Torque Wrench "Cracks"

[Bull]

I have a nearly new Taiwan-made torque wrench that goes to 250 ft lbs. I had it set to 140 to tighten the lugs on a Tahoe. While pulling hard and steady to get the final value for one nut, the wrench made a loud "cracking" sound and gave way. But, when I tried to use it again it did work.

What does it mean when a torque wrench does this? What is happening inside? I've had it happen before, but on older wrenches that I assumed were wearing out. I just bought this one!

Once it happens, is the wrench damaged?

 

[bobcatdan]

I think it maybe more the nut and bolt making the noise. I have a section of SO and Matco torque wrenches and all of them have made funny noises torquing stuff.

 

[Art From De Leon]

I think it maybe more the nut and bolt making the noise. I have a section of SO and Matco torque wrenches and all of them have made funny noises torquing stuff.

I agree.

 

[Bull]

What would happen to a wheel stud or nut in the course of torquing it down to give me the sensation that something has "slipped" while hearing a loud cracking sound?

 

[APEowner]

It's also possible that there's an issue with the ratchet head mechanism.

 

[Skin]

What would happen to a wheel stud or nut in the course of torquing it down to give me the sensation that something has "slipped" while hearing a loud cracking sound?

Probably the pawl in the ratchet head. All my fine tooth ratchets have done something similar from time to time where the ratchet will jump as if something has broken. Its just the pawl jumping then re-engaging.

 

[AV tinker er]

What would happen to a wheel stud or nut in the course of torquing it down to give me the sensation that something has "slipped" while hearing a loud cracking sound?

By chance did you have a 12 pt socket on a 6 pt bolt or nut? I've had a socket continue to round a bolt and I needless to say I was dottin' some cotton at that moment.

I don't think you are referring to the creaking around bolts make when they are tightened, if so a little oil on the threads helps clear that up.

 

[SMKS]

Does this ratchet have a copy of the Proto design for the ratchet head? My HF torque wrench has done that once or twice over the years. In my case, it was the ratchet head skipping a tooth. I suspect the pawl just didn't seat properly for whatever reason and it pops out of place.

Did the sound come from the ratchet head or the mechanism?

I've also had a similar thing happen with my Armstrong Maxx locking flex ratchet. I was in a pinch and forgot to pack a breaker bar, so I was using a jack handle as a cheater. In this instance, I was just overloading it with torque, so it's not exactly the same as the OP's situation.

 

[RCStocker]

The new HF electronic was tested and did very well. It kept its accuracy better than most major brands.
Rember to set it to 0 when finished. It will stretch and not keep its accuracy.

 

[Art From De Leon]

A bit of rust or corrosion on the thread would allow it to momentarially bind up, and release, as it attempts to gall.

A little spray of PB Blaster, Kroil, or any lubricant will make things go on a lot better.

In fact, when I remove the wheels from my trailers and put them inside to keep them out of the weather, I will run a die down the wheel studs after spraying them before reinstalling the wheel assemblies.

 

[cosmik binturong]

The new HF electronic was tested and did very well. It kept its accuracy better than most major brands.
Rember to set it to 0 when finished. It will stretch and not keep its accuracy.

you mean, like, setting the electronic display to zero?

good thing to not stretch that strain gauge too much though...

 

[Outlawmws]

The new HF electronic was tested and did very well. It kept its accuracy better than most major brands.
Rember to set it to 0 when finished. It will stretch and not keep its accuracy.

you mean, like, setting the electronic display to zero?

good thing to not stretch that strain gauge too much though...

Aside from the casual nonsense noted: This has what to do with the OP's question?

 

[nicksnothereman]

I have a nearly new Taiwan-made torque wrench that goes to 250 ft lbs. I had it set to 140 to tighten the lugs on a Tahoe. While pulling hard and steady to get the final value for one nut, the wrench made a loud "cracking" sound and gave way. But, when I tried to use it again it did work.

What does it mean when a torque wrench does this? What is happening inside? I've had it happen before, but on older wrenches that I assumed were wearing out. I just bought this one!

Once it happens, is the wrench damaged?

If you over torque a lug nut it makes a screetching sound. Try it with a lug wrench.

I don't know if that's actually over-torquing your lug nuts though and don't know if that's the issue you have.

 

[mailpup]

What does it mean when a torque wrench does this? What is happening inside? I've had it happen before, but on older wrenches that I assumed were wearing out. I just bought this one!

Once it happens, is the wrench damaged?

Yes, it sounds like your torque wrench broke. It might have been defective. That's what warranties are for. You can try to exchange it under warranty or if that isn't an option, you can try to have it repaired at a torque wrench calibrating/repair station but you'll have to pay for it.

 

[smiffy]

I don't think you are referring to the creaking around bolts make when they are tightened, if so a little oil on the threads helps clear that up.

