Topic: Snapped a HD cylinder head stud on bolt up, why me!!!

[BLUE71TURBO]

 For any special stud or bolt/nut combination call ARP. If they don't have it they will make it.   

[754]

I got a few stockers to test..

[paulages]

I had an APE stud fail on me recently at 18 ft/#.

[scottly]

I got a few stockers to test..

I figured you would. If I had some, I would set up a test with a length of pipe, with bushings that fit into the pipe on either end, to hold the stud straight.
I'm very curious to hear your results... 

[Gaither]

I know nothing and should NOT argue with the experts!

I am certainly NOT attempting to offend nor to start (nor will I enter into) an argument. This is only an opinion that likely serves no useful purpose. Further, I have no desire to change anyone's mind on the matter. Just sharing an opinion here.

However, (for example and if wet or dry is NOT specified) IMHO if a stud (bolt) requires 20 lbs of torque, I fail to see how less torque is correct and ample just because oil is used.

In my admittedly dim view, 20 lbs is 20lbs wet or dry - EXCEPT if dry, I missed the required torque since I am also blindly measuring friction. (Unless all threads are completely clean, I still think friction will vary stud-to-stud -wet or dry.)

Also, in my dim view, (for example, as with a head gasket) if 20 lbs is specified (with or without wet/dry mentioned) I would oil 'em and go (incrementally) to 20 Lbs. If I only go to 18 lbs, IMO, I'm asking for a blown gasket - which actually (in this example) called for 20 lbs.

If the fastener will stand the 20 lbs torque specified (an obvious requirement) why would I stop at 18 lbs just because I oiled the threads? The 18 lbs is NOT 20 lbs and is NOT up to the 20 lb spec.

I admit I am dense. However, I can't see how 18 lbs equals a specified 20 lbs - just because oil is used. Rather, I would think 20 lbs dry would not be as good as 20 lbs wet and due to friction, missed the spec.. IMHO, I would think 20 lbs wet would be required to help insure the life of the more properly sealed and tightly held (example) gasket.

In cases where wet and/or dry torque specs are given, I would, of course, be guided by the specs as listed. Where it isn't specified wet or dry, I'm gonna oil 'em and go the the spec listed - regardless of what the wet/dry chart says. I haven't had a head off in years but I have NEVER broken a head stud (or bolt). But I'm subject to do so as much as anyone.

In the meantime, let us all just be guided by our own judgements and opinions and continue to do this in our own way.

Perhaps I should also add, "peace" and "to each his own".

[MCRider]

(I have googled "torque wet or dry" and variations of such and have read maybe 20- articles. they all agree except a few which invariabley contain no citations and are thus heresay. I'll go with academic style citations over heresay. ie:

No Lube torque value 100%
SAE20 oil reduce by 38%
SAE40 oil reduce by 41%
White grease reduce by 45%
Dry moly film reduce by 52%
Graphite and oil reduce by 55%
 
Pocket Reference - Thomas J Glover
Published by Sequoia Publishing. Littleton Colorado, USA)

What I've gleaned:
When torquing a bolt and nut, the torque is just an easy way to measure what you are really looking for which is "clamping force". When tightening a dry fastener, a lot of the torque goes to overcoming the friction of the threads and does not convert to clamping force. Hence when you wet the fastener, you reduce the torque by the amount of friction which is relieved to get the same clamping force.

The table above indicates the different reduction % used per different lubes.

The real peril then becomes, knowing for sure whether the torque requirement stated is for a dry or wet fastener. One artivcle i crossed had a a cite from the FAA which clearly stated "all aircraft torque values are for clean DRY fasteners".  (emphasis mine) With the caveat implied to adjust torques for the lubricant used. I ran across cites where European specifically MotoGuzzi stated in their manuals, "all torque values are WET" emphasis theirs in this case. There was no indication of wet with what? but nevertheless, the distiction between wet or dry was made.

Undoubtedly there can be all kinds of peripheral arguments about the % reduction etc. but the concept has been proven to me thru my research. Reduce the torque used when lubricating a fastener.

[MCRider]

More cites: from "freelibrary.com"
"Lubed threads reduce run-up friction and could cause you to overtorque."
http://www.thefreelibrary.com/Torque+wrench+tidbits-a0169591051

This has a generic discussion complte with tables for dry and wet applications. You must use the "next" button at the top to access the dry table first, then another "next" for the wet table. Bottom line 20-30% reduction in torque used dry vs wet.
http://www.tpub.com/content/bridges/TM-5-5420-278-24P/css/TM-5-5420-278-24P_385.htm

Ultimately I offer that very few parts are really torque critical and a decent experienced mechanic will know by feel if its tight enough. Exception being head nuts and main bolts. But even there there is leeway and consistency and sequence may be more important, once you get to the zone.

