread locker generally comes in a very small tube and seems very expensive for the quantity I am buying. But I had been feeling like I needed plenty on hand, so I had been constantly adding to my collection.

Thread locker is usually very low in viscosity, so I had high hopes when I bought a stick of Loctite 248 medium strength blue from Enco last year. It was like a small tube of blue speed-stick deodorant and didn’t run at all. I tried applying it to one side of some 5/8″ bolts, thinking that the nut would spread it around. When I went to remove the nuts a week later, it seemed to have not done any thread locking at all. Perhaps that was because the nut hadn’t spread out the thread locker. So I tried it again, applying it completely around the bolt. 5 days later, nothing again.

I regularly use a thread locker when I assemble my multi-layered wall sculptures with 1/4-20 nuts and bolts. Each piece has a patina that needs to extend beneath its overlying piece. I can’t weld these pieces together because a) then I wouldn’t be able to get them apart b) the welding heat can cause delamination of the copper or discoloration of the patina and c) it would be difficult to incorporate spacers with a welding technique. I usually have at least 1/2″ between layers – a very cool visual effect.

So I was dismayed to hear that some of the 1/4-20 nuts with a red (permanent) thread locker had come loose on a wall sculpture that I’d shipped to California. True, it was 3 days constantly vibrating in the back of a truck – I would come loose too. But still, the nuts should have held.

Thread Locker Tests

Like many people, I tend to believe what companies tell us about their products. It pays to be skeptical, but it takes so much time to do testing, that sometimes I skip it. However, this seemed to be an emergency, so I made the extra effort to test my thread lockers. Here is the test I ran, in tabular form.

Thread Locker Name Cure Time inch-pounds to loosen
Loctite Blue 242 30 days less than 5
Prime Lok Blue 245 30 days less than 5
Loctite Blue 248 30 days less than 5
Permatex High Strength Red 30 days less than 15
Permatex High Strength Red 2 days less than 20
Loctite High Strength Red 271 30 days less than 20
Loctite High Strength Red 271 2 days less than 20
Loctite Medium Strength 242 30 days less than 2
Loctite Medium Strength 242 2 days less than 8
Permatex Pentrating Green 30 days less than 2
Amazing Goop – Household 2 days less than 2
Smart Coat 1K – clear coat 2 days less than 1
Loctite Superflex Clear RTV 2 days less than 1
Liquid Nails – Small Projects 2 days less than 2
Gorilla Glue 2 days less than 35
3M epoxy 420 30 days less than 50
3M epoxy 460 30 days less than 60
3M epoxy 110 30 days less than 50
thread locker

Shipping vibration will loosen all the nuts holding a wall sculpture together.

Thread Locker Results Discussion

Surprising results. The first 30-day tests of the red (permanent) thread lockers were so poor that I re-did them with the 2-day test. I don’t know why I got disparate results on two of them. Still, less than 20 inch-pounds is not good enough for my purposes. And to have it work well sometimes and not others is not good.

The best test would probably be a 24 hour and/or 12 hour test. Usually you get the nuts on the wall sculpture on tight and then you want to be able to ship it out the next day.

I included Smart Coat 1K in the test because I have some of this clear coating in a jar and the jar lid is so hard to get off when the coating has dried. But the jar lid is 4″ in diameter – big size difference versus a 1/4-20 nut.

Do these thread lockers get old? I doubt it. Do they separate and have to be shaken before use? I don’t think so – no directions say to shake or stir well first. Do the bolts have to be cleaned with acetone first? I hope not.

My torque wrench is by K-D Tools, #2955, a beam type. I don’t have a calibrator, but it’s new and I hope it’s accurate. Like all beam torque wrenches, it is to zero before using and easy to read.

I now use only 3M epoxy for my thread locker, and paint it all around the bolt. Plus I torque all the nuts to 40 inch-pounds. It takes a little more time, but I am glad to do it for the peace of mind. I may also use Gorilla Glue for less critical applications.

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