Buttress thread
Encyclopedia
The buttress thread form, also known as the breech-lock 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.
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
.
Buttress threads have often been used in the construction of artillery
, particularly with the screw-type breechblock
. They are also often used in vises, because great force is only required in one direction.
the force is transmitted almost parallel to the axis and thread is about the same strength as standard v threads.
Screw thread
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread...
profiles. One is a type of leadscrew
Leadscrew
A leadscrew , also known as a power screw or translation screw, is a screw designed to translate turning motion into linear motion...
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
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. or at a slight slant (usually no greater than 7°) The other face is slanted at 45°. The resulting thread form has the same low friction properties as a square thread formSquare thread form
The square thread form is a common thread form for leadscrews. It gets its name from the square cross-section of the thread.-Advantages & disadvantages:...
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
Split nut
A split nut is a nut that consists of two pieces which can be clamped together to engage the thread of the nut with the bolt, or released, to allow the nut to move along the bolt without turning the bolt. The two pieces have chamfered ends . The nut is split lengthwise so that it may be opened for...
, much like the Acme thread form
Acme thread form
Trapezoidal thread forms are screw thread profiles with trapezoidal outlines. They are the most common forms used for leadscrews . They offer high strength and ease of manufacture. They are typically found where large loads or high accuracy are required, as in a vise or the leadscrew of a lathe...
.
Buttress threads have often been used in the construction of artillery
Artillery
Originally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...
, particularly with the screw-type breechblock
Breechblock
A breechblock is the part of the firearm action that closes the breech of a weapon at the moment of firing....
. They are also often used in vises, because great force is only required in one direction.
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 threadthe force is transmitted almost parallel to the axis and thread is about the same strength as standard v threads.