To each their own, I agree.

[fantino]

Hrmm, just wanted to update y'all that I too snapped a HD cylinder stud on my CB500 today. It was somewhere between 15 and 20ft-lbs when it snapped, no more than 20 and tightened in 3 stages, snapped right at the bottom of the top threads.



Kind of a disappointment, to say the least. Luckily it came out pretty easily with a pair of vice grips and a little heat.

[scottly]

What is going on with these HD studs? Are they all breaking off with one or two threads threads left?

[dave500]

not very heavy duty then.probably chinese.

[Retro Rocket]

Mine aren't Chinese and i had one snap as well...

Mick

[dave500]

seems odd?so heavy duty studs are because they have to hold down more force?or not break when you torque them?depending on your wrench i dont think they are accurate at the lower end of the scale,an automatic transmission one is probably more appropiate,mine goes to 120 ft/lbs,starts at 10,,probably a bit heavy for small bike stuff,i do a bit of car stuff aswell though,i err on the lighter side and have had no troubles,head nuts aint wheel nuts!

[kmb69]

First, let me say that I am not a metallurgist but do have quite a bit of experience with heat treated materials and rolled threads. I have read that these HD studs are heat treated PRIOR to rolling the threads. This seems wrong to me because rolled threads are created by plastic deformation of the material. The stud or bolt is machined to a diameter roughly equivalent to the pitch diameter of the desired thread. The thread rolling tool actually compresses the material to form the root of the thread (minor diameter) and the thread crest (major diameter) results from the displaced material that flows outward. I would think this plastic deformation of the heat treated material adversely affects the material properties and leaves surface fractures near the last thread on heat treated material. The fact that they are breaking near the last threads is a good indicator that these threads are not fully formed and may have "fractured" or "cracked" surfaces that propagate the failure. One reason rolled threads are considered to be stronger than cut threads is due to the compressed surface layer and smoother surface finish as opposed to the surface imperfections left by a cutting tool.

I have a subcontract machine shop and machine parts per my Customers' specifications. All of my Customers specify thread rolling on annealed material and heat treatment AFTER the thread rolling process. The softer material more readily "deforms" to the thread rolling tool without fracturing. Also, many of my Customers specify a thread relief diameter so that the thread is fully formed on exit. This area of reduced diameter is obviously weaker than a full diameter section but not necessarily weaker than a full section with a surface crack. The relief diameter is only minimally smaller than the minor diameter of the thread which becomes the effective stud diameter in the threaded section. ARP is probably the expert in this field since they produce most of the high strength studs and rod bolts used in today's racing engines. Big Jay (APE) or Buzz (Dynoman) should be able to shed some light on this issue.

Regarding the torquing issues, the goal is to "stretch" the bolt or stud to a predetermined length well within the ultimate tensile strength of a given fastener material and mating components. It is common to measure the "stretch" of rod bolts with a dial indicator as opposed to the torque value. It is relatively easy to use this method on exposed studs but embedded bolts are a different matter. "Clicker" type torque wrenches are notorious for "losing" their "calibration". Beam type torque wrenches are usually more accurate in my opinion.

Maybe didn't answer any questions, just my 2 cents.

[dave500]

i have both a clicker and a dual signal beam type,i use the clicker for wheel nuts.,even if a torque wrench is out of calbration at least it still gets all the nuts or bolts the same tension.

[Ace]

Well last Sunday I got a package from APE.  It felt a bit heavy so I opened it up and to my surprise I had an entire set of HD studs.  I was surprised as I only wanted one and requested it along with a few other bits and pieces.  APE also charged me for the full set.  That part slipped through the checking and balance machine.  I guess if I did break another one I had a few spare.  Torqued down to 19 ft-Ibs dry or so my torque wrench said.

All is finally together.  A few electrical problems as I put everything into another frame (not bent).  After sorting the electrical problems, bike fired up straight away, no rattles or oil leaks for the moment and I hope it stays that way.

My stud broke about 2-3 threads from the bottom.

Another engine together and the chapter closed.  Oh on a side note, Hondaman gave me some advice before his book was published about drilling extra holes in the cam towers and rocker arm holes for more lubrication.  I did that mod last year and when I pulled it apart 12 months later there was oil all up through the cam etc which was more than before the mod.  I reckon it works.  Thanks HM. 

[paulages]

Hrmm, just wanted to update y'all that I too snapped a HD cylinder stud on my CB500 today. It was somewhere between 15 and 20ft-lbs when it snapped, no more than 20 and tightened in 3 stages, snapped right at the bottom of the top threads.



Kind of a disappointment, to say the least. Luckily it came out pretty easily with a pair of vice grips and a little heat.

mine broke in the exact same place.