Anti-seize and over torquing bolts (1 Viewer)

[alex4640]

Full disclosure before I begin. . . I work for Loctite.

There are two main points in this thread. Regarding the original point of removability, there is only one reason bolts that are properly installed become difficult to remove later on and that is rust. I know it's hard for most people to believe, but in a typical threaded assembly, there is only about 15% metal to metal contact. (flights of the male thread touching flights of the female thread) The other 85% is air. Air which contains water and different amounts of salt depending on where you live. This is why we get bolts that are rusted shut.

Anti seize is primarily intended to prevent galling the threads as you install the fastener, especially with stainless steel parts. It is, as stated several places above, a lubricant. This keeps the male and female threads from welding themselves together (seizing) as you install. Secondarily, it remains in the threads thus preventing water from entering the threads, thus preventing rusting the threads together later on. The problem with anti seize is, that it always stays a lubricant. A lubricated bolt can more easily loosen both when you want it too and when you don't. The whole point of a torque specification is to apply a certain clamp load. You want that clamp load to stay constant until you're ready to disassemble the part.

There is a way to prevent water from entering the threads without leaving a lubricant behind. Using a medium strength threadlocker does lubricate the assembly process but it chemically changes into a hard plastic when it cures. Now you have a hard plastic filling up that 85% space. This does two things for you. It prevents unwanted loosening and also prevents rusting. So a thread locker is also an anti seize in the sense that it will take the same amount of torque to remove that fastener tomorrow as it will 10 years from now. Remember that the medium strength (blue) Loctite is removable with the same hand tools you installed with. However, if you're concerned about rounding over the heads of smaller bolts and screws, you can use the low strength (purple) Loctite. Same rust preventing benefits with lower removal torque needed.

Now, about the second topic. Torque vs clamp load for lubricated vs dry fasteners. FJ4068 is absolutely correct. It's too complicated to explain so I'll sum it up.

Torque is related to clamp load via a factor called "K"
The impossible part is that the "K" factor for any threaded assembly depends on the following:
1. diameter of the bolt
2. pitch of the flights
3. engagement of the flights
4. metallurgy of the male threads
5. metallurgy of the female threads
6. friction coefficient of the two metals describe above working against each other
7. quality of the fastener (i.e. how consistent are all the above from one end of the fastener to the other)
8. which particular lubricant? (by name and number)

So there's no way to tell you how much you should reduce A torque on A bolt. Believe me, engineers ask me that all the time.
However, if you're planning to put 30 or 40 thousand of the same nuts and bolts together and you can send me a couple hundred for testing, that's another story. That's how Toyota, and everybody else, comes up with the torque specs in the FSM.

So if I'm such an expert. . . how much do I reduce the FSM spec torque? "just a bit"

 

[western flyer]

Thanks Alex4640. I learned something here.

I was a pro bicycle mechanic in a previous life and standard practice was (and is) for most metal to metal parts get coated in grease upon assembly. The was/is to prevent galvanic corrosion and provide thread lubrication. Lots of different metals are used on high end bikes, and most of these parts are designed to be taken apart and put back together dozens of times. We also used an anti-galling agent like anti-seize for stainless parts (e.g., spoke threads). I was taught back then (1980's) by all the old-timers that Loctite threadlocker use on high end bicycle parts was relatively rare and mostly for situations where the engineers did not or could not engineer fasteners to maintain proper clamp load "normally." IOW, Loctite threadlocker was then considered a bit of a design crutch for threaded parts. A few specific bike parts normally came from the factory with threads pre-coated in med. threadlocker or similar, but its use was quite uncommon.

Later I learned about anti-seize when a LC mechanic gave me some right after I bought my first cruiser. Afterwards I over-used the anti-seize, and and then a couple years after that learned about its effects on fastener torque values and friction. Since then I have been more conservative in my use of anti-seize, and have been trying to compromise between corrosion prevention, maintaining clamp loads, and proper fastener torque values.

