A pound-foot (lb⋅ft), abbreviated from pound-force foot (lbf · ft), is a unit of
torque representing one
pound of force acting at a perpendicular distance of one
foot
The foot (: feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is an organ at the terminal part of the leg made up o ...
from a pivot point. Conversely one foot pound-force (ft · lbf) is the
moment about an axis that applies one pound-force at a radius of one foot.
Unit
The value in
Système International (SI) units is given by multiplying the following exact factors:
:One
pound (mass) =
:
Standard gravity = 9.80665 m/s
2
:One
foot
The foot (: feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is an organ at the terminal part of the leg made up o ...
= 0.3048 m
This gives the exact conversion factor:
:One pound-foot =
newton metre
Newton most commonly refers to:
* Isaac Newton (1642–1726/1727), English scientist
* Newton (unit), SI unit of force named after Isaac Newton
Newton may also refer to:
People
* Newton (surname), including a list of people with the surname
* N ...
s.
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).
[ In most US industrial settings, the torque ranges are given in ft-lb rather than lbf-ft.] 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 . It is commonly used on
torque wrenches and
torque screwdrivers for setting specific fastener tension.
See also
*
Kilogram metre (torque) (kgf⋅m)
References
{{United States Customary Units
Units of torque
Imperial units
Customary units of measurement in the United States
de:Foot-pound