United States Standard thread (USS thread), also known as Sellers Standard thread,
Franklin Institute thread
and American Standard thread, is a standard for inch based threaded
fasteners and
washer
Washer most commonly refers to:
*Washer (hardware), a thin usually disc-shaped plate with a hole in the middle typically used with a bolt or nut
*Washing machine, for cleaning clothes
Washer may also refer to:
*Dishwasher, a machine for cleani ...
s.
The USS standard is no longer supported. It, together with the
SAE
SAE or Sae may refer to:
Science and technology
:
* Selective area epitaxy, local growth of epitaxial layer through a patterned dielectric mask deposited on a semiconductor substrate
* Serious adverse event, in a clinical trial
* Simultaneous Auth ...
fastener standard, was incorporated into the
Unified Thread Standard. However, the term, ''USS'', continues to be used occasionally today to describe inch based threaded fasteners with a coarse thread pitch and inch based washers that are a little bit larger than the corresponding SAE washer. The Unified Thread Standard uses the term UNC (Unified Coarse) to describe a fastener that previously would have been designated USS and the Unified Thread Standard uses the term UNF (Unified Fine) to describe a fastener that would have previously been designated SAE.
Thread form
The thread form is defined by flats at the tip and root of the thread form. This flat length is defined as the pitch divided by eight. The thread depth, which is from flat to flat is 0.6495 times the pitch. For screws and larger, the pitch is defined as:
:
where ''P'' is the pitch and ''D'' is the diameter of the rough stock.
History and use
William Sellers originally developed the USS thread, and set forth many of its details in his paper, "A System of Screw Threads and Nuts", presented in April 1864 to the
Franklin Institute. In 1898, the standard for metric threaded fasteners was established. The metric standard used the same thread geometry as the USS standard but differed in that the dimensions and pitch were based on metric units. In 1906, the
A.L.A.M developed what would be the
SAE
SAE or Sae may refer to:
Science and technology
:
* Selective area epitaxy, local growth of epitaxial layer through a patterned dielectric mask deposited on a semiconductor substrate
* Serious adverse event, in a clinical trial
* Simultaneous Auth ...
thread standard for threaded fasteners based on the USS standard but with a finer thread pitch.
A Unified Thread Standard UNC thread is mechanically interchangeable with a USS thread of the same diameter. However, there are tolerance and other differences between a thread compliant with the USS thread and a Unified Thread Standard UNC thread. The Unified Thread Standard for quarter inch and larger threaded fasteners was adopted on November 18, 1948,
and was subsequently adopted for smaller thread series.
See also
*
British Standard Whitworth
British Standard Whitworth (BSW) is an imperial-unit-based screw thread standard, devised and specified by Joseph Whitworth in 1841 and later adopted as a British Standard. It was the world's first national screw thread standard, and is the basis ...
*
"History of standardization" section of the screw thread article
*
ISO metric screw thread
*
Screw
*
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 ...
*
Unified Thread Standard
References
{{reflist
External links
The United States Standard Screw Threads (1864)Text of Seller's presentation to the Franklin Institute, April 21, 1864
Screws
Thread standards
Standards of the United States