Pound-foot (torque)
| pound-foot | |
|---|---|
| Unit system | British Gravitational System, English Engineering Units |
| Unit of | Torque |
| Symbol | lbf⋅ft or lb-ft |
| Conversions | |
| 1 lbf⋅ft in ... | ... is equal to ... |
| SI units | ≈ 1.355818 N⋅m[1] |
| Gravitational metric system | ≈ 0.1382550 kgf⋅m |
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 from a pivot point.[2] 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) = 0.45359237 kilograms[3][4]
- Standard gravity = 9.80665 m/s2[4]
This gives the exact conversion factor:
- One pound-foot = 1.3558179483314004 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.[6]
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).[7][8] 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 1⁄12 lbf⋅ft (0.1129848 N⋅m). It is commonly used on torque wrenches and torque screwdrivers for setting specific fastener tension.
See also
- Kilogram metre (torque) (kgf⋅m)
References
- ↑ "Appendix B.9: Factors for units listed by kind of quantity or field of science". NIST Guide to the SI. National Institute of Standards and Technology. September 7, 2016. https://www.nist.gov/pml/nist-guide-si-appendix-b9-factors-units-listed-kind-quantity-or-field-science.
- ↑ Pickerill, Ken (2009). Today's Technician: Automotive Engine Performance Classroom Manual and Shop Manual (5th ed.). Cengage Learning. pp. 50–51. ISBN 978-1111782382. https://books.google.com/books?id=7SEGAAAAQBAJ&pg=PA20.
- ↑ United States National Bureau of Standards (1959-06-25). "Notices "Refinement of values for the yard and the pound"". http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf.
- ↑ 4.0 4.1 Howard Ludwig (Mar 3, 2017). "What is the relation between pounds of force and pounds as a measurement of mass?". https://www.quora.com/What-is-the-relation-between-pounds-of-force-and-pounds-as-a-measurement-of-mass.
- ↑ Collins, Joseph B. (2009), "OpenMath Context Dictionaries for SI Quantities and Units", in Carette, Jacques; Dixon, Lucas; Coen, Claudio Sacerdoti et al., Intelligent Computer Mathematics: 16th Symposium, Calculemus 2009, 8th International Conference, MKM 2009, Grand Bend, Canada, July 6-12, 2009 Proceedings, 5625, Springer Science & Business Media, p. 260, ISBN 978-3642026140, https://books.google.com/books?id=IKNmax4dZ70C&pg=PA260
- ↑ Arthur Mason Worthington (1900). Dynamics of rotation : an elementary introduction to rigid dynamics (3rd ed.). Longmans, Green, and Co.. p. 9. https://archive.org/stream/dynamicsofrotati00wortuoft#page/8/mode/2up.
- ↑ "Dial Torque Wrenches from Grainger". Grainger. 2020. https://www.grainger.com/category/tools/hand-tools/wrenches/torque-wrenches-accessories/dial-torque-wrenches. In most US industrial settings, the torque ranges are given in ft-lb rather than lbf-ft.
- ↑ Erjavec, Jack (22 January 2010). Manual Transmissions & Transaxles: Classroom manual. pp. 38. ISBN 978-1-4354-3933-7.
de:Foot-pound
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