The buttress thread form refers to two different thread profiles. One is a type of leadscrew and the other is a type of hydraulic sealing thread form. The leadscrew type is often used in machinery and the sealing type is often used in oil fields.
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Buttress thread in machinery
In machinery, the buttress thread form is designed to handle extremely high axial thrust in one direction. The load-bearing thread face is perpendicular to the screw axis.[1] or at a slight slant (usually no greater than 7°)[2] The other face is slanted at 45°. The resulting thread form has the same low friction properties as a square thread form but at about twice[citation needed] the strength due to the long thread base. This thread form also is easy to machine on a thread milling machine, unlike the difficult to machine square thread form. It can also compensate for nut wear using a split nut, much like the Acme thread form.[3]
Buttress threads have often been used in the construction of artillery, because the thread can withstand the axial load placed on it when the powder charge explodes.[citation needed] They are also often used in vices, because great force is only required in one direction.[3]
Types
The image gallery below shows some of the types of buttress threads.
 Simple buttress thread form[4] |
 The ANSI 45°/7° buttress thread form[5] |
 The British 45°/7° buttress thread form[6] |
 The 45°/5° buttress thread form[4] |
 The 33°/3° German "Sägegewinde" (saw tooth) buttress thread form[4] |
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 Acme thread[7][8] the force is transmitted almost parallel to the axis and thread is about the same strength as standard v threads.
See also
References
Notes
- ^ Barnwell, p. 163.
- ^ US5,127,784 (1992-07-07) David Eslinger, Fatigue-resistant buttress thread.
- ^ a b Bhandari, p. 204.
- ^ a b c Oberg, p.1817
- ^ Oberg, pp. 1819–1820.
- ^ Timings, p. 127.
- ^ US6,893,057 (2005-05-17) M. Edward Evans, Threaded pipe connection. Figure 6.
- ^ Oil field glossary entry for buttress thread
Bibliography
- Barnwell, George W. (1941). The new encyclopedia of machine shop practice. Wm. H. Wise & Co..
- Bhandari, V B (2007), Design of Machine Elements, Tata McGraw-Hill, ISBN 9780070611412, http://books.google.com/books?id=f5Eit2FZe_cC.
- Oberg, Erik; Jones, Franklin D.; Horton, Holbrook L.; Ryffel, Henry H. (2000), Machinery's Handbook (26 th. ed.), New York: Industrial Press Inc., ISBN 0-8311-2635-3.
- Timings, Roger Leslie (2005), Newnes Mechanical Engineer's Pocket Book (3rd. ed.), Newnes, ISBN 9780750665087, http://books.google.com/books?id=IZdDk1cMlLcC.
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