Sandvik Coromant Threading - Manual (Page 3)

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1. Basic in threads
1. Basics in threads
What is a thread?
Threads are classifi ed according to the main functions they perform in a component.
Primary functions of a thread:
• To form a mechanical coupling
• To transmit motion by converting a rotational movement into a linear movement, and vice
versa.
• To obtain a mechanical advantage, by using a small force to
create a larger force.
Threads are also classifi ed into various profi les or forms. The selection of these forms will
be infl uenced by many other secondary, but still vital, functions.
Thread forms
The thread profi le defi nes the geometry of a thread and includes component diameters
(major, pitch and minor), the thread profi le angle, pitch and helix angle. The most common
thread forms or profi les produced today are shown below.
Application Thread form Thread type
Connecting
General usage
ISO metric, American UN
Pipe threads Whitworth, British Standard (BSPT),
American National, Pipe Threads,
NPT, NPTF
Food and fi re Round DIN 405
Aerospace MJ, UNJ
Oil and gas API Rounded, API Buttress, VAM
Motion
General usage
Trapezoidal, ACME, Stub ACME