Buttress thread

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Buttress thread form

The buttress thread form, also known as the breech-lock thread form,[1] 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.

Buttress thread in machinery[edit]

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.[2] or at a slight slant (usually no greater than 7°)[3] 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 the shear 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.[4]

Buttress threads have often been used in the construction of artillery, particularly with the screw-type breechblock.[1] They are also often used in vises, because great force is only required in one direction.[4]

Types[edit]

The image gallery below shows some of the types of buttress threads.

Mechanics[edit]

Main article: Leadscrew

Buttress thread in oil field tubing[edit]

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[8][9] the force is transmitted almost parallel to the axis and thread is about the same strength as standard v threads.

References[edit]

  1. ^ a b http://books.google.com/books?id=gYZIAAAAMAAJ&pg=PA141
  2. ^ Barnwell, p. 163.
  3. ^ US patent 5127784, David Eslinger, "Fatigue-resistant buttress thread", issued 1992-07-07 
  4. ^ a b Bhandari, p. 204.
  5. ^ a b c Oberg, p.1817
  6. ^ Oberg, pp. 1819–1820.
  7. ^ Timings, p. 127.
  8. ^ US patent 6893057, M. Edward Evans, "Threaded pipe connection", issued 2005-05-17  Figure 6.
  9. ^ Oil field glossary entry for buttress thread

Bibliography[edit]