Buttress thread
Buttress thread forms, also known as sawtooth thread forms
Buttress thread characteristics
The buttress thread form is designed to handle axial thrust applied principally in one direction. The load-bearing thread face is perpendicular or at a slight slant (usually no greater than 7°) to the screw axis.
Buttress threads have often been used in the construction of artillery, particularly with the screw-type breechblock.[2] They are also often used in vises, because great force is only required in one direction.[4]
It is obvious on inspection that a buttress thread with perpendicular face, operating in a split nut, generates minimal disengagement force when tightened in the normally loaded direction, and thus it is possible to derive quick release devices to, for example, allow rapid repositioning of the movable jaw of a vise without having to rotate the screw by many turns. A screw profile, such as acme, where the thrust face is not perpendicular to the axis, generates a significant disengagement force on a split nut, therefore a more robust controlling mechanism would be required. Quick release vices are readily available. It is not known whether any of them are currently using buttress screws. An expired patent[5] for a clamp using a buttress thread exists and one article[6] describes a vise whose screw thread is disengaged by reverse rotation, which is likely to use a buttress thread, however no currently manufactured devices of that nature have been found at this time (October 2018).
Types
The image gallery below shows some of the types of buttress threads.
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Simple buttress thread form[7]
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The ANSI 45°/7° buttress thread form[8]
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The British 45°/7° buttress thread form[9]
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The 45°/5° buttress thread form[7]
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The 30°/3° German "Sägegewinde" (saw tooth) buttress thread form[7]
Mechanics
Buttress thread in oil field tubing
In oil field tubing, buttress thread is a pipe thread form designed to provide a tight hydraulic seal. The thread form is similar to that of
See also
References
- ^ CN101571035B - Sawtooth thread of drill pipe joint - Google Patents
- ^ a b French, Thomas Ewing (1918-01-01). A Manual of Engineering Drawing for Students and Draftsmen. McGraw-Hill book Company, Incorporated.
- ^ US patent 5127784, David Eslinger, "Fatigue-resistant buttress thread", issued 1992-07-07
- ^ a b Bhandari, p. 204.
- ^ "US3599960A - Screw clamp". Google Patents. Archived from the original on 3 Apr 2024.
- ^ "What is a quick-release feature?". Wonkee Donkee Tools. Archived from the original on Apr 16, 2023.
- ^ a b c Oberg, p.1817
- ^ Oberg, pp. 1819–1820.
- ^ Timings, p. 127.
- ^ US patent 6893057, M. Edward Evans, "Threaded pipe connection", issued 2005-05-17 Figure 6.
Bibliography
- Barnwell, George W. (1941), The new encyclopedia of machine shop practice, Wm. H. Wise & Company.
- Bhandari, V B (2007), Design of Machine Elements, Tata McGraw-Hill, ISBN 978-0-07-061141-2.
- Oberg, Erik; Jones, Franklin D.; Horton, Holbrook L.; Ryffel, Henry H. (2000), ISBN 0-8311-2635-3.
- Timings, Roger Leslie (2005), Newnes Mechanical Engineer's Pocket Book (3rd ed.), Newnes, ISBN 978-0-7506-6508-7.