anti seize question

[Bill M.]

Re: anti seize question

That's why virtually ALL critical torque-control tools in automotive plants, especially multiple-spindle nutrunners in critical applications like lug nuts, cylinder heads, main and rod caps, etc. aren't air tools any more; they're all computer-controlled electric DC motors with both torque and angle control sensors, with precisely-controlled constant spindle rpm during rundown. Every activation of each spindle is computer-monitored and recorded to ensure compliance with specifications.

And the torque specification is established for a critical joint by running many (12 is typical to allow accurate statistical analysis) of the joints with all production-level parts in the fastener lab. using clamp load transducers to determine the optimum torque.

[Joe L.]

Re: anti seize question

Michael,

Its very difficult and expensive to actually measure stretch/clamp-load during tightening, although it is done. As John noted, most control tools utilize some easily measurable dynamic feedback from the tightening process ie: torque, angle, and/or time to estimate stretch and control the tool shut-off.

There are hundreds of different algorithms that use those measurements to estimate where the fastener is in the tightening process, then shut off the tool at the ideal place. Many of those are very successful without the difficultly or expense inherent in actual measurement of stretch.

There are also lot of arguments about where you'd like to end up after tightening, ie: at yield, just beyond yield, 90% of yield, etc.

Most people think of fastening as very simple, it is not, every attachment is just a bit different.

Michael------


With the majority of fastener situations, I don't see how bolt stretch can be measured. It can be measured, of course and for example, in the case of connecting rod bolts but in the case of most bolts, only one end of the bolt (head) is accessible.

[Don H.]

Re: anti seize question

So,,,,,,,

Inquiring minds want to know.....

The consensus is that it IS OK to use anti-seize on the wheel studs so lug nuts won't gall ? (even though some said they would not do it?)

[Clem Z.]

Re: anti seize question

my answer is,if it was necessary GM would do it at the factory

[Jim L.]

Re: anti seize question

The consensus is that it IS OK to use anti-seize on the wheel studs so lug nuts won't gall ?

My "take away" is this:

1. The original torque specs are for dry threads.

2. The use of any thread lubricant (such as antiseize) reduces the required torque.

3. No one knows for certain by how much to reduce the torque to ensure the wheel studs don't become over tightened.


Therefore, the "safe" conclusion is to continue to torque the studs dry and to do so to the dry torque spec.

That's my conclusion and I'm stickin' to it.

Jim

[Michael H.]

Re: anti seize question

So,,,,,,,

Inquiring minds want to know.....

The consensus is that it IS OK to use anti-seize on the wheel studs so lug nuts won't gall ? (even though some said they would not do it?)

I think someone mentioned earlier in this thread that it would probably be safe to go with lubricated threads but stay with the low side of the torque spec. I think I agree with that.

I don't remember the formula for the reduction factor and I can't find it now. Been looking for it for two days. It's here somewhere in all this rubble.

[Dick W.]

Re: anti seize question

my answer is,if it was necessary GM would do it at the factory

They did not drive the vehicle in salt and then have to remove the wheels. As long as the wheels would torque and stay on to get out the door, that is all that was required by them

[Joe L.]

Re: anti seize question

My "take away" is this:

1. The original torque specs are for dry threads.

2. The use of any thread lubricant (such as antiseize) reduces the required torque.

3. No one knows for certain by how much to reduce the torque to ensure the wheel studs don't become over tightened.


Therefore, the "safe" conclusion is to continue to torque the studs dry and to do so to the dry torque spec.

That's my conclusion and I'm stickin' to it.

Jim

Jim------


The "other side of the coin":

When GM first installed the lug nuts, the nuts, the studs and the wheels were new and free from corrosion. In service, lug nuts, studs, and wheels often suffer from corrosion or other deformation damage. Ever try to run a well used lug nut down a well used stud by hand? Usually, it can't be done even if one were to wire brush the threads of the nuts and studs. I attribute this to some sort of "naturally occurring" thread damage or deformation. So, when one torques a lug nut in the referenced circumstances, the actual torque applied is less than the torque wrench setting (and the lug bolt stretch is consequently less than the stretch that would occur if the as-new, full torque was applied).

I would much rather have a fastener system somewhat over-torqued than have the system under-torqued as would result in the above-described circumstances. My feeling has always been than the lubrication provided by the anti-seize compound APPROXIMATELY "cancels out" the increased friction in the system due to corrosion and deformation. Beyond that, in all my years and having removed and re-installed thousands of lug nuts, I have never broken one-----not a single one.

[Michael G.]

Re: anti seize question

The answer is: maybe.

I don't have the original prints, but I'd guess the studs were phos and oil and the nuts were zinc coated. If someone can verify that, I'd be glad to give you an expert opinion on the effect of anti-seize. I might even be inspired to do a test.

[Ronald L.]

Re: anti seize question

Michael,

On the studs, they were heat treated, oil quenched and annealed. I don't know that they ever got phos, not when I was there and Zn on the nuts (from NOS examples).

[Jim L.]

