Unified Screw Threads, Standard Series

Nominal Thread Size	Covered Range
0-80 UNF to ¼-56 UNS	Nominal thread sizes from 0-80 UNF to ¼-56 UNS
5/16-18 UNC to 9/16 -32 UN	Nominal thread sizes from 5/16-18 UNC to 9/16 -32 UN
5/8-11 UNC to 7/8-32 UN	Nominal thread sizes from 5/8-11 UNC to 7/8-32 UN
15/16-12 UN to 1 3/16-28 UN	Nominal thread sizes from 15/16-12 UN to 1 3/16-28 UN
1 1/4-7 UNC to 1 9/16-20 UN	Nominal thread sizes from 1 1/4-7 UNC to 1 9/16-20 UN
1 5/8-6 UN to 1 15/16-20 UN	Nominal thread sizes from 1 5/8-6 UN to 1 15/16-20 UN
2-4½ UNC to 2¾-20 UN	Nominal thread sizes from 2-4½ UNC to 2¾-20 UN
2 7/8-6 UN to 4-16 UN	Nominal thread sizes from 2 7/8-6 UN to 4-16 UN

External Thread /Internal Thread
	Nominal Size, TPI, Series	Class	Allowance	Max^a Major Max Minor	Min Major Min Minor	Min ^b	Max^a Pitch	Min Pitch	UNR^c Minor Dia Major Dia(Min)
Ext.	¹⁵/₁₆-12 UN	2A	0.0017	0.9358	0.9244	-	0.8817	0.8760	0.8366
Int.		2B		0.8650	0.8470		0.8908	0.8834	0.9375
Ext.	¹⁵/₁₆-12 UN	3A	0.0000	0.9375	0.9261	-	0.8834	0.8793	0.8383
Int.		3B		0.8575	0.8470		0.8889	0.8834	0.9375
Ext.	¹⁵/₁₆-16 UN	2A	0.0015	0.9360	0.9266	-	0.8954	0.8904	0.8615
Int.		2B		0.8840	0.8700		0.9034	0.8969	0.9375
Ext.	¹⁵/₁₆-16 UN	3A	0.0000	0.9375	0.9281	-	0.8969	0.8932	0.8630
Int.		3B		0.8783	0.8700		0.9018	0.8969	0.9375
Ext.	¹⁵/₁₆-20 UNEF	2A	0.0014	0.9361	0.9280	-	0.9036	0.8991	0.8766
Int.		2B		0.8950	0.8830		0.9109	0.9050	0.9375
Ext.	¹⁵/₁₆-20 UNEF	3A	0.0000	0.9375	0.9294	-	0.9050	0.9016	0.8780
Int.		3B		0.8912	0.8830		0.9094	0.9050	0.9375
Ext.	¹⁵/₁₆-28 UN	2A	0.0012	0.9363	0.9298	-	0.9131	0.9091	0.8937
Int.		2B		0.9070	0.8990		0.9195	0.9143	0.9375
Ext.	¹⁵/₁₆-28 UN	3A	0.0000	0.9375	0.9310	-	0.9143	0.9113	0.8949
Int.		3B		0.9051	0.8990		0.9182	0.9143	0.9375
Ext.	¹⁵/₁₆-32 UN	2A	0.0011	0.9364	0.9304	-	0.9161	0.9123	0.8992
Int.		2B		0.9110	0.9040		0.9221	0.9172	0.9375
Ext.	¹⁵/₁₆-32 UN	3A	0.0000	0.9375	0.9315	-	0.9172	0.9144	0.9003
Int.		3B		0.9094	0.9040		0.9209	0.9172	0.9375
Ext.	1-8 UNC	1A	0.0020	0.9980	0.9755	-	0.9168	0.9067	0.8492
Int.		1B		0.8900	0.8650		0.9320	0.9188	1.0000
Ext.	1-8 UNC	2A	0.0020	0.9980	0.9830	0.9755	0.9168	0.9100	0.8492
Int.		2B		0.8900	0.8650		0.9276	0.9188	1.0000
Ext.	1-8 UNC	3A	0.0000	1.0000	0.9850	-	0.9188	0.9137	0.8512
Int.		3B		0.8797	0.8650		0.9254	0.9188	1.0000
