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Inch series · technical reference

Threaded Rod Dimensions

A naming and thread-series reference for continuous-thread rod. Unlike a headed bolt, a threaded rod has no under-head length definition: the ordered overall length and end condition must be stated separately.

Source: ASME B18.31.2.

StandardASME B18.31.2 · Inch Series
RevisionSource review · 2026-09
Unitsinches
CAD ORTHOGRAPHIC REFERENCEASME B18.31.2 · INCH SERIES REFERENCE
ASME B18.31.2 continuous thread UNC threaded rod dimension drawing, side view with dimension callouts, 1/4-20 UNC reference size
SIDE VIEW · LENGTH REFERENCE · 1/4-20 UNC
ASME B18.31.2 continuous thread UNC threaded rod dimension drawing, end view, 1/4-20 UNC reference size
END VIEW · THREAD · 1/4-20 UNC

Reference size shown: 1/4-20 UNC. The drawing identifies dimension locations only. Use the table for nominal data and confirm the exact product configuration before ordering.

Common continuous-thread UNC designations
Thread designationd — nominal ØTPIThread seriesThread coverage
1/4-200.25020UNCContinuous
5/16-180.31318UNCContinuous
3/8-160.37516UNCContinuous
1/2-130.50013UNCContinuous
5/8-110.62511UNCContinuous
3/4-100.75010UNCContinuous

Illustration is not to scale. Specify the complete thread designation, overall length, material, finish and end requirement when requesting a rod or stud.