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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 twicecitation 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 form4 |
 The ANSI 45°/7° buttress thread form5 |
 The British 45°/7° buttress thread form6 |
 The 45°/5° buttress thread form4 |
 The 33°/3° German "Sägegewinde" (saw tooth) buttress thread form4 |
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 thread78 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.
Wikipedia content modification information:
- This page was last modified on 26 December 2008, at 04:57.
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