Ext.	1-10 UNS	2A	0.0018	0.9982	0.9853	-	0.9332	0.9270	0.8792
Int.		2B		0.9130	0.8920		0.9430	0.9350	1.0000
Ext.	1-12 UNF	1A	0.0018	0.9982	0.9810	-	0.9441	0.9353	0.8990
Int.		1B		0.9280	0.9100		0.9573	0.9459	1.0000
Ext.	1-12 UNF	2A	0.0018	0.9982	0.9868	-	0.9441	0.9382	0.8990
Int.		2B		0.9280	0.9100		0.9535	0.9459	1.0000
Ext.	1-12 UNF	3A	0.0000	1.0000	0.9886	-	0.9459	0.9415	0.9008
Int.		3B		0.9198	0.9100		0.9516	0.9459	1.0000
Ext.	1-14UNS	1A	0.0017	0.9983	0.9828	-	0.9519	0.9435	0.9132
Int.		1B		0.9380	0.9230		0.9645	0.9536	1.0000
Ext.	1-14UNS	2A	0.0017	0.9983	0.9880	-	0.9519	0.9463	0.9132
Int.		2B		0.9380	0.9230		0.9609	0.9536	1.0000
Ext.	1-14UNS	3A	0.0000	1.0000	0.9897	-	0.9536	0.9494	0.9149
Int.		3B		0.9315	0.9230		0.9590	0.9536	1.0000
Ext.	1-16 UN	2A	0.0015	0.9985	0.9891	-	0.9579	0.9529	0.9240
Int.		2B		0.9460	0.9320		0.9659	0.9594	1.0000
Ext.	1-16 UN	3A	0.0000	1.0000	0.9906	-	0.9594	0.9557	0.9255
Int.		3B		0.9408	0.9320		0.9643	0.9594	1.0000
Ext.	1-18 UNS	2A	0.0014	0.9986	0.9899	-	0.9625	0.9578	0.9325
Int.		2B		0.9530	0.9400		0.9701	0.9639	1.0000
Ext.	1-20 UNEF	2A	0.0014	0.9986	0.9905	-	0.9661	0.9616	0.9391
Int.		2B		0.9570	0.9460		0.9734	0.9675	1.0000
Ext.	1-20 UNEF	3A	0.0000	1.0000	0.9919	-	0.9675	0.9641	0.9405
Int.		3B		0.9537	0.9460		0.9719	0.9675	1.0000
Ext.	1-24 UNS	2A	0.0013	0.9987	0.9915	-	0.9716	0.9674	0.9491
Int.		2B		0.9650	0.9550		0.9784	0.9729	1.0000
Ext.	1-27 UNS	2A	0.0012	0.9988	0.9921	-	0.9747	0.9707	0.9547
Int.		2B		0.9690	0.9600		0.9811	0.9759	1.0000
Ext.	1-28 UN	2A	0.0012	0.9988	0.9923	-	0.9756	0.9716	0.9562
Int.		2B		0.9700	0.9610		0.9820	0.9768	1.0000
Ext.	1-28 UN	3A	0.0000	1.0000	0.9935	-	0.9768	0.9738	0.9574
Int.		3B		0.9676	0.9610		0.9807	0.9768	1.0000
Ext.	1-32 UN	2A	0.0011	0.9989	0.9929	-	0.9786	0.9748	0.9617
Int.		2B		0.9740	0.9660		0.9846	0.9797	1.0000
Ext.	1-32 UN	3A	0.0000	1.0000	0.9940	-	0.9797	0.9769	0.9628
Int.		3B		0.9719	0.9660		0.9834	0.9797	1.0000
Ext.	1¹/₁₆-8 UN	2A	0.0020	1.0605	1.0455	-	0.9793	0.9725	0.9117
Int.		2B		0.9520	0.9270		0.9902	0.9813	1.0625
Ext.	1¹/₁₆-8 UN	3A	0.0000	1.0625	1.0475	-	0.9813	0.9762	0.9137
Int.		3B		0.9422	0.9270		0.9880	0.9813	1.0625
Ext.	1¹/₁₆-12 UN	2A	0.0017	1.0608	1.0494	-	1.0067	1.0010	0.9616
Int.		2B		0.9900	0.9720		1.0158	1.0084	1.0625
