ASME B18.2.1 dimensions — Hex cap screws, inch series (Table 6 profile)

2012 edition, current · 28 sizes, 1/4-20 UNC – 1-1/2-12 UNF see the cross-reference →

We supply to ASME B18.2.1. Name it on your order.

ASME B18.2.1 dimensions

Thread size	dBasic Major Diameter (in)	TPIThreads Per Inch	Thread Series	Thread Class	d maxBody Diameter Max (in)	d minBody Diameter Min (in)	sWidth Across Flats (max) (in)	sWidth Across Flats (min) (in)	eWidth Across Corners (min) (in)	eWidth Across Corners (max) (in)	kNominal Head Height (in)	kHead Height (min) (in)	JWrenching Height (min) (in)	LTNominal Thread Length (L≤6 in) (in)	LTNominal Thread Length (L>6 in) (in)
1/4-20 UNC	0.25	20	UNC	2A	0.25	0.245	0.438	0.428	0.488	0.505	0.163	0.15	0.106	0.75	1
1/4-28 UNF	0.25	28	UNF	2A	0.25	0.245	0.438	0.428	0.488	0.505	0.163	0.15	0.106	0.75	1
5/16-18 UNC	0.3125	18	UNC	2A	0.3125	0.3065	0.5	0.489	0.557	0.577	0.211	0.195	0.14	0.875	1.125
5/16-24 UNF	0.3125	24	UNF	2A	0.3125	0.3065	0.5	0.489	0.557	0.577	0.211	0.195	0.14	0.875	1.125
3/8-16 UNC	0.375	16	UNC	2A	0.375	0.369	0.562	0.551	0.628	0.65	0.243	0.226	0.16	1	1.25
3/8-24 UNF	0.375	24	UNF	2A	0.375	0.369	0.562	0.551	0.628	0.65	0.243	0.226	0.16	1	1.25
7/16-14 UNC	0.4375	14	UNC	2A	0.4375	0.4305	0.625	0.612	0.698	0.722	0.291	0.272	0.195	1.125	1.375
7/16-20 UNF	0.4375	20	UNF	2A	0.4375	0.4305	0.625	0.612	0.698	0.722	0.291	0.272	0.195	1.125	1.375
1/2-13 UNC	0.5	13	UNC	2A	0.5	0.493	0.75	0.736	0.84	0.866	0.323	0.302	0.215	1.25	1.5
1/2-20 UNF	0.5	20	UNF	2A	0.5	0.493	0.75	0.736	0.84	0.866	0.323	0.302	0.215	1.25	1.5
9/16-12 UNC	0.5625	12	UNC	2A	0.5625	0.5545	0.812	0.798	0.91	0.938	0.371	0.348	0.25	1.375	1.625
9/16-18 UNF	0.5625	18	UNF	2A	0.5625	0.5545	0.812	0.798	0.91	0.938	0.371	0.348	0.25	1.375	1.625
5/8-11 UNC	0.625	11	UNC	2A	0.625	0.617	0.938	0.922	1.051	1.083	0.403	0.378	0.269	1.5	1.75
5/8-18 UNF	0.625	18	UNF	2A	0.625	0.617	0.938	0.922	1.051	1.083	0.403	0.378	0.269	1.5	1.75
3/4-10 UNC	0.75	10	UNC	2A	0.75	0.741	1.125	1.1	1.254	1.299	0.483	0.455	0.324	1.75	2
3/4-16 UNF	0.75	16	UNF	2A	0.75	0.741	1.125	1.1	1.254	1.299	0.483	0.455	0.324	1.75	2
7/8-9 UNC	0.875	9	UNC	2A	0.875	0.866	1.312	1.285	1.465	1.516	0.563	0.531	0.378	2	2.25
7/8-14 UNF	0.875	14	UNF	2A	0.875	0.866	1.312	1.285	1.465	1.516	0.563	0.531	0.378	2	2.25
1-8 UNC	1	8	UNC	2A	1	0.99	1.5	1.469	1.675	1.732	0.627	0.591	0.416	2.25	2.5
1-12 UNF	1	12	UNF	2A	1	0.99	1.5	1.469	1.675	1.732	0.627	0.591	0.416	2.25	2.5
1-1/8-7 UNC	1.125	7	UNC	2A	1.125	1.114	1.688	1.631	1.859	1.949	0.718	0.658	0.461	2.5	2.75
1-1/8-12 UNF	1.125	12	UNF	2A	1.125	1.114	1.688	1.631	1.859	1.949	0.718	0.658	0.461	2.5	2.75
1-1/4-7 UNC	1.25	7	UNC	2A	1.25	1.239	1.875	1.812	2.066	2.165	0.813	0.749	0.53	2.75	3
1-1/4-12 UNF	1.25	12	UNF	2A	1.25	1.239	1.875	1.812	2.066	2.165	0.813	0.749	0.53	2.75	3
1-3/8-6 UNC	1.375	6	UNC	2A	1.375	1.363	2.062	1.994	2.273	2.382	0.878	0.81	0.569	3	3.25
1-3/8-12 UNF	1.375	12	UNF	2A	1.375	1.363	2.062	1.994	2.273	2.382	0.878	0.81	0.569	3	3.25
1-1/2-6 UNC	1.5	6	UNC	2A	1.5	1.488	2.25	2.175	2.48	2.598	0.974	0.902	0.64	3.25	3.5
1-1/2-12 UNF	1.5	12	UNF	2A	1.5	1.488	2.25	2.175	2.48	2.598	0.974	0.902	0.64	3.25	3.5

28 of 28 sizes shown.

ASME B18.2.1 sizes

9 diameters · weight and hole sizes live on each size page

1/4-20 UNC 5/16-18 UNC 3/8-16 UNC 7/16-14 UNC 1/2-13 UNC 5/8-11 UNC 3/4-10 UNC 7/8-9 UNC 1-8 UNC All 147 sizes in this family →

What we supply to ASME B18.2.1

1 materials

Material	Property class	Finish
Carbon Steel	Grade 5 · Grade 8 · Grade A	Zinc Plated · Blackened · Plain · Hot Dip Galvanized

Equivalents and mating parts

ASME B1.1-2024 →ASTM A307 →ASTM F593 →Hex cap screws — inch series (Table 6 profile) sizes and weights →

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