Anti Sieze on Cylinder Studs?

[KDXSean]

I put anti sieze on lots of stuff, but is there any reason you shouldn't put it on cylinder and head studs too?

Had one nut stick on a base stud. The stud backed out of the case, so I was lucky it didn't break off.

All opinions appreciated.

Sean

[bradf]

There is no reason to say absolutely "no" to your question. However, putting anti-sieze on a steel nut that is on a steel bolt/stud is not necessary. It will aid in lubricating for proper torque but so will light oil. Anytime steel goes onto aluminum it is highly advisable.

[IdahoCharley]

Anti-sieze or oil on threads will change (reduce) the torque value that should be use to tighten the fastener. But if you allow for this: then anti-sieze or oil could be used.

[bradf]

IC, I disagree with your statement. The thing that reduces applied torque or impedes torque giving false readings is the dry friction between the fasteners such as a bolt and nut. Adding any lube, whether it be light oil or moly, will only help achieve a more accurate torque by overcoming the friction. Every engine builder applies a lube to all critical torqued bolts (head, crank, rod, etc). At least every smart engine builder does it.

[RBD]

I have to agree with "bradf"....., when you torque fasteners you want to eliminate any un necessary friction and galling.

Ron

[Ryan]

i third that

[IdahoCharley]

I agree with the statement that you ...want to eliminate any 'unneccessary friction and/or galling'. For the subject matter in this thread however, that is limited to clean, dry and ungalled threads on the fasteners and related fittings. e.g. nuts, stud hole threading, threads on the bolts, studs, etc.

The dry interface friction of the threads is already compensated for (in the assigned torque value). Fasteners like studs and bolts used in mounting heads and cylinders are selected for a certain clamping force that will remain relatively constant over a specific temperature range. They need to grow and contract (relative to temperature and pressure) similar to the material they are clamping. To perform this function the fasteners should remain in the yield range for their base material.

If lubication of the threads takes place and a higher torque is used for fastening the fastener - you are taking the chance of going beyond the yield strength of the material and thus losing the ability of the fastener to perform it job.

1. Possible tensile strength failure evidenced in the side pulling or shearing of the threads i.e. "pulled threads" or "strip out threads"

2. Possibility that bolt or stud is rendered essentially unsuitable for the application because it will not grow and contract as originally intended. (structual material properties changed - went beyond yield strength of base material). You may not know this right away unless you have tensile failure in the material. (Bolt/fastener snaps off while your tightening it)

The point of applying torque which is beyond the yield strength for the material but below the tensile strenght can lead to failure down the road/trail. Due to the over-stressed fastener allowing the clamped parts to loosen, because the fastener can no longer maintain a constant clamping force at different temperatures and pressures.

Typically fasteners for dirt bike application will be specified for a dry torque value: The engineer assumption is that threaded fasteners and connecting hardware are of a specific grade meeting specific ANSI specs and tested to ASTM specs or their equivalent European/Asian testing specs.

If you want to assemble your bike's motor to the correct torque values -then ensure the threads are clean and dry. And the underside area of the bolt head (or nut) which contacts the adjacent clamping surface is not galled or scared. And replace the interface copper washers if they are specified in the design.

If you must lubicate something to feel good - then lubicate the contact surface on the bolt head where it contacts the washer or bike head: don't lubicate the threads UNLESS you reduce your torque values appropriately for the lubicate being used.

FWIW There are many tables of torque values verses lubicates verse yield values available. http://www.aztecbolting.com/downloads/torque_values.pdf
http://www.vfbolts.com/torque_value.htm
http://www.zerofast.com/torque.htm

P.S. Concerning car engines - its been awhile since I've built any, but we used to measure the growth of the rod bolts in lieu of using a torque value to be more accurate. (Actually in an attempt to ensure our engines would last)

Question - Once you degrease and engine and have all the machine work done prior to reassembly what is usually the next step? Answer - Chase all the primary threads in the block (main bearing and head stays) followed by blowing out every tapped hole on the block and head(s). This was normally done prior to trial assembly or fitting up of any parts.

