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A question for the engineering types out there.
I know that when using lube/sealant/anti-sieze/etc on fasteners that may not normally have it you should reduce the amount of torque applied to the fasteners, but by how much??
Is there a general rule-of-thumb like 'reduce torque values by x%' where x = 2 or 5 or 10 or other??

I've always had a bad habit of over tightening fasteners, sometimes resulting in breakages (fortunately never on the bird) so I'm always careful to use my torque wrenches whenever possible when working on the bike. Despite this I still think there are some bolts I've over tightened as a result of using some compound on the threads.
I'd like to know what other people do just so I can reduce the likelihood of damaging anything in the future.


This question might be more suited to the General Motorcycle Discussion forum, if so Mods feel free to move it.
 

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Good Question, I'm interested in the replies from those in the know, I often use a little grease to lube the threads but, tend not to torque the smaller fasteners in case the lube has affected the reading and end up guesstimating when they're tight enough.....................
 

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As a really blunt statement (and ignoring 101 caveats) 10%.

To do the job properly you need to specify which lubricating oil you are using, how the thread was formed, the bolt strength, if the bolt is new ...............etc etc

For example use graphite on a 12mm thread and there will be ~50% difference in the force to torque compared to dry even when a torque well below bolt yield is specified ...... which is probably why people encounter broken/stretched bolts. 'Luckily' the specified torques in the W/S manual are low (compared to yield) so apart from M6 bolts you are never likely to break a bolt .......
 

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Come on, bolting calcs are exciting stuff, nearly up with weld fatigue in my bed time reading.
I bet you're a hoot at campfire gatherings. :poke:

In all seriousness though, good info above. So you would say that, as far as XX fasteners go, a 10% reduction in torque is a good rule of thumb when thread locker is applied?
 

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Shewie said:
10% reduction in torque is a good rule of thumb when thread locker is applied?
ummmm if you are lubricating a thread you wouldn't be applying thread locker as well since you would be trying to 'stick' something that you had deliberately made slippery! (just stating the bl..ding obvious since this thread is about lubricating threads)

If re-using a bolt (dry) and applying thread locker I would drop the torque by up to 10% on something like an M10 with a cut thread (less for smaller dia bolts since the intial wear will be less).
With a rolled thread I wouldn't drop the torque when re-using.

If you lubricate the bolts they will feed through the female thread much more easily and it is then that overstressing can occur since you will keep winding until the torque wrench says you have got to the correct torque ............. but in achieving that torque you will have exceeded the preload that was intended for that joint.
Sometimes you just have to lubricate threads (stainless and titanium especially due to their habit of galling) but generally dry is best.
That said when re-using a bolt it is never clean so any corrosion will tend to increase the force needed to turn it and on the other side even natural oil on everybody's skin has lowering effect.

The thing to remember is that the torque applied is simply a method of achieving a preload on a joint so unless the designer was a) totally clueless b)restricted on space the bolt should always be able to take a level of abuse.
 

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Made this thread sticky.

Pun intended! :D

Moved to Resource Center too. First class technical information.
 

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ummmm if you are lubricating a thread you wouldn't be applying thread locker as well since you would be trying to 'stick' something that you had deliberately made slippery! (just stating the bl..ding obvious since this thread is about lubricating threads)
Thread locker (at least Locktite in liquid form) does act as a lubricant until it sets, Mr. Smartypants.
 

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Preload is a function of torque appliad, bolt diameter D and nut factor K in its simplest form.

Fp=Torque/(KxD)

Unfortunately nut factors, K has a wide variation using the same fastener, then there is a wide variation dependant on:

Base material, grade, plating, oil, rust, lube, loctite, antiseize etc

generally K is determined experimentally. A rough example of mean (average nut factor is)
Moly Paste, K =0.13
Copper Antisieze, K =0.132
Alloy Steel, K =0.2
Dry Cad Plate, K =0.2
Dry Zinc Plate, K =0.29
Very Rusty, K =0.39

Loctite will not tell you thier effect on K, in my experience loctite is a mild lubricant somewhere between dry and anti-sieze.
This is simplified as there are other factors.
K
 

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Thread locker (at least Locktite in liquid form) does act as a lubricant until it sets, Mr. Smartypants.
Oh I accept that (and karlxx's later comment), what I was trying to get over (and obviously failed to do) was that if you have a base layer of oil on a thread and then add the thread locker you are trying to get the thread locker to 'go off' on a surface that you have made deliberately 'slippery'. Since the purpose of the thread locker is minimise the effect of vibration on the fixing*, by lubricating it in the first place you are making the fixing more likely to be vibrated loose ......hence you are taking two actions that fight against each other. (obviously assuming they are chemically compatible)

karlxx has made a good point (I spot another engineer!) that has made me think of another 'interesting' point directly connected to the subject of lubrication of bolts, namely the form of the 'head' (bolt of bolt and nut).

Whilst lubricating the thread will make it easier to spin the bolt in this has little effect on the strength of the joint since nothing is being clamped up at that point.
When the bolt head/nut comes into contact with the part that is being clamped the largest friction generated is between the bolt head/nut and the part .....and that also has a large effect on the torque being applied ..... so put a blob of grease under a bolt head/nut and you could again over torque a bolt.
Our bikes are mainly held together with hex head and cap head bolts/screws so if considering swapping from one to another it is worth bearing in mind the different head areas before winding the 'set' torque on.

But that is where washers come in and they change everything .....


