Loctite, where to use or avoid

[Raul-02]

I have used a high strength thread locker on engine cylinder studs.

I'd be concerned about the ability (down the road) of being able to do a rebuild. I don't have the capacity of heating an entire engine block to 600+ degrees F and then ramping it down slowly which is what one would need to do to avoid cracking the block. Localized heat runs a very real risk of causing the expansion differential in cast iron that makes it pull itself apart like what often happens when welding cast iron without preheating the whole thing to 900F and ramping it back slowly.

 

[Flad]

Lock tight has it's uses, how ever the whole thing is about nuts and bolts if they are new and up to spec the correct torque is all that's needed, mass production and lack of quality control in manufacture of fasteners along with poor engineering is why lock tight has it's uses in industry, used and stretched threads are more common reasons for using these products, most high end equipment manufacturers recommend replacing nuts,bolts and washers to avoid loosening in service, example head bolts on engines.
Another issue is if spring washers are used under nuts or bolts these things are one time only use and should be replaced, I have seen plenty of examples of a flat washer being put under a spring washer, totally defeats the purpose of a spring washer.
If you must use these products clean all threads properly and give the product time to cure.

I have never liked using these thread lockers, my theory is if it's properly engineered there is no need for any of this goop, it's best to find out why the bolt or nut comes loose and cure that problem, elongated holes or the wrong size bolt are often the cause on farm machienary.

A cheap and effective way of knowing if a nut or bolt is loosining is to get some of your wifes brightly colloured nail polish and paint it on the end sticking out of the nut or around the head of a bolt, it does two things 1 it seals the thread keeping rust out from the end, 2, if it comes loose you can see it crack, it's easy enough to remove with nail polish remover or acetone, some manufacturers use a similar product on Items they don't want you to take apart or tamper with for warranty reasons.

 

[ArlyA]

I worked for a company called Telelect* who made digger derricks, booms and over-centers for the power industry. One of the jobs my department did was install the big bearings that the whole thing rotated on which were about three feet across. These were held on by a bunch of 5/8, grade 8 bolts and the company didn't want these to come loose, so we used red loctitie on them. We torqued them down with very large torque wrenched, the largest I ever used in my life. These bearings are located just below the operators seat in this picture. *Terex today

 

[coondle]

Not directly tractor related but:
Recently I completed a 2500km (1500 mile) remote and I mean very remote trip on gravel roads and the majority on an unmade two-wheeled track (1750km) 1100miles rear crosses 5 deserts. It was the Canning Stock Route in Western Australia, often referred to as the longest bush track in the world. Google Canning Stock Route. The total distance (home to home) I travelled including a 500 mile trip to buy a set of replacement tyres was 7500 km (4660 miles)

Corrugations were huge and unrelenting for literally hundreds of miles at a stretch, the town at one end has a population of 700, at the other a town of about 3,000 with literally only 2 first nations communities of a hundred or so along the way. Twi hundred and fifty miles off to the side at one point there is a mining town of about 10,000 and 650 miles off to the other side is Alice Springs a town in central Australia. I think you get an idea of how remote the area is.

My vehicle is fitted with a winch, the bolts securing it to the vehicle either snapped (one) or rattled loose, another leaving two securing it. But when I needed iy to recover my stranded vehicle the winch was inopererable because all three struts holding the motor and gearbox together across the winch drum had vibrated loose and the winch literally fell onto 2 parts.

That folks is when I wished I had disassembled the new winch and used red loctite. The bolts all had had a retaining compound on them, some grey goop but it was not up to the pounding of the corrugations had given.

 

[Surshot]

I get red Locktite in on stuff all the time. A giant PITA. I do not use it on anything. Lock washers, lock nuts and proper torque.

 

[Raul-02]

proper torque.

What he said. Twice

 

[daryelcorran]

I find the red vs blue specs differ per brand.For some brands, red is medium and blue is the one you'll need a heat gun to unscrew afterward. For others, it's vice versa.

