During my recent front suspension rebuild, I was wondering what the ' blue ' compound was on the new bolts supplied with the struts.

Looked up Loctite for info and found a few things I hadn't come across before.

Most loctite liquids only work with certain metals. Needs an ' active ' metal to set up.

Sets up due to oxygen free environment inside the thread area. Stay liquid out of that area. Bottles pass through oxygen to keep it liquid.

Some need a primer.

Green loctite can be applied after assembling and/or torquing. Possibly also one of the blue ones.

Red is pretty much intended only for permanent fittings, can require high heat to remove.

Comes in tape and paste form.

Has one for plastic tighteners.

What I couldn't find, even after contacting Loctite corp via email was:

How much to adjust torque setting due to lubricant quality of liquid Loctite.

How long after assembly can the final proper torque be set.

Does retorquing for quality control impact loctite holding power.

If retorquing impacts holding power, can green Loctite be applied to hold that joint.

Found that the split lock washers are not very trustworthy for metal surfaces.

Found there is a lot of controversy on how ' jam nuts ' impact a torqued connection. Some say, put the smaller nut on the bottom. Others say put it on top. Lots of arguments, just like asking which brand oil to use.

Smaller than what? On the top or bottom of what?

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My error, meant to say jam nut. Corrected it in post.

Lots of confusion on how they are used and how they impact the intended clamping force.

After lots of reading different opinions I don't know which to believe. I know they 'lock together' so they are each more difficult to turn, but I don't know how their use impacts setting a proper torque for the clamped pieces.

This seems convincing until other opinions are read:

https://www.bluetoad.com/publication/?i=228390&article_id=1832307&view=articleBrowser&ver=html5

Also read that nuts are usually made from a softer material so the threads can deform easier to spread the load on more threads of the bolt. A hardened nut will have most of the load on the threads closest to the clamped piece and very little load on the remaining threads. Apparently this 'deforming' of the threads and stretching of the bolts is probably the reason to use new nuts and bolts if possible to reduce failure plus allow proper torque setting for clamping.

A jam nut acts as a locking brace against the torquing nut, it should not apply any additional torque to the assembly. Meaning, once your torque has been set by your main nut, a wrench is applied to that nut to hold it in place while a jam nut is tightened onto it. The flats of the two nuts should be nearly aligned with a slight degree of advance on the jam nut indicating it has taken up any slack in the threads against the torque nut but without turning the torque nut from its torqued original position. This locks the two together making it very difficult for them to back out. On the otherhand, if you tighten the lock nut and dont fix/hold the torque nut and they both turn, then yes, you are affecting the torque setting altogether.

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Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)

I always use red. I don't put on more than a drop or two. They'll come off if used in this manner.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

One Loctite oddity that never made sense was their packaging and product color mismatch that changes depending on package type. Some loctite Red products come in Blue packages, where as some loctite Blue comes in a red bottle. The small toothpaste tube varieties are often matched, Red to red, Blue to blue, but the slightly larger bottles seems to go opposite. Read the label to make sure. Otherwise great product.

__________________
Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)

What I couldn't find, even after contacting Loctite corp via email was:

How much to adjust torque setting due to lubricant quality of liquid Loctite.

It is supposed to be a 15% reduction in torque vs dry assembly per standard aircraft procedure

How long after assembly can the final proper torque be set.

Depends on how active the metal and finishes are. Can be a minute or two for an old steel bolt into a cast iron hole, to several hours for some stainless steels. Temperature also makes a difference.

Does retorquing for quality control impact loctite holding power.

No, applying a torque equal to the installation torque is an accepted practice.

If retorquing impacts holding power, can green Loctite be applied to hold that joint.

The older loctite will prevent the green loctite from wicking into the thread area.

Found that the split lock washers are not very trustworthy for metal surfaces.


Try using Nord-lock washers. The most secure lock washer on the market. Available from Amazon.

Found there is a lot of controversy on how ' jam nuts ' impact a torqued connection. Some say, put the smaller nut on the bottom. Others say put it on top. Lots of arguments, just like asking which brand oil to use.[/QUOTE]


You put the jam nut on the top per standard aircraft procedure.

Other official aircraft tips;

Loctite has a one year shelf life for new aircraft assembly. The Loctite bottles are actually porous and allow oxygen into the tube to prevent the Loctite from anaerobic hardening. After a length of time in the tube the strength of the Loctite bond degrades. In practice, two to three years is about as long as Loctite lasts, then you need a fresh supply.

Loctite is meant to have iron based ions to activate it. Heavy cadmium plating and stainless or aluminum components will prevent the Loctite from bonding/hardening. This is why Loctite sells a liquid primer (Loctite 7649 available on Amazon) with ions in it to be applied to aluminum and stainless installations.

Whether the jam nut goes on the top or the bottom depends entirely on the orientation of the bolt. If the head of the bolt is on top, the jam nut goes on the bottom. (Generally speaking, aircraft standards place the head of vertical bolts on top, so that the bolt doesn't fall out in the unlikely event the nut does come off.)

Maybe it would be better to say that the jam nut always goes on last.

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carock

Great informative comments, thank you much.

Have always enjoyed learning from people that know more than me. You should be a consultant to Loctite and help answer peoples questions. Most likely though, they don't want to be sued based on being too specific and having something happen.