Recommended Torque Limits by Drive Size

[The Critic]

This video is from 2018 so I assume the info is current.

Skip to 3:30.

According to Snap-On, these are the maximum recommended working torque by drive size:

1/4 (under-dash): 28 ft lbs
3/8 (engine bays): 80 ft lbs
1/2 (under-vehicle): 330 ft lbs

The numbers for 1/4 and 3/8 seem low. Thoughts?

 

[Greasymechtech]

My limits depend on the torque wrench, and whether the socket cracks...

So, it depends on the tool and not the youtube video.

 

[LDB]

I have to walk out the door in 2 minutes so I haven't watched the video yet but I'd think SO would know the limits on their tools. If they say so I guess it's true.

 

[Trav]

This video is from 2018 so I assume the info is current.

Skip to 3:30.

According to Snap-On, these are the maximum recommended working torque by drive size:

1/4 (under-dash): 28 ft lbs
3/8 (engine bays): 80 ft lbs
1/2 (under-vehicle): 330 ft lbs

The numbers for 1/4 and 3/8 seem low. Thoughts?

Almost 38Nm for 1/4. 108Nm for 3/8 and 447Nm for 1/2 is a good number and not low. In practice I generally don't go more than 35Nm for 1/4, 90Nm for 3/8 and 400Nm for 1/2 after that it is 3/4 drive.
Even though they may make a 18" 3/8 drive ratchet does not mean it can take more torque than a 7" 3/8 both are going to fail at around 225 lb.ft, it is for better access only. Their 80 lb.ft is working torque is so it does not over stress the tools. These youtube video's stressing them until they break is meaningless nonsense.

 

[CR94]

For square-drive tools of different sizes but exactly similar geometry and identical materials, torsional strength theoretically should be proportional to the cube of nominal square size (or any other linear dimension). For example, ½" should be 2³=8 times as strong as a similar ¼" component, or (4/3)³=2.37 times as strong as an otherwise similar 3/8" component. The numbers quoted above don't follow that logic very well. Who knows why?

Wrenches are supposed to meet standards for strength and fit, for example U.S. Federal Specification GGG-WW-641E or ANSI B107.10M (which are both old, and may have been superseded by updated versions).

Perhaps the highest torque I ever put on a ½" drive handle was by standing on a flex-handle with a short pipe extension, maybe roughly 250 ft-ib., trying to loosen grossly overtightened lug nuts that were supposed to be 65 to 80 ft.-lb.