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Is it N-M or Inch Pounds?

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Is it N-M or Inch Pounds?

Old 02-22-24, 10:56 AM
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Is it N-M or Inch Pounds?

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
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Old 02-22-24, 11:14 AM
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You're absolutely right! My bad, sorry! Lug nuts are in ft-lb.
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Old 02-22-24, 11:35 AM
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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.
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Old 02-22-24, 12:17 PM
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https://www.onlineconversion.com/
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Old 02-22-24, 01:51 PM
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Originally Posted by 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.
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)
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Old 02-22-24, 02:32 PM
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Originally Posted by 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)
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.
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Old 02-22-24, 03:31 PM
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Originally Posted by 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)
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.
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Old 02-22-24, 03:49 PM
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Originally Posted by 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.
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?
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Old 02-22-24, 04:28 PM
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Originally Posted by Tusk

and we use in-lb all the time.
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.
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Old 02-22-24, 05:33 PM
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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.
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Old 02-22-24, 06:21 PM
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Glad we never needed torque wrenches in the shop.
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Old 02-22-24, 06:33 PM
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Originally Posted by 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.
In the shipyard when torquing large steam lines (like aircraft carrier size) they would often use a chain fall on the handle.
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