What you have provided above is useful for considering a med. threadlocker as an alternative to anti-seize or light oil in some situations. I was not considering threadlocker for its sealing and anti-corrosion properties. Thanks.

 

[PabloCruise]

Really enjoying this thread.

I did not know about the purple loctite.
How will it hold up to heat? The topic came up when we were talking about the intake/exhaust manifold sandwich on our counter-flow 1 & 2 F heads in the 40/55 section.

Will the heat of an exhaust manifold cook the loctite into a substrate that will make removal difficult?

 

[Timpanogos Slim]

Really enjoying this thread.

I did not know about the purple loctite.
How will it hold up to heat? The topic came up when we were talking about the intake/exhaust manifold sandwich on our counter-flow 1 & 2 F heads in the 40/55 section.

Will the heat of an exhaust manifold cook the loctite into a substrate that will make removal difficult?

In an earlier thread, someone made the argument that anti-seize should not be used on spark plug threads because the heat of the engine would cook out the lubricant and leave behind merely a thick paste of metallic dust that actually makes it harder to remove the plugs.

I would think that exhaust manifold heat would eventually reduce any color locktite to it's barest elements. I can tell you that all that remains of the anti-seize compound that got accidentally smeared on one of my heat shields is a thin coating of metallic powder.

 

[ttubb]

In an earlier thread, someone made the argument that anti-seize should not be used on spark plug threads because the heat of the engine would cook out the lubricant and leave behind merely a thick paste of metallic dust that actually makes it harder to remove the plugs.

.

Champion makes an anti-seize specifically for spark plugs. We use it in aircraft engines. T

 

[mattafact]

If I put anything on flywheel bolts, it's red loctite 262, just like you'd see on many factory fasteners used for flywheels.

If I were you, I'd carefully clean off all the anti-seize compound with some brake cleaner and compressed air, or a whole lot of paper towels and brake cleaner.

Loctite is your friend for bolts that you do NOT want to come out. Flywheel bolts would be at the top of my list for bolts that I don't want coming out.

Think of how close to your ankles the flywheel is, spinning at 5000 rpms and then letting go.... 25 lbs of mass, with gear teeth on the outside.

There's a reason that SFI specifies reinforced bellhousings on drag race cars!

Nevermind the bus load of nuns. Think of how hard it would be to walk if you're missing part of your feet. Or push on the gas pedal

Those are good points. I had a feeling I needed to redo it but it's good to have confirmation.

 

[alex4640]

I'll try to answer the two new questions without getting too commercial.

Anti seize on sparkplugs should be fine. The grease does in fact cook out for the most part. However, the left over "metal powder" still works as a lubricant to help you remove the plugs. Think of it like a "dry molly" lube or the graphite powder you used to drown your Pine Car Derby wheels with.

As far as using thread locker on your exhaust manifold, you just have to use the correct product. Unfortunately, you will not find the correct Loctite product at your local auto parts store since it’s not a consumer product. Loctite 2422 can withstand sustained temperatures up to 650°F but it’s an industrial product. You may find it on McMaster Carr or at a local Fastenal industrial supply house. Same thing goes for the purple Loctite 222.

 

[livinoffroad]

Great discussion. I always learn from "mud".

My experience with anti-seize comes from the pleistocene period, back when I repaired Caterpillars for a living.

These ferocious creatures constantly wallowed in mud, salt, and created enormous heat.

Heat soak was a common phenomenon, where after a long day of working hard in the California heat, the exhaust manifold would glow a dull red in the twilight.

By the time I was leaving the trade, (1980's) Caterpillar was phasing out the grade 8 "deep head" bolts, used throughout the machine, which were really nice to have. You could get a really good grip on them, to break them loose, after some other ham-handed mechanic (99% of them) had over tightened them.

(These bolts were great, because, even if the head was half worn away by abrasion against the dirt, you still had plenty of meat left on it, to get a good grip.)

This is where anti-seize comes in handy. As discussed, it prevents galling (welding), and fills in the "interstitial" spaces between the threads where mud, salt, carbon, water, and other oxidizing elements effects are magnified by heat.