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[MichiganIron]

I find the red vs blue specs differ per brand.For some brands, red is medium and blue is the one you'll need a heat gun to unscrew afterward. For others, it's vice versa.

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The issue of bolt "tightness" has been debated and tested at length across several industries, with different approaches adopted depending on the application. In the Structural Steel industry, there are several specifications published by AISC to address the relationship between Torque and Tension, and the effects of fatigue on fasteners.

In the compact equipment business, the approach needs to be slightly different for a couple reasons; re-used fasteners, temperature effects of dis-similar materials, and vibration. Re-Used fasteners can lead to improper tightening based only on torque. Damaged, deformed, and corroded threads can give improper tightening based strictly on torque. Bolting into dis-similar materials is a big challenge due to the variations in thermal expansion when a piece of equipment gets to operating temperature (high strength steel bolt vs. cast iron transmission and engine block). And then of course there is vibration.

So for the application discussed here, we use recommended torque values and Loctite 246 on anything that bolts to the cast iron chassis or engine in the tractor. The high heat rating of the 246 gives us additional protection against the effects of dis-similar thermal expansion and vibration. This also allows for removal for service if required.

Just another approach that has worked well for us.

 

[SmallChange]

A cheap and effective way of knowing if a nut or bolt is loosining is to get some of your wifes brightly colloured nail polish and paint it on the end sticking out of the nut or around the head of a bolt, it does two things 1 it seals the thread keeping rust out from the end, 2, if it comes loose you can see it crack

I worked briefly for NASA in 1963 doing this for critical assemblies that went onto the tower next to the rocket to keep the tanks topped off until the moment of launch. They told me it was called "torque painting" and they used specially formulated paints that had an odd mix of many obscure ingredients, the purpose of which was to make it practically impossible to imitate the paint. This torque painting was done to make Soviet sabotage less likely and more easy to detect after the fact if it did happen. The paint was very special, yes, but it was put in ordinary nail polish bottles.
The reason I was hired to do this was that I was only 6 years old at the time, and could fit into small places. These assemblies were too big to reach into and too compact to crawl into for adults. I crawled in with a mirror and a paint bottle. Engineers outside had me position the mirror and point to fasteners as they guided me, and when I was pointing to a fastener that needed torque paint, they'd say "Yes, paint that one", and we worked our way through the whole thing. I got some kind of paper certificate from NASA (which was a pretty young agency at the time) and we kept it posted in the kitchen for years.

My contribution to the Loctite discussion: I had a hard time keeping the urethane bucket edge tight every winter. I tried fine threads on stainless nuts and bolts, which are less likely to come loose, but one of them seized during disassembly one spring and it took a lot of work with a grinder to get it disassembled. In retrospect, fine threaded stainless is particularly prone to this and was a bad idea. So I went back to coarse threads on zinc plated steel, but with purple Loctite. That worked great! Just a bit more effort to break loose, no problem. And all of them stayed put until I put the wrench to them.

 

[bigtiller]

I worked briefly for NASA in 1963 doing this for critical assemblies that went onto the tower next to the rocket to keep the tanks topped off until the moment of launch. They told me it was called "torque painting" and they used specially formulated paints that had an odd mix of many obscure ingredients, the purpose of which was to make it practically impossible to imitate the paint. This torque painting was done to make Soviet sabotage less likely and more easy to detect after the fact if it did happen. The paint was very special, yes, but it was put in ordinary nail polish bottles.
The reason I was hired to do this was that I was only 6 years old at the time, and could fit into small places. These assemblies were too big to reach into and too compact to crawl into for adults. I crawled in with a mirror and a paint bottle. Engineers outside had me position the mirror and point to fasteners as they guided me, and when I was pointing to a fastener that needed torque paint, they'd say "Yes, paint that one", and we worked our way through the whole thing. I got some kind of paper certificate from NASA (which was a pretty young agency at the time) and we kept it posted in the kitchen for years.

Very interesting story. Did you keep the certificate?