The high performance GM and Ford manuals did provide torque readings for the main caps, oil pump and head bolts with lightly oiled threads. I seem to recall they specified 10 weight motor oil: But I could be wrong here.

[bradf]

IC, that was some more fun and interesting reading. Can't argue with those authors and articles. Learned something new again. Now I wonder about using loctite where the oem had none. I wonder how much of a change there is using blue or red as I do on bolts like the rotors or fasteners that I just don't want to come loose. I guess we must assume that the engineers expect it to be used on rotors as it came that way from the factory. On car engines I know that virtually every manual called for oiling the critical bolts so that must have been considered back then. Back in the early to mid 90's there appeared bolts used on aluminum heads that were not torqued. They were turned x amount (measured in degrees) past the point where they made contact. The bolts were "stretched", used once, then thrown away if removed. So back to this discussion. From now on I do it dry unless instructed otherwise.

[IdahoCharley]

Bradf - you must be one sick man if the above reading was fun or interesting

However for your reading enjoyment - concerning loctite applications - rest assured that loctites formulations were done with compounds that would not drastically alter assembly torque values (in most cases) because after all, loctite wanted us to buy and us it. (profit incentives)

http://loctite.fast.de/wwdh/us/i054ch03.htm

[bradf]

Years ago I talked to the ARP rep (htey were a sponser) that told us that their torque values were directly related to bolt stretch. ARP had the engine builder do a few tightenings and loosenings before the final assembly of the crank/rods to "smooth the threads out". They always used motor oil as a lube. I am figgering that ARP had the motor oil factored in as well as the smoothing issue. That would also explain why the newer fasteners are not torqued but stretched a certain amount to obtain the desired clamping value.

[IdahoCharley]

For the really really bored person only!!

FWIW - Torque values for critical fasteners are always based upon a percentage of the yield strength. Typically it seems like fasteners are spec'd for somewhere between 50 to 80% of their yield. But the adjoining material properties also play a important role.

Minimium thread depth engagement of a fastener (like a bolt or stud) will change based upon the material the fastener is made from and from the base material the fastener is threaded into. Also the thread itself plays a role - coarse verse fine depending upon the materials involved. Generally a lot people assume that all you need is a minimum of 1.5 the diameter of the fastener (concerning the depth of engaged threads) for proper clamping force. For effective use of a fastener in a "critical application" this could be a disaster. (But generally a relatively safe assumption when you are talking mild steel alloys of grades 2- 8 used for clamping purposes to hold something in place. I digress - sorry) )

Concerning our bikes: compare the length of engaged threads to the diameter of the fasteners holding togther the two case halfs or even those attaching the side clutch side cover in place. Due to the relatively (but light weight) soft materials associated with the base material; I guessing the related design specied for a minimium engagement of three fastener diameters into the adjacent cover. And we are only talking about something that you torque to what? Maybe 75 in/lbs. (strictly a guess here - look in the manual for Go9's sake prior to tightening)

Best advice I can give is to follow the bike's manual concerning tightening torques. You can find tables for torque values for all kinds of different materials and fasteners. The trouble with using a table of torque values and applying it to a certain size fastener on our bikes is that we may not know the other variables which were considered in the selection of the particular size fastener. (Hope I left you with that appreciation, anyway). i.e. Some times we select a larger fastener than necessary for the required clamping force due to constraints related to the shape of the item. If you come along with a basic thought that -hey I don't have a factory manual but I saw a table of torque values for that size of bolt: then you look up the torque value for that size of bolt: then grab your calibrated torque wrench and torque away and the bolt fails - what the F**k!! - you likely forgot torque values are only one or a number of factors to consider when fastening "stuff together"..