Very corrosive environment. This is the appropriate application for anti-seize. If you don't have a thread chaser to clean the dirt out of the threads, mix a little "Never-Seez" with it!

Conversely, anti-seize is not appropriate for engine internals. Torque specs for internals are usually meant to be used with a light coating of thin motor oil.

I have learned over the years to use a light touch, especially with long handled wrenches, or with low vibration applications. You'd be surprised how much clamping pressure a bolt can apply, and stay tight, even without lock washers, or flat washers.

Very enjoyable, the next time you have to disassemble.

 

[Timpanogos Slim]

I recently assembled a harbor freight trailer. Did i use anti-seize? On every last freaking bolt i did.

No torque specs, nylon insert lock nuts on almost every bolt. And if i ever have to take it apart, I want it to come apart.

I used it on my recent spark plug replacement and i may or may not do that again in the future.

I dunno whether I'll put it on lug nuts in the future. Maybe a little. and carefully.

I'm convinced that i shouldn't use it on the engine itself, like when i do the valve cover in the spring.

 

[hrt4me]

good to know, thanks!

 

[OverLand Cruisers]

Good stuff!!!

 

[OLDSRIP]

Excellent reading, thanks guys

That 85% air space is amazing. No wonder things rust together so bad.

Looks like I will substitute thread locker in some cases. I didn't realize it was a lubricant at first.

I live in the rust belt and use never seize often on most things that get taken apart.
I have only had 1 problem that I remember. That being a caliper bolt on my 80.
Lock tight from now on.

Joe W.
94 80 series




Joe W

 

[SM Racing]

For the record, I love antiseize. However Porsche doesn't recommend antiseize on spark plugs. They claim it actually insulates the plug slightly thus changing the heat range. For most applications that may not be such a big deal, but in other applications it can be critical. Something to keep in mind.

 

[musthave]

Wow, thanks for the excellent information. I've never seen the purple version, will have to look for that now.

 

[86tuning]

My experience with anti-seize comes from the pleistocene period, back when I repaired Caterpillars for a living.

These ferocious creatures constantly wallowed in mud, salt, and created enormous heat.

Awesome. Just awesome.

 

[MrMoMo]

Alot of my stuff I follow the FSM and use a little more torque when I use anti seize.

Uh, dude.... Hate to say it, but that's backwards. The anti-seize reduces the friction, which means that you reduce the torque value with anti-seize, otherwise you risk over torquing the bolt (because it turns easier). If you tighten it more, you are even more likely to over torque the bolt to it's yield...

 

[CruiseOrlando]

Uh, dude.... Hate to say it, but that's backwards. The anti-seize reduces the friction, which means that you reduce the torque value with anti-seize, otherwise you risk over torquing the bolt (because it turns easier). If you tighten it more, you are even more likely to over torque the bolt to it's yield...

No no no... he's just starting phase-1 of Landtank's method...

I always fall back on the tried and true procedure of torque to snap. You basically tighten the bolt until it snaps and then back it off a 1/4 of a turn.

 

[NLXTACY]

Can't forget about torque-to-snap

 

[MDarius]

I was pondering Anti-seize last night as I drifted off to sleep, wondering how a bolt is supposed to stay in place when it's covered in something that reduces it's friction. Today I found this and thought it was so great it deserves revival, if not an entry into FAQ. The discussion about the benefits of Loctite and Anti-seize should be common knowledge for any shadetree mechanic, but I didn't get it. Thanks to the Mud-fathers who explored this in days past!

 

[zhloea]

I hate that I saw this post so late, I currently work on a car, its trans mount bracket to the trans block bolts require 51 flb torque, the bolts have some kind of rust issue, so I used the rust evop to remove the rust then coat it with anti-seize then I installed it without reducing torque, of course, I did not see it strip the block tread at that time....but I am wondering that:

Should I back to loosen them and re-torque them again with a reduced torque value?
If I just leave it along will these kind of over-torqued bolts damage the trans block thread in the future?