smolenr

In the attached chart, the torque numbers are supposed to be N-M. However 12 N-m is approximately 106 inch pounds, which is a higher torque than the lug nuts on my car! I called Shimano customer service and they were adamant that it is all N-m. Is there anyone on this site that can confirm? Thanks

smolenr

You're absolutely right! My bad, sorry! Lug nuts are in ft-lb.

ScottCommutes

Ft-lbs are intuitive - one foot pound is the same as one pound at the end of a one foot lever (or wrench). Inch pounds are ridiculous, especially with fractional foot pounds. Often, inch pounds are used deceptively to advertise a 12x more impressive looking torque number than ft-lbs.

Also, a ft-lb is the same as a lb-ft, except it's not.

Bill Kapaun

https://www.onlineconversion.com/

13ollocks

How is ft-lb not the same as lb-ft? - they're both the product of length and force, and product is commutative (AxB = BxA)

Polaris OBark

Cross products don't commute. In fact, they anti-commute: r X p = - p x r

The reason for this is that the cross or "vector" product is really a second-rank antisymmetric tensor; its pseudo-vector behavior is an artifact of 3D space.

To get back to Bob S's question:

The units seem most sensible if they are N x m.

ScottCommutes

That's what makes it so weird. I believe that one is torque and the other is essentially resistance to torque. I would have to consult Google to get you a more scientific answer, but there really is a time and place to use one set of units or the other - even if they work out to the same thing.

Tusk

lb-ft bothers me to no end when I hear it. It is ft-lb dadgummit.

and we use in-lb all the time. Did you know that the NEC has recommended torque values for almost every electrical fastener?

ScottCommutes

Thirty inch pounds is exactly 2.5 foot pounds. Thirty-one inch pounds is really close to 2.6 foot pounds, and so on. I don't see the need for a special unit just for low values - it just confuses people in the middle-range values where 20 foot pounds is 240 inch pounds.

Tusk

Mid range - yep. They all have their place

We have torque screwdrivers where the range is 5-20 in-lbs.....
And fasteners where the designer specified torque of a 1" A325 bolt requires a 600 ft-lb wrench and a 3:1 multiplier. Or a hydraulic wrench calibrated based on hydraulic pressure.

smd4

Glad we never needed torque wrenches in the shop.

Bill Kapaun

In the shipyard when torquing large steam lines (like aircraft carrier size) they would often use a chain fall on the handle.