This would completely defy the whole point of using a torque wrench as by adding oil you are changing the friction values and the torque will be incorrect you are moat likely to over torque but in worst case scenarios the oil can reduce the friction enough to loose the nuts

 

[premierplayer]

This would completely defy the whole point of using a torque wrench as by adding oil you are changing the friction values and the torque will be incorrect you are moat likely to over torque but in worst case scenarios the oil can reduce the friction enough to loose the nuts

correct, torque values are spec'd DRY
unless otherwise noted

adding lube or xxxx changes the value, you'll over tighten, maybe start breaking things by adding lube

 

[premierplayer]

This would completely defy the whole point of using a torque wrench as by adding oil you are changing the friction values and the torque will be incorrect you are moat likely to over torque but in worst case scenarios the oil can reduce the friction enough to loose the nuts

correct, torque values are spec'd DRY
unless otherwise noted

adding lube or xxxx changes the value, you'll over tighten, maybe even start breaking things by adding lube

 

[CalsXS2]

Does it do this every time you hit final torque.

Do you have a clicker style torque wrench.

 

[Bull]

This is a clicker style and the brand is Titan. I've never had the guts out to see the design of the internals. On the outside it does not look like a Proto pearhead copy.

I was using a 21 or 22 mm 6-point socket. Lug stud threads were dry. But, I have heard that if you oil them or use anti-seize, you decrease the required torque by 30% or so to compensate. I don't know if that is correct.

The wrench does not do this each time it hits final torque. It's only done it once so far.

The explanation involving the pawl slipping sounds plausible to me.

 

[AndrewV]

I personally think it was skipping teeth bull.
You said you torqued dry, on a 6pt socket.
Unless the internals had a catastrophic failure, i don't see any other way.

Is the housing still intact, no cracks, or stress marking across it? If no on that, i feel the ratcheting mech, was just jumping teeth still.

 

[Outlawmws]

Bull, assuming the wrench is like the Titan one below, with a std Ratchet head, I'd agree its was just a ratchet pawl slipping. It could have been the pawl simply didn't seat fully once, it could be something wrong with the gear on that tooth (again, assuming a simple low count gear), it could have been debris inside holding up the pawl...

The ratchet head can be disassembled, cleaned, inspected and re-lubed, in situ, and it won't affect the torque measurements at all. in any case I've had that happen a time or two over the years, and I don't think you have a serious problem.

 

[CJKaz]

This is a clicker style and the brand is Titan. I've never had the guts out to see the design of the internals. On the outside it does not look like a Proto pearhead copy.

I was using a 21 or 22 mm 6-point socket. Lug stud threads were dry. But, I have heard that if you oil them or use anti-seize, you decrease the required torque by 30% or so to compensate. I don't know if that is correct.

The wrench does not do this each time it hits final torque. It's only done it once so far.

The explanation involving the pawl slipping sounds plausible to me.

From one of several threads about torque compensation for lubricant on threads:

Re: Torque number with Anti-seize
The torque required for a bolted joint design comes from a long string of calculations, but boils down to a simple linear equation.

T = Wp x K x dn
Where T=torque; Wp=fastener preload; K=torque coeff; dn=diameter

The factor that changes with dry vs lubricated fasteners is the "torque coefficient" and is published for a variety of cases. Various values exist, mine are taken from DuPont Engineering Specification (10 pages of calcs). Examples:

Dry steel fasteners: K=0.20
Lightly oiled steel: K=0.15
Cad Plated: K=0.14
Anti Seize on steel: K=0.13 (as published by Bostik for their Never Seez products)
Graphite & mineral oil: K=0.10

Using Never Seize versus dry uncoated steel, multiply the specified torque by 0.65.

A very light coating on the threads only to prevent corrosion and/or galling is all that's needed. As is the case with most Anti Seize applications, a little goes a long way.

 

[AV tinker er]

This would completely defy the whole point of using a torque wrench as by adding oil you are changing the friction values and the torque will be incorrect you are moat likely to over torque but in worst case scenarios the oil can reduce the friction enough to loose the nuts

Lug stud threads were dry. But, I have heard that if you oil them or use anti-seize, you decrease the required torque by 30% or so to compensate. I don't know if that is correct.

Someone understood where I was going with that statement.

I've heard figures from 15% to 30%. I did a search and came up with nothing I would trust (although the above post seems to have it figured out) in a very critical situation but for lug nuts I'd be okay with using a reduction in that range.

 

[CJKaz]

Those calculations and values are directly from a corporate engineering standard as stated. Not unique to that company, standard engineering formulas, albeit not easily found these days with all the conjecture and "I read this on the internet" that abounds today. You typically need to dig deeper to find the root of the information (engineering principles).

Equipment manufacturer's sites often have good technical sections that give the details of the calculations.

As to the self loosening effect of lubricated fasteners, research topics like "Junkers test". There are extensive tests performed by manufacturers. For example Teflon® coated fasteners are used in extreme services. You can bet that testing was performed to ensure a flange fastener won't loosen in a toxic chemical service (hint, they don't if properly designed & torqued).