The thread angle of a screw is the included angle between the thread flanks, measured in a plane containing the thread axis.This is a defining factor for the shape of a screw thread. Standard values include:
(including ISO, NPT and UTS)
|M||60°||DIN 13 / ISO ? / ASME/ANSI ?|
|Whitworth threads||W||55°||DIN 49301 / BS ?|
|G||55°||DIN / BS / EN / ISO 228-1 / ISO 7-1|
|Pipe thread |
National Pipe Thread
|NPT||60||see wikipedia page on |
NPT threads as I can't upload a
profile drawing from another
|ASME B1.20.-1983 Pipe Threads, General Purpose, Inch|
|Rd||30°||DIN 405 / DIN 20400|
|Acme thread||29°||ASME/ANSI B1.5-1988|
|Metric trapezoidal threads||Tr||30°||DIN 103|
|Buttress threads||S||45°||DIN 2781|
|German buttress threads||S||30°||DIN 513|
|British Association (BA) thread||BA||?||BS 93:2008|
The Unified Thread Standard (UTS) defines a standard thread form and series—along with allowances, tolerances, and designations—for screw threads commonly used in the United States and Canada. It is the main standard for bolts, nuts, and a wide variety of other threaded fasteners used in these countries. It has the same 60° profile as the ISO metric screw thread, but the characteristic dimensions of each UTS thread were chosen as an inch fraction rather than a millimeter value. The UTS is currently controlled by ASME/ANSI in the United States.
American National Standard Pipe Thread standards, often called national pipe thread (NPT) standards for short, are U.S. national technical standards for screw threads used on threaded pipes and pipe fittings. They include both tapered and straight thread series for various purposes including rigidity, pressure-tight sealing, or both. The various types are each named with a symbol and a full name; examples of the symbols include NPT, NPS, NPTF, NPSC, and others.
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. A screw thread is the essential feature of the screw as a simple machine and also as a threaded fastener.
A thread gauge, also known as a screw gauge or pitch gauge, is used to measure the pitch or lead of a screw thread.
British Standard Whitworth (BSW) is an imperial-unit-based screw thread standard.
A leadscrew, also known as a power screw or translation screw, is a screw used as a linkage in a machine, to translate turning motion into linear motion. Because of the large area of sliding contact between their male and female members, screw threads have larger frictional energy losses compared to other linkages. They are not typically used to carry high power, but more for intermittent use in low power actuator and positioner mechanisms. Leadscrews are commonly used in linear actuators, machine slides, vises, presses, and jacks. Leadscrews are a common component in electric linear actuators.
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 are required, as in a vise or the leadscrew of a lathe. Standardized variations include multiple-start threads, left-hand threads, and self-centering threads.
A screw is a mechanism that converts rotational motion to linear motion, and a torque to a linear force. It is one of the six classical simple machines. The most common form consists of a cylindrical shaft with helical grooves or ridges called threads around the outside. The screw passes through a hole in another object or medium, with threads on the inside of the hole that mesh with the screw's threads. When the shaft of the screw is rotated relative to the stationary threads, the screw moves along its axis relative to the medium surrounding it; for example rotating a wood screw forces it into wood. In screw mechanisms, either the screw shaft can rotate through a threaded hole in a stationary object, or a threaded collar such as a nut can rotate around a stationary screw shaft. Geometrically, a screw can be viewed as a narrow inclined plane wrapped around a cylinder.
The ISO metric screw threads are the most commonly used type of general-purpose screw thread worldwide. They were one of the first international standards agreed when the International Organization for Standardization (ISO) was set up in 1947.
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. The asymmetric thread form allows the thread to have low friction and withstand greater loads than other forms in one direction, but at the cost of higher friction and inferior load bearing in the opposite direction.
In mechanical engineering, a helix angle is the angle between any helix and an axial line on its right, circular cylinder or cone. Common applications are screws, helical gears, and worm gears.
A screw and a bolt are similar types of fastener typically made of metal, and characterized by a helical ridge, known as a male thread. Screws and bolts are used to fasten materials by the engagement of the screw thread with a similar female thread in the matching part.
The square thread form is a common screw thread form, used in high load applications such as leadscrews and jackscrews. It gets its name from the square cross-section of the thread. It is the lowest friction and most efficient thread form, but it is difficult to fabricate.
Threading is the process of creating a screw thread. More screw threads are produced each year than any other machine element. There are many methods of generating threads, including subtractive methods ; deformative or transformative methods ; additive methods ; or combinations thereof.
United States Standard thread, also known as Sellers Standard thread, Franklin Institute thread and American Standard thread, is a standard for inch based threaded fasteners and washers.
A threaded rod, also known as a stud, is a relatively long rod that is threaded on both ends; the thread may extend along the complete length of the rod. They are designed to be used in tension. Threaded rod in bar stock form is often called all-thread.
Machine element refers to an elementary component of a machine. These elements consist of three basic types:
A mechanical joint is a section of a machine which is used to connect one or more mechanical part to another. Mechanical joints may be temporary or permanent, most types are designed to be disassembled. Most mechanical joints are designed to allow relative movement of these mechanical parts of the machine in one degree of freedom, and restrict movement in one or more others.
Knuckle threads are an unusual highly rounded thread form. The large space between the rounded crests and roots provides space for debris to be shifted to not interfere with the thread, making this form resistant to debris and thread damage.
The Löwenherz thread is a largely obsolete metric thread form designed in the late nineteenth century and frequently applied in precision instruments. It is named after Dr. Leopold Löwenherz, who was the director of the metrology institute Physikalisch-Technische Bundesanstalt in Berlin.