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Discussion Starter #1
General question: Should threads be lubed on a bolt or nut prior to torquing it down to spec? Or leave it dry?
 

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Invader's response/article was regarding spark plugs that are inserted in aluminum head. In that application, NGK recommended special plated metal threads, without anti seize.

Were you referring to bolts in general?

It depends on the application. When doing internal engine component torque (i.e.- connecting rod bolts), it's common/advised to use an oil to lube threads.

General question: Should threads be lubed on a bolt or nut prior to torquing it down to spec? Or leave it dry?
 

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"Most times, the specified torque value assumes clean and dry parts. Clean means no dirt, rust, dried-up gasket sealer or anything except shiny metal. Wire-brushing the threads will help remove rust or sealant. Engine fasteners, like head bolts or main cap bolts, are often specified to be torqued with 30-weight engine oil wetting the threads and washer. If you're installing a fastener that has a dry torque spec, and the threads and bolt face are oiled, you'll need to reduce the torque by 15 to 25 percent, because the slipperier surfaces will decrease friction. Teflon-bearing lubes or moly-sulfide engine assembly lubes can reduce friction enough to require a 50 percent reduction in tightening torque. Even casually substituting a zinc- or cad-plated bolt or washer for an unplated one calls for, respectively, a 15 or 25 percent reduction in applied torque, because the plating acts as a lubricant. Fail to heed this advice and the fastener will be seriously overtightened. You'll either snap it or crush a gasket to the point where it leaks.

On the other hand, rust or burrs on the threads can increase friction enough that a fastener tightened to the specified value won't provide sufficient clamping force. The shop manual will specify whether the fastener is supposed to be dry or lubed. In either case, prep your bolts. Don't forget that residue from the parts washer or that pie tin full of kerosene you're using to clean parts has oil in it. Even a quick blast of compressed air to dry off a fastener will leave an oily film behind, affecting ultimate torque. If you're really fastidious, clean up with some aerosol carb or brake cleaner, followed by more air. If you've used grease or anti-seize compound to keep the brake discs from seizing to the hubs, take care not to contaminate the studs or lug nuts."

How to Use a Torque Wrench
 

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Also note that using a thread lock acts like a lubricant - so beware if bolt is normally torqued dry.

Generally if you are told to torque a bolt you follow the instruction. If it tells you to use lube you use lube etc, if not it is dry.

Service manuals will always tell which bolts need lube when torquing bolts... even the Versys Manual.
 

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Also note that using a thread lock acts like a lubricant - so beware if bolt is normally torqued dry.

Generally if you are told to torque a bolt you follow the instruction. If it tells you to use lube you use lube etc, if not it is dry.

Service manuals will always tell which bolts need lube when torquing bolts... even the Versys Manual.
+1 Follow the manual, if you don't clean, lube or add anti seize / thread lock, you risk overworking said bolt.
 

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For lighter torqued bolts, the oil with vibration could prematurely loosen the bolts too. Eventually, they all will loosen with steady use. Torquing in manufacturing is a big money maker because it takes a lot of money to make sure you have the best torque assuming a lot of sequential dynamic operations with 'any' (dumb low-wage) operator.

If you were to emulate the torque wrench in your wrist, it would be inordinately expensive, as long as your timing and sequencing is correct. And personally, I'd go with that over blind torque wrenches without knowing the proper sequencing, cleaning, and inertia effects which is beyond the scope of this thread or wiki. ymmv. There is always a chance of screwing up depending on a lot of things beyond your control (i.e. - Chinese part batches mixed in production.)
;-)
 

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Discussion Starter #8 (Edited)
Great info. Thanks all!

The question came up for me due to torquing the rear axle bolts after adjusting the chain. The nut binds a bit at about 50 or 60 ftlbs, then breaks free and easily rotates a little bit, then binds again with it taking maybe 80 ftlbs to move it again. These are small 1/10th of a turn or less movements. It doesn't rotate smoothly with a gradually increasing amount of torque required. As if it needs a bit of oil to get it to tighten smoothly.

Since I've never seen any mention of lubing the threads on the axle, I'll just keep it dry. Next time I have it off (tire change in the near future), I'll clean the threads and the mating surfaces.

But all of that led to the general question because all the bolts have a torque spec in the manual and I've never seen specific guidance on prepping bolts or nuts before tightening.
 

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...But all of that led to the general question because all the bolts have a torque spec in the manual and I've never seen specific guidance on prepping bolts or nuts before tightening.
IF I used Loctite on a bolt, I "chase" the threads to clean them before I re-install them.
 

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What has not been mentioned in this discussion is wrench calibration. Honestly how often do we bring our torque wrench in to an established weights and measurement agency and have it calibrated? I venture to say, never. So the argument is not only whether or not torque to spec, clean, dry, lubed or dirty, but also adding in whether the tool you are using is accurate.

So it you need 120 ftlbs are you really getting it? or are you getting 126 or 114? (+/- 5%) ?
 

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I costs way more to have a wrench calibrated than you paid for the wrench.

I back off about 10% when using Loctite. I back off about 25% when using anti-seize.
 

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I costs way more to have a wrench calibrated than you paid for the wrench....
UNLESS you have a Snap-On (I have two - a 1/2" 'clicker' and a 3/8" 'dial').

They are the ONLY company I know of that will calibrate your torque-wrench 'forever'....

After use, you should ALWAYS set it back to the MINIMUM setting.

:thumb: - :thumb:
 
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