max torque on 3/8" square drive tools?

[Vintage Veloce]

I just broke a 3/8" drive socket extension.


I was torquing wheel lug nuts to 98 lb-ft (133Nm). I was using a 1/2" drive torque wrench but as I only have 3/8" drive sockets I was using an adapter down to the 3/8" extension. I had noticed a bit of twist happening and then on about the 10th lug nut it broke.
It was actually a happy occurrence, as at first I thought I had stripped the lug nut. The extension is much more easily replaced!

Closer inspection shows the extension was unbranded... all my other socket tools are Williams and Craftsman USA so I don't know how that got in there. ;-)

At any rate, it made me think... what is the highest torque for 3/8" drive tools?

(Oh, I did go back and confirm all the lug nut torques with a solid name brand extension that didn't twist.)

 

[BTL-A4]

Have a look here:

What is the maximum torque a 1/2 drive can withstand?

I just broke two 3/8 in. extensions trying to crack an underdrive pulley loose (specs say the pulley is at 130 ft-lbs, but it feels much higher than that). This begs the question: are there standard

mechanics.stackexchange.com

Seems to vary by brand, and depends on the quality. I broke an old Harbor Freight breaker bar on my lug nuts. The damn thing flew apart. They did give me a new one, though. It was so old it didn't have any HF markings, but I mentioned that I got it when HF was actually in San Pedro, down by the harbor.

It seems you used the wrong tool. I bought 1/2 drive sockets for my lug nuts.

You now have an excuse to buy some tools!

 

[Fedwrench]

I think the ANSI standard for 3/8 drive is 150 foot pounds.

I would recommend buying a deep 1/2 drive socket in your lug nut size to use on your wheels. They aren't expensive.

 

[Vintage Veloce]

Yeah, I ordered a Williams 1/2" drive 21mm socket and extension.
But I occasionally but rarely bump into other things that exceed the 75 ft-lb rating on my regular torque wrench and then I break out my big 150 ft-lb torque wrench. But It's so rare (once a year?) that I haven't bought a full 1/2 socket set. Heck, I was only checking the wheel torque on the truck because I just bought it and don't trust dealers!
At any rate... I think I'm going to mostly blame the cheap no-name extension.

 

[corn chip]

blank with no marking i think no question its chinese **** for sure. i wonder how it even made it to the tenth lug

 

[AdAstra]

Interestingly, per ASME B107-110 the 3/8 extensions only need to be proof loaded to 100 lbf•ft. The ratchets are proof loaded at 150 ft•lbf.

ISO 3316 is more uniform where these go to the same 202 N•m (149 lbf•ft) as the ratchets they will generally be used with.

So your usage might have exceeded its design value if it was only designed to meet ASME.

 

[General Geoff]

as a rule of thumb, I won't use 3/8" drive for anything requiring more than ~60 lb-ft unless a 1/2" socket and ratchet won't fit.

 

[justtools]

blank with no marking i think no question its chinese **** for sure. i wonder how it even made it to the tenth lug

I hope that isnt the case. I just bought a set of unmarked extensions. the man swore they were snap ons made for the Goverment. I paid a premium for them because I felt they must be quite rare!!!

 

[Cruzan80]

as a rule of thumb, I won't use 3/8" drive for anything requiring more than ~60 lb-ft unless a 1/2" socket and ratchet won't fit.

Funny how I have a 3/8 digital torque wrench that is certified 20-100 lb-ft...
And yes, you have heard of the name.

 

[Neggy]

ANSI standards are not law.

There are all sorts of Chinesium products in the world without the benefit of an ANSI standard design

There is all sorts of stuff in the world that exceeds ANSI standards too

It's a poor workman that blames his tools

 

[bonneyman]

About a 36" cheater pipe. You need more torque than that, get a bigger drive size!

 

[Ricky Joe]

Yeah, I ordered a Williams 1/2" drive 21mm socket and extension.
But I occasionally but rarely bump into other things that exceed the 75 ft-lb rating on my regular torque wrench and then I break out my big 150 ft-lb torque wrench. But It's so rare (once a year?) that I haven't bought a full 1/2 socket set. Heck, I was only checking the wheel torque on the truck because I just bought it and don't trust dealers!
At any rate... I think I'm going to mostly blame the cheap no-name extension.

I don’t trust dealers, either, and very few other mechanics. I would be just as afraid that the lugs were overtightened as I would that they were loose. Probably more so.
Even good tools break. S-K seems especially vulnerable, but Snap-On, Craftsman, Bonney, Walden, Proto, Herbrand, Vlchek, a few more, all have representatives in my scrap pile, to be used to weld to make tools. There is also a Craftsman extension broken cleanly.

 

[Vintage Veloce]

I would be just as afraid that the lugs were overtightened as I would that they were loose. Probably more so.

This. I loosened them all before tightening. A couple on the rear did seem too tight. I needed my breaker bar and pipe extension.