 Pound-foot (torque)
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Pound-foot Torque
pound-foot
Unit systemBritish Gravitational System, English Engineering Units
Unit ofTorque
Symbollbf?ft or lb-ft
Conversions
SI units
Gravitational metric system? 0.1382550 kgf?m

A pound-foot (lbf?ft) is a unit of torque representing one pound of force acting at a perpendicular distance of one foot from a pivot point. Conversely one pound-foot is the moment about an axis that applies one pound-force at a radius of one foot.

The value in SI units is given by multiplying the following approximate factors:

One pound (force) = 4.448 222 newtons
One foot = 0.3048 m

This gives the conversion factor:

One pound-foot = 1.35582 newton metres.

The name "pound-foot", intended to minimize confusion with the foot-pound as a unit of work, was apparently first proposed by British physicist Arthur Mason Worthington.

Despite this, in practice torque units are commonly called the foot-pound (denoted as either lb-ft or ft-lb) or the inch-pound (denoted as in-lb). Practitioners depend on context and the hyphenated abbreviations to know that these refer to neither energy nor moment of mass (as the symbol ft-lb rather than lbf-ft would imply).

Similarly, an inch-pound (or pound-inch) is the torque of one pound of force applied to one inch of distance from the pivot, and is equal to 112 lbf?ft (0.1129848 N?m). It is commonly used on torque wrenches and torque screwdrivers for setting specific fastener tension.

This article uses material from the Wikipedia page available here. It is released under the Creative Commons Attribution-Share-Alike License 3.0.