Ext.	1¹/₁₆-12 UN	3A	0.0000	1.0625	1.0511	-	1.0084	1.0042	0.9633
Int.		3B		0.9823	0.9720		1.0139	1.0084	1.0625
Ext.	1¹/₁₆-16 UN	2A	0.0015	1.0610	1.0516	-	1.0204	1.0154	0.9865
Int.		2B		1.0090	0.9950		1.0284	1.0219	1.0625
Ext.	1¹/₁₆-16 UN	3A	0.0000	1.0625	1.0531	-	1.0219	1.0182	0.9880
Int.		3B		1.0033	0.9950		1.0268	1.0219	1.0625
Ext.	1¹/₁₆-18 UNEF	2A	0.0014	1.0611	1.0524	-	1.0250	1.0203	0.9950
Int.		2B		1.0150	1.0020		1.0326	1.0264	1.0625
Ext.	1¹/₁₆-18 UNEF	3A	0.0000	1.0625	1.0538	-	1.0264	1.0228	0.9964
Int.		3B		1.0105	1.0020		1.0310	1.0264	1.0625
Ext.	1¹/₁₆-20 UN	2A	0.0014	1.0611	1.0530	-	1.0286	1.0241	1.0016
Int.		2B		1.0200	1.0080		1.0359	1.0300	1.0625
Ext.	1¹/₁₆-20 UN	3A	0.0000	1.0625	1.0544	-	1.0300	1.0266	1.0030
Int.		3B		1.0162	1.0080		1.0344	1.0300	1.0625
Ext.	1¹/₁₆-28 UN	2A	0.0012	1.0613	1.0548	-	1.0381	1.0341	1.0187
Int.		2B		1.0320	1.0240		1.0445	1.0393	1.0625
Ext.	1¹/₁₆-28 UN	3A	0.0000	1.0625	1.0560	-	1.0393	1.0363	1.0199
Int.		3B		1.0301	1.0240		1.0432	1.0393	1.0625
Ext.	1¹/₈-7 UNC	1A	0.0022	1.1228	1.0982	-	1.0300	1.0191	0.9527
Int.		1B		0.9980	0.9700		1.0463	1.0322	1.1250
Ext.	1¹/₈-7 UNC	2A	0.0022	1.1228	1.1064	1.0982	1.0300	1.0228	0.9527
Int.		2B		0.9980	0.9700		1.0416	1.0322	1.1250
Ext.	1¹/₈-7 UNC	3A	0.0000	1.1250	1.1086	-	1.0322	1.0268	0.9549
Int.		3B		0.9875	0.9700		1.0393	1.0322	1.1250
Ext.	1¹/₈-8 UN	2A	0.0021	1.1229	1.1079	1.1004	1.0417	1.0348	0.9741
Int.		2B		1.0150	0.9900		1.0528	1.0438	1.1250
Ext.	1¹/₈-8 UN	3A	0.0000	1.1250	1.1100	-	1.0438	1.0386	0.9762
Int.		3B		1.0047	0.9900		1.0505	1.0438	1.1250
Ext.	1¹/₈-10 UNS	2A	0.0018	1.1232	1.1103	-	1.0582	1.0520	1.0042
Int.		2B		1.0380	1.0170		1.0680	1.0600	1.1250
Ext.	1¹/₈-12 UNF	1A	0.0018	1.1232	1.1060	-	1.0691	1.0601	1.0240
Int.		1B		1.0530	1.0350		1.0826	1.0709	1.1250
Ext.	1¹/₈-12 UNF	2A	0.0018	1.1232	1.1118	-	1.0691	1.0631	1.0240
Int.		2B		1.0530	1.0350		1.0787	1.0709	1.1250
Ext.	1¹/₈-12 UNF	3A	0.0000	1.1250	1.1136	-	1.0709	1.0664	1.0258
Int.		3B		1.0448	1.0350		1.0768	1.0709	1.1250
Ext.	1¹/₈-14 UNS	2A	0.0016	1.1234	1.1131	-	1.0770	1.0717	1.0384
Int.		2B		1.0640	1.0480		1.0855	1.0786	1.1250
Ext.	1¹/₈-16 UN	2A	0.0015	1.1235	1.1141	-	1.0829	1.0779	1.0490
Int.		2B		1.0710	1.0570		1.0909	1.0844	1.1250
Ext.	1¹/₈-16 UN	3A	0.0000	1.1250	1.1156	-	1.0844	1.0807	1.0505
Int.		2B		1.0658	1.0570		1.0893	1.0844	1.1250