* Thread locker is also used where there is a tendency for the clamped parts to rotate and where creep induced relaxation could be a factor (not relevant on our motorcycles but something I've had to deal with in the past where 150 year lifespans are 'normal')
 

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Oh I accept that (and karlxx's later comment), what I was trying to get over (and obviously failed to do) was that if you have a base layer of oil on a thread and then add the thread locker you are trying to get the thread locker to 'go off' on a surface that you have made deliberately 'slippery'. Since the purpose of the thread locker is minimise the effect of vibration on the fixing*, by lubricating it in the first place you are making the fixing more likely to be vibrated loose ......hence you are taking two actions that fight against each other. (obviously assuming they are chemically compatible)

karlxx has made a good point (I spot another engineer!) that has made me think of another 'interesting' point directly connected to the subject of lubrication of bolts, namely the form of the 'head' (bolt of bolt and nut).

Whilst lubricating the thread will make it easier to spin the bolt in this has little effect on the strength of the joint since nothing is being clamped up at that point.
When the bolt head/nut comes into contact with the part that is being clamped the largest friction generated is between the bolt head/nut and the part .....and that also has a large effect on the torque being applied ..... so put a blob of grease under a bolt head/nut and you could again over torque a bolt.
Our bikes are mainly held together with hex head and cap head bolts/screws so if considering swapping from one to another it is worth bearing in mind the different head areas before winding the 'set' torque on.

But that is where washers come in and they change everything .....


* Thread locker is also used where there is a tendency for the clamped parts to rotate and where creep induced relaxation could be a factor (not relevant on our motorcycles but something I've had to deal with in the past where 150 year lifespans are 'normal')
Why would I oil the threads if I was planning to apply Lockti...Good grief. Never mind, I'll just go back to the old fashioned method of "tighten until it strips then back it out 1/2 a turn".
 

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Why would I oil the threads if I was planning to apply Lockti...Good grief. Never mind, I'll just go back to the old fashioned method of "tighten until it strips then back it out 1/2 a turn".
HA HA HA , you bloody engineers, Come to oz and make my workshop parts for me i could do with a bit of direction,HA HA HA, Don't want to seem rude but i'm a bit old school engineering wise but i can make a strawberry out of shit,Was on the CNC last week and hit the comp to see my working logs and have made 42 different bits in the last 18 mths ,What is locktite :smilebig:
 

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Good info this. I made the mistake of thread locking the brake calipers. The nut side came free without issue, but the Allen key side...... Freakin absolute hell to get 1 of them off. Had to tack weld a nut on it to get it off. My mate who helped me is a 70yo ex speedway racer who is a guru at building bikes, told me to literally throw the Loctite in the bin :lol:
 

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Sounds like you used a lot of loctite. You only need enough to cover a couple of threads around for most smaller bolts and about 4-5 threads on larger. Also it depends on the grade of loctite being used. Blue=removable, red=Don't want to remove but can, green=you'll never get it off.

I've been finding on my bike the PO went nuts with loctite and some other stuff which reminds me of hardened plumbers putty. Thank's for the info Duck about how much less torque needed even with loctite being used and the big percentage with graphite. I don't use graphite and wouldn't know when to except for locks. I do use Never=Seize and still use same torque. Wrong? I did know about lubed and non-lubed. A lot of specs will specify.

The other factor I see is the torque wrench being used. Bar or clicker? How well calibrated? Then there is the torque to yield bolts, don't really know how well they work all the time. Good topic.
 

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Then there is the torque to yield bolts
another world all together!
Off the top of my head I think they were originated to speed assembly in the automotive world (head bolts?) when using not 100% accurate air tools. That way any excessive torque would be negated by the stretching of the bolts and they have the advantage that you don't have to re-torque the bolts after a couple of hundred miles.
This type of bolt is strictly one use only and then bin ..... which takes me back to the Bird. If you read the Honda W/S manual it says to replace the bolts when you have pulled the callipers. When I first got my Bird and started spannering it I looked at these bolts to see if Honda had used stretch (one use) bolts ..... No they didn't (and dealers don't replace the bolts either) so why the instruction? I can only assume it is because new bolts have a band of red thread locker on them and Honda have naturally taken the safety first approach (or if I was less forgiving they can make money selling spares).
 

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Discussion Starter #20
Wow, some pretty full on information there. Thanks to The Duck and karlxx for some excellent info! :clap:
I knew it was a bit of a tricky question with lots of variables but I think this gives a pretty good idea.

The main bolts/fasteners I'm thinking of in relation to the bird are:
1) brake caliper bolts - loctite
2) cam cover bolts (the cam covers that holds the cams in, not the valve head cover) - moly-b oil (50/50 mix moly b grease and engine oil)
3) header nuts - anti-seize

I know my right side XX brake caliper bolts stretched after a number of uses. Will try to get a pic. A few times I re-used them before the F4i mod and you could actually feel something not quite right when torquing up. Almost like it was just about there but then it would still go another quarter turn or more. Always gave me a bad feeling in the gut.

I used some moly-b oil on the cam cover bolts as I didn't have anti-sieze. The first time I pulled these bolts it almost felt like they were going to snap just by trying to slacken them off. So I put some moly-b oil on them as an interim 'anti-sieze', but recently on one or two I got the same feeling as the brake caliper bolts. I really don't want to be snapping one of these off in the head, or worse, stripping the thread. They seem the same type of bolt as the brake caliper bolt only thinner (6mm?) so I'm guessing it was the bolt stretching. All has held ok for a while but I'm seriously considering replacing them all as a precaution next time I'm in there.

And I've read a number of threads on the header nuts about not torquing them up, just pinch them up and check for exhaust leaks then adjust from there. I've got my headers off at the moment for ceramic coating, when I come to putting them back on I'll be going this route to be safe (with a bit of proper anti-sieze).
 
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