UNC/UNRC - Coarse Thread (in)

Bolt Size	Major Diameter (in)	Threads per Inch (tpi)	Pitch Diameter (in)	Minor Diameter External (in) a)	Minor Diameter Internal (in) b)	Minor Diameter Area (sq in)	Tensile Stress Area (sq in)
#1*	0.073	64	0.0629	0.0544	0.0561	0.00218	0.00263
#2	0.086	56	0.0744	0.0648	0.0667	0.0031	0.0037
#3*	0.099	48	0.0855	0.0741	0.0764	0.00406	0.00487
#4	0.112	40	0.0958	0.0822	0.0849	0.00496	0.00604
#5	0.125	40	0.1088	0.0952	0.0979	0.00672	0.00796
#6	0.138	32	0.1177	0.1008	0.1042	0.00745	0.00909
#8	0.164	32	0.1437	0.1268	0.1302	0.01196	0.014
#10	0.19	24	0.1629	0.1404	0.1449	0.0145	0.0175
#12*	0.216	24	0.1889	0.1664	0.1709	0.0206	0.0242
1/4	0.25	20	0.2175	0.1905	0.1959	0.0269	0.0318
5/16	0.3125	18	0.2764	0.2464	0.2524	0.0454	0.0524
3/8	0.375	16	0.3344	0.3005	0.3073	0.0678	0.0775
7/16	0.4375	14	0.3911	0.3525	0.3602	0.0933	0.1063
1/2	0.5	13	0.45	0.4084	0.4167	0.1257	0.1419
9/16	0.5625	12	0.5084	0.4633	0.4723	0.162	0.182
5/8	0.625	11	0.566	0.5168	0.5266	0.202	0.226
3/4	0.75	10	0.685	0.6309	0.6417	0.302	0.334
7/8	0.875	9	0.8028	0.7427	0.7547	0.419	0.462
1	1	8	0.9188	0.8512	0.8647	0.551	0.606
1 1/8	1.125	7	1.0322	0.9549	0.9704	0.693	0.763
1 1/4	1.25	7	1.1572	1.0799	1.0954	0.89	0.969
1 3/8	1.375	6	1.2667	1.1766	1.1946	1.054	1.155
1 1/2	1.5	6	1.3917	1.3016	1.3196	1.294	1.405
1 3/4	1.75	5	1.6201	1.5119	1.5335	1.74	1.9
2	2	4.5	1.8557	1.7353	1.7594	2.3	2.5
2 1/4	2.25	4.5	2.1057	1.9853	2.0094	3.02	3.25
2 1/2	2.5	4	2.3376	2.2023	2.2294	3.72	4
2 3/4	2.75	4	2.5876	2.4523	2.4794	4.62	4.93
3	3	4	2.8376	2.7023	2.7294	5.62	5.97
3 1/4	3.25	4	3.0876	2.9523	2.9794	6.72	7.1
3 1/2	3.5	4	3.3376	3.2023	3.2294	7.92	8.33
3 3/4	3.75	4	3.5876	3.4523	3.4794	9.21	9.66
4	4	4	3.8376	3.7023	3.7294	10.61	11.08
Bolt Size	Major Diameter (in)	Threads per Inch (tpi)	Pitch Diameter (in)	Minor Diameter External (in) a)	Minor Diameter Internal (in) b)	Minor Diameter Area (sq in)	Tensile Stress Area (sq in)
* Secondary Size		a) Form for UNR thread			b) Basic Minor Diameter

Notes:

• a) For Class 2A threads with coating (plating) the max. is increased by the allowance, to the basic size. This is the same value as Class 3A.
• b) For uncoated hot-rolled, but not standard fasteners with cold rolled threads.
• c) UN series external thread, Max. Diameter, allows for Class 1A and 2A and basic for Class 3A.