Ext.	1¹/₈-18 UNEF	2A	0.0014	1.1236	1.1149	-	1.0875	1.0828	1.0575
Int.		2B		1.0780	1.0650		1.0951	1.0889	1.1250
Ext.	1¹/₈-18 UNEF	3A	0.0000	1.1250	1.1163	-	1.0889	1.0853	1.0589
Int.		3B		1.0730	1.0650		1.0935	1.0889	1.1250
Ext.	1¹/₈-20 UN	2A	0.0014	1.1236	1.1155	-	1.0911	1.0866	1.0641
Int.		2B		1.0820	1.0710		1.0984	1.0925	1.1250
Ext.	1¹/₈-20 UN	3A	0.0000	1.1250	1.1169	-	1.0925	1.0891	1.0655
Int.		3B		1.0787	1.0710		1.0969	1.0925	1.1250
Ext.	1¹/₈-24 UNS	2A	0.0013	1.1237	1.1165	-	1.0966	1.0924	1.0742
Int.		2B		1.0900	1.0800		1.1034	1.0979	1.1250
Ext.	1¹/₈-28 UN	2A	0.0012	1.1238	1.1173	-	1.1006	1.0966	1.0812
Int.		2B		1.0950	1.0860		1.1070	1.1018	1.1250
Ext.	1¹/₈-28 UN	3A	0.0000	1.1250	1.1185	-	1.1018	1.0988	1.0824
Int.		3B		1.0926	1.0860		1.1057	1.1018	1.1250
Ext.	1³/₁₆-8 UN	2A	0.0021	1.1854	1.1704	-	1.1042	1.0972	1.0366
Int.		2B		1.0770	1.0520		1.1154	1.1063	1.1875
Ext.	1³/₁₆-8 UN	3A	0.0000	1.1875	1.1725	-	1.1063	1.1011	1.0387
Int.		3B		1.0672	1.0520		1.1131	1.1063	1.1875
Ext.	1³/₁₆-12 UN	2A	1.0017	1.1858	1.1744	-	1.1317	1.1259	1.0866
Int.		2B		1.1150	1.0970		1.1409	1.1334	1.1875
Ext.	1³/₁₆-12 UN	3A	0.0000	1.1872	1.1761	-	1.1334	1.1291	1.0883
Int.		3B		1.1073	1.0970		1.1390	1.1334	1.1875
Ext.	1³/₁₆-16 UN	2A	0.0015	1.1860	1.1766	-	1.1454	1.1403	1.1115
Int.		2B		1.1340	1.1200		1.1535	1.1469	1.1875
Ext.	1³/₁₆-16 UN	3A	0.0000	1.1875	1.1781	-	1.1469	1.1431	1.1130
Int.		3B		1.1283	1.1200		1.1519	1.1469	1.1875
Ext.	1³/₁₆-18 UNEF	2A	0.0015	1.1860	1.1773	-	1.1499	1.1450	1.1199
Int.		2B		1.1400	1.1270		1.1577	1.1514	1.1875
Ext.	1³/₁₆-18 UNEF	3A	0.0000	1.1875	1.1788	-	1.1514	1.1478	1.1214
Int.		3B		1.1355	1.1270		1.1561	1.1514	1.1875
Ext.	1³/₁₆-20 UN	2A	0.0014	1.1861	1.1780	-	1.1536	1.1489	1.1266
Int.		2B		1.1450	1.1330		1.1611	1.1550	1.1875
Ext.	1³/₁₆-20 UN	3A	0.0000	1.1875	1.1794	-	1.1550	1.1515	1.1280
Int.		3B		1.1412	1.1330		1.1595	1.1550	1.1875
Ext.	1³/₁₆-28 UN	2A	0.0012	1.1863	1.1798	-	1.1631	1.1590	1.1437
Int.		2B		1.1570	1.1490		1.1696	1.1643	1.1875
Ext.	1³/₁₆-28 UN	3A	0.0000	1.1875	1.1810	-	1.1643	1.1612	1.1449
Int.		3B		1.1551	1.1490		1.1683	1.1643	1.1875

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	=	Basic - Allowance, for Class 1A and 2A
	=	Basic for Class 3A

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