Re: anti seize question

Jim------


The "other side of the coin":

When GM first installed the lug nuts, the nuts, the studs and the wheels were new and free from corrosion. In service, lug nuts, studs, and wheels often suffer from corrosion or other deformation damage. Ever try to run a well used lug nut down a well used stud by hand? Usually, it can't be done even if one were to wire brush the threads of the nuts and studs. I attribute this to some sort of "naturally occurring" thread damage or deformation. So, when one torques a lug nut in the referenced circumstances, the actual torque applied is less than the torque wrench setting (and the lug bolt stretch is consequently less than the stretch that would occur if the as-new, full torque was applied).

I would much rather have a fastener system somewhat over-torqued than have the system under-torqued as would result in the above-described circumstances. My feeling has always been than the lubrication provided by the anti-seize compound APPROXIMATELY "cancels out" the increased friction in the system due to corrosion and deformation. Beyond that, in all my years and having removed and re-installed thousands of lug nuts, I have never broken one-----not a single one.

Joe, thanks for responding.

This wheel stud question apparently has no good answer.... too many imponderables....

.....surface treatment of the studs/nuts by the manufacturer,

.....GM's intent with the torque spec (get it out the door? save the customer from him/herself? prevent lawsuits? keep the customer safe?),

.....the effect of any lubricant on the required torque, and the difficulty of doing "good science" to discover the true effect

......the prior history of the stud/nut combination (are they new because of restoration? did some gorilla previously over tighten the lug nut? have the studs been weakened by corrosion?)


My own take on the situation runs along these lines:

- a wheel stud that has been over tightened to the point of permanent deformation even once is in danger of imminent failure.

- there is no measurement you can make to determine if the above has happened.

- if I encountered a stud/nut combination that could not be spun on/off by hand, I'd conclude the threads had been deformed and replace same.

- if one knows for absolute certain that the studs/nuts have never ever been overtightened, then a "safe" approach is to torque dry, test drive, re-check torque, repeat until a stable torque reading can be obtained.

- if the studs/nuts are new, I would go a step further and first "condition" the threads by doing several tighten/loosen cycles (minimum of 5, maximum of as many as my patience allows).


Like you, I've never broken a wheel stud nor have I had one come loose. Since my methodology differs slightly from yours, it reinforces what I wrote at the beginning..... no good answer, too many imponderables.

Jim

[William F.]

Re: anti seize question

Jim,
I agree with you. Long time GM chassis specialist told me lug nuts go on dry. Can be mischief if you lube an application and torque to dry specs. How do I know?Once I was going to be precise and put anti-sieze on machine screws holding Holley throttle body to main body, torqued to specs(dry specs) and pulled threads right out of carb body.

[Paul J.]

Re: anti seize question

Therefore, the "safe" conclusion is to continue to torque the studs dry and to do so to the dry torque spec.

That's my conclusion and I'm stickin' to it.

Jim

I agree, Jim. I've torqued thousands of lug nuts dry over the past 39 years and I've never had any issues. There are some good arguments here for using lubricants and anti-seize, but no concrete data. I'm stay'n dry and using what I know works. If it ain't broke don't fix it.

Paul

[Michael H.]

Re: anti seize question

I agree, Jim. I've torqued thousands of lug nuts dry over the past 31 years and I've never had any issues. There are some good arguments here for using lubricants and anti-seize, but no concrete data. I'm stay'n dry and using what I know works. If it ain't broke don't fix it.

Paul

Yup, I agree too. And metal fatigue is another reason why I torque to the minimum torque spec. on 40 year old wheel studs.
Is a fastener that has been torqued to it's stretch range 50 times as durable as a new one that has never been torqued? Absolutely not.
Now add the rust factor. We know that rust has quite an effect on a fastener integrity.
And if the stud/nut is lubricated, that should bring the total torque value down also.

GM clearly states that somewhere between 55-65 ft lbs for my cars is the correct number so that means there's absolutely nothing wrong with 55 ft lbs.

[Michael G.]

Re: anti seize question

Jim, While I tend to agree that there are a lot of variables, I think there are probably some general recommendations that can be made, once the metalurgy, materials, and finishes involved are clarified. Given the surface finishes and possible corrosion involved here, it is likely that a medium-friction anti-sieze is a good idea on used studs. With further study, I'm willing to try to come up with some generalizations.

In regard to your comments on this:

1. Millions of fasteners are deliberately tightened into "permanent yield" every day. This is a common tightening strategy. They are not in danger of imminent failure. In essence, slightly yielding a fastener is not a problem.

2. Significantly yielded fasteners are detectable through measurement. The pitch of a yielded part will be longer in the first threads beyond the nut. A common thread "go" gage can detect this distortion.

3. Rust, nicks, and dirt can make threads fail to spin freely, without any deformity being present in a used thread.

4. A stud that will accept a 'go" gage and also achieve and hold the design torque is not going to fail in normal service, even if it has been yielded slightly.

4. While freely spinning a nut all the way onto a stud (once) prior to torquing will likely improve the consistency of the torque tension relationship, multiple loaded assemblies or "Conditioning" a thread alters its friction significantly and will not re-create the desired design condition.

Ron, It would surprise me if the studs were not oiled. Additionally, wheel studs in the 70's and 80's were case hardened, it'd be nice to know if those in the the 60's were also. It would also be nice to see the stud prints to see the actual GM specs.