UNEF/UNREF - Extra Fine 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)
#12* (0.216)	0.2160	32	0.1957	0.1788	0.1822	0.0242	0.0270
1/4	0.2500	32	0.2297	0.2128	0.2162	0.0344	0.0379
5/16	0.3125	32	0.2922	0.2753	0.2787	0.0581	0.0625
3/8	0.3750	32	0.3547	0.3378	0.3412	0.0878	0.0932
7/16	0.4375	28	0.4143	0.3949	0.3988	0.1201	0.1274
1/2	0.5000	28	0.4768	0.4574	0.4613	0.1620	0.1700
9/16	0.5625	24	0.5354	0.5129	0.5174	0.2030	0.2140
5/8	0.6250	24	0.5979	0.5754	0.5799	0.2560	0.2680
11/16*	0.6875	24	0.6604	0.6379	0.6424	0.3150	0.3290
3/4	0.7500	20	0.7175	0.6905	0.6959	0.3690	0.3860
13/16*	0.8125	20	0.7800	0.7530	0.7584	0.4390	0.4580
7/8	0.8750	20	0.8425	0.8155	0.8209	0.5150	0.5360
15/16*	0.9375	20	0.9050	0.8780	0.8834	0.5980	0.6200
1	1.0000	20	0.9675	0.9405	0.9459	0.6870	0.7110
1 1/16*	1.0625	18	1.0264	0.9964	1.0024	0.7700	0.7990
1 1/8	1.1250	18	1.0889	1.0589	1.0649	0.8710	0.9010
1 3/16*	1.1875	18	1.1514	1.1214	1.1274	0.9770	1.0090
1 1/4	1.2500	18	1.2139	1.1839	1.1899	1.0900	1.1230
1 5/16*	1.3125	18	1.2764	1.2464	1.2524	1.2080	1.2440
1 3/8	1.3750	18	1.3389	1.3089	1.3149	1.3330	1.3700
1 7/16*	1.4375	18	1.4014	1.3714	1.3774	1.4640	1.5030
1 1/2	1.5000	18	1.4639	1.4339	1.4399	1.6000	1.6400
1 9/16*	1.5625	18	1.5264	1.4964	1.5024	1.7400	1.7900
1 5/8	1.6250	18	1.5889	1.5589	1.5649	1.8900	1.9400
1 11/16*	1.6875	18	1.6514	1.6214	1.6274	2.0500	2.1000
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.