AUTOS -When you are talking automoblies almost every repair manual I've seen will list torque figures for different size and grade fasteners to be used when specific torque values are NOT identified in the manual in the appropriate area. IMO we need to apply the same to our bikes.

http://www.engineersedge.com/fastener_thread_menu.shtml

[RBD]

I have to add this and I will always use anti-seize or oil on all engine fasteners that I assemble:

1) Over-tightening is better than under-tightening. An under-tension bolt failed at 4,900 cycles and an identical bolt that was over-tightened failed at over 6,000,000 cycles! (See book for details.)

2) Worst case torque situation is "dry & unplated" where 50% of the applied torque can be used up overcoming the friction between the bearing surface and the work face and another 40% can be used up overcoming thread friction... leaving only 10% of the torque to pre-load the bolt!

3) Critical tension asseblies (cylinder heads, rod bolts) require special fasteners and each such fastener normally has it own recommended torque value and lubricant to arrive at the correct level of residual stress. (Residual stress is what matters, not how much torque we apply to get it there.)

4) The torque required to produce a given tensile stress varies with plating, lubrication, length of engaged thread, and class of thread fit. We need to achieve an installed tensile stress that is just below the yield strength of the bolt.

Definatly use oil or assembly lube. thats why studs are so much better than bolts. a nut threading onto a stud has far less friction than a bolt threading into the base metal under a torque load. the stud and nut will achieve and hold a truer torque setting and there fore more accurate clamping load. just look at auto engine rod bolts the best way to tighten them is with a stretch guage reagardless of the torque load.

Thank you,
Ron

[IdahoCharley]

Ron - you have and make some great points.

1. "Residual stress is what matters, not how much torque we apply to get it there."

I Agree 100%. The problem is measuring the residual tensile stress in most fasteners once they are installed; unless you can measure elongation or have a strain guage set-up. Use of a torque wrench is however the method most of us use in an attempt to arrive at the designed residual tensile stress clamping force.

2. "We need to achieve an installed tensile stress that is just below the yield strength of the bolt."

I agree 100%

3. ....studs are so much better than bolts. a nut threading onto a stud has far less friction than a bolt threading into the base metal under a torque load. the stud and nut will achieve and hold a truer torque setting and there fore more accurate clamping load"

I agree 100%

4. "Over-tightening is better than under-tightening. "

I agree 100% as long as the fastener's material's maximium elasticity is not exceeded.

5. Worst case torque situation is "dry & unplated" where 50% of the applied torque can be used up overcoming the friction between the bearing surface and the work face and another 40% can be used up overcoming thread friction... leaving only 10% of the torque to pre-load the bolt!

I agree 100%. I just assumed that we were talking of using the specified fasteners for the task and not creating our own out of shop stock material. So I assume the fasteners would be plated to some ANSI or ISO standard. I believe we are in agreement where lubrication would be the most effective also - under the head of the bolt/nut between the load bearing surfaces.

I do hope that we have aided the poor sucker (KDXsean with the original question ) and not confused him. It is better to have an abundance of information, I suppose, than not enough.

This is my last post on this - I will take a sabbatical to allow my fingers to get some feeling back.

[KDXSean]

I've found this discussion quite interesting actually. I am going to use a little anti seize on the cylinder studs though. I did twist off a bolt once when I was changing my handle bars, while using a torque wrench. I always figures the bolt was overstressed from assembly at the factory though. I was just thinking about it and thought I'd get some opinions.

Thanks boys.

[Mark W]

How the air temperature at the time of fastening? I would think that torque would also be affected by the temperature at the time you are reading the torque? different metals reacxt differently to temps and you really couldn't make a table to compensate for this as there would be to many variables. I know that you can calibrate the torque wrench for temperature but not for the way various metals react at various temps.

I am beginning to wonder (amke that I know I'll have to recheck) the torque on my head and cylinder nuts as I did the work in the middle of the winter in Minnesota in an unheated garage.

Never thought of this.

Mark

[bradf]

Mark, you can always go back and re-torque, just hold yer teeth in a "summery" sort of way instead of chattering this time.