Screw thread

threadedthreadthreadspitchthreads per inchscrew threadsthread pitchTPIthreadingbolt
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force.wikipedia
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Screw (simple machine)

screwscrewsendless screw
A screw thread is the essential feature of the screw as a simple machine and also as a fastener.
The most common form consists of a cylindrical shaft with helical grooves or ridges called threads around the outside.

Nut (hardware)

nutnutshex nut
A nut is a type of fastener with a threaded hole.

Worm drive

worm gearwormworm gears
A worm drive is a gear arrangement in which a worm (which is a gear in the form of a screw) meshes with a worm gear (which is similar in appearance to a spur gear).

Threaded pipe

threadedPipe threadpipe threads
The threaded pipes used in some plumbing installations for the delivery of fluids under pressure have a threaded section that is slightly conical.
A threaded pipe is a pipe with screw-threaded ends for assembly.

Jack (device)

jackhydraulic jackjacks
A mechanical jack employs a screw thread for lifting heavy equipment.


A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force.
Most hardware screw threads are right-handed helices.


For example, a screw has male threads, while its matching hole (whether in nut or substrate) has female threads.
The legal/statutory/regulatory wording uses the terms "coarse" and "fine" to refer to the tightness of the tolerance range, referring basically to "high-quality" or "low-quality", but this is a poor choice of terms, because those terms in the fastener industry have a different meaning (referring to the steepness of the helix's lead).

Edison screw

Edison basescrew baseE10 screw
The bulbs have right-hand threaded metal bases (caps) which screw into matching threaded sockets (lamp holders).


turnbucklesbottle screws
It normally consists of two threaded eye bolts, one screwed into each end of a small metal frame, one with a left-hand thread and the other with a right-hand thread.

Buttress thread

buttressBreech-Lock Thread Form
For buttress threads, the triangle is scalene.
The buttress thread form, also known as the breech-lock thread form, refers to two different thread profiles.

Unified Thread Standard

The common V-thread standards (ISO 261 and Unified Thread Standard) include a coarse pitch and a fine pitch for each major diameter.
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.

Tap and die

Thread limit or pitch diameter limit is a standard used for classifying the tolerance of the thread pitch diameter for taps.
Taps and dies are tools used to create screw threads, which is called threading.


lathesreducing lathelathing
The tool-post may be driven manually or automatically to produce the roughing and finishing cuts required to turn the workpiece to the desired shape and dimensions, or for cutting threads, worm gears, etc. Cutting fluid may also be pumped to the cutting site to provide cooling, lubrication and clearing of swarf from the workpiece.

National pipe thread

NPTFNPT2iron pipe
Examples are the NPT and BSP series.
American National Standard Pipe Thread standards, often called national pipe thread standards for short, are U.S. national technical standards for screw threads used on threaded pipes and pipe fittings.

Screw-cutting lathe

screw cutting lathelathe
In 1569 Besson invented the screw-cutting lathe, but the method did not gain traction and screws continued to be made largely by hand for another 150 years.
A screw-cutting lathe is a machine (specifically, a lathe) capable of cutting very accurate screw threads via single-point screw-cutting, which is the process of guiding the linear motion of the tool bit in a precisely known ratio to the rotating motion of the workpiece.

British Standard Pipe

British standard pipe threadBSPBritish standard
Examples are the NPT and BSP series.
British Standard Pipe (BSP) technical standards for screw threads that has been adopted internationally for interconnecting and sealing pipes and fittings by mating an external (male) thread with an internal (female) thread.

British Standard Whitworth

BSWWhitworthWhitworth thread
In 1841, Joseph Whitworth created a design that, through its adoption by many British railroad companies, became a national standard for the United Kingdom called British Standard Whitworth.
British Standard Whitworth (BSW) is an imperial-unit-based screw thread standard.

ISO metric screw thread

metricISO 261ISO 262
The common V-thread standards (ISO 261 and Unified Thread Standard) include a coarse pitch and a fine pitch for each major diameter.
The ISO metric screw threads are the most commonly used type of general-purpose screw thread worldwide.

Pipe dope

thread sealing compoundthread-sealing compound
Normally a good seal requires the application of a separate sealant into the joint, such as thread seal tape, or a liquid or paste pipe sealant such as pipe dope, however some threaded pipe joints do not require a separate sealant.
Pipe dope is any thread lubricant, thread sealing compound, and anaerobic chemical sealants that are used to make a pipe thread joint leak proof and pressure tight.

Bicycle pedal

pedalspedalclipless pedal
The pedal spindle is threaded to match a threaded hole at the outboard end of the cranks.

Spark plug

spark plugsplugsparkplug
A spark plug has a metal threaded shell, electrically isolated from a central electrode by a porcelain insulator.

British Association screw threads

BABA system (British Association)British Association (B.A.) screw threads
Over the next 30 years the standard was further defined and extended and evolved into a set of standards including National Coarse (NC), National Fine (NF), and National Pipe Taper (NPT). Meanwhile, in Britain, the British Association screw threads were also developed and refined.
British Association screw threads, or BA screw threads, are a largely obsolete set of small screw threads, the largest being 0BA at 6 mm diameter.


Standardization of screw threads has evolved since the early nineteenth century to facilitate compatibility between different manufacturers and users.
This allowed for the standardisation of screw thread sizes for the first time and paved the way for the practical application of interchangeability (an idea that was already taking hold) to nuts and bolts.