Buttress thread

Buttress thread form refers to one of several screw thread profiles.

"Buttress thread" in machinery

In machinery, "buttress thread" is a thread form designed to handle extremely high axial thrust in one direction. (The resistance to axial thrust in the other direction is lower, being somewhat less than that of V-threads.) The load-bearing thread face is perpendicular to the screw axis. [cite book
last = Barnwell
first = George W.
title = The new encyclopedia of machine shop practice
publisher = Wm. H. Wise & Co.
date = 1941
pages = 163
] or at a slight slant (typically 7 degrees) [US patent reference | number=5127784 | y=1992 | m=07 | d=07 | inventor=David Eslinger | title=Fatigue-resistent buttress thread] The other face is slanted at about 45 degrees. The resulting thread form has the same low friction properties as square thread but at about twice the strength. In German it is called a "saw thread" "(Sägegewinde)" because the threadform resembles saw teeth.

One application in which the average person may see buttress threads is on a tube of toothpaste with a threaded cap. The threads to hold the cap on are sometimes made in buttress form, because this form best resists the force that tends toward blowing the cap off if the tube is squeezed at inadvertent times (such as while being packed inside a traveler's suitcase).

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.

"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 [US patent reference | number=6893057 | y=2005 | m=05 | d=17 | inventor=M. Edward Evans | title=Threaded pipe connection] [ [http://www.glossary.oilfield.slb.com/Display.cfm?Term=buttress%20thread Oil field glossary entry for "buttress thread"] ] the force is transmitted almost parallel to the axis and thread is about the same strength as standard v threads.

ee also

* Screw thread
* Acme thread form
* Square thread form


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