Inch series · technical reference

Hex Flange Bolt Dimensions

Head and integral-flange geometry for the heavy-series inch hex flange bolt. A separate washer is not represented by the integral flange, and small-series or metric flange bolts require their own standard.

Source: ASME B18.2.1.

StandardASME B18.2.1.8 · Inch Series

RevisionSource review · 2026-09

Unitsinches

CAD ORTHOGRAPHIC REFERENCEASME B18.2.1.8 · INCH SERIES REFERENCE

ASME B18.2.1 hex flange bolt dimension drawing, side view with dimension callouts, 1/4-20 UNC reference size — SIDE VIEW · LENGTH REFERENCE · 1/4-20 UNC

ASME B18.2.1 hex flange bolt dimension drawing, end view, 1/4-20 UNC reference size — END VIEW · HEAD / DRIVE · 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.

Heavy-series flange-head geometry
Nominal size	TPI	dc — flange Ø	kw — wrenching height max	s — WAF
1/4 in	20	0.563	0.17	0.375
5/16 in	18	0.688	0.21	0.500
3/8 in	16	0.813	0.25	0.563
7/16 in	14	0.938	0.30	0.625
1/2 in	13	1.078	0.34	0.750
5/8 in	11	1.328	0.42	0.938
3/4 in	10	1.594	0.51	1.125