Thread Standards

Thread standards are established to ensure compatibility and facilitate maintenance. They can be based on metric or imperial measurement systems. Determining the correct thread type for existing and new applications is essential to ensure a proper joint connection

Here is a list of thread standards used in the industry:

• M (S.I.)             Regular pitch metric thread (international system).
• M (S.I.F.)          Fine pitch metric thread (international system).
• B.S.W. (W)       Regular pitch Whitworth thread.
• B.S.F.               Fine pitch Whitworth thread.
• U.N.C.              Regular pitch unified American thread.
• U.N.F.               Fine pitch unified American thread.
  

Regular pitch metric thread standards: M (S.I.)

Diameter		Pitch		Depth (mm)
(mm)	(inches)	(mm)	(inches)	Internal	External
0,3000	0,0118	0,0750	0,0030	0,0406	0,0460
0,4000	0,0157	0,1000	0,0039	0,0541	0,0613
0,5000	0,0197	0,1250	0,0049	0,0677	0,0767
0,6000	0,0236	0,1500	0,0059	0,0812	0,0920
0,8000	0,0315	0,2000	0,0079	0,1083	0,1227
1,0000	0,0394	0,2500	0,0098	0,1353	0,1534
1,2000	0,0472	0,2500	0,0098	0,1353	0,1534
1,4000	0,0551	0,3000	0,0118	0,1624	0,1840
1,6000	0,0630	0,3500	0,0138	0,1895	0,2147
1,7000	0,0669	0,3500	0,0138	0,1895	0,2147
1,8000	0,0709	0,3500	0,0138	0,1895	0,2147
2,0000	0,0787	0,4000	0,0157	0,2165	0,2454
2,2000	0,0866	0,4500	0,0177	0,2436	0,2760
2,3000	0,0906	0,4000	0,0157	0,2165	0,2454
2,5000	0,0984	0,4500	0,0177	0,2436	0,2760
2,6000	0,1024	0,4500	0,0177	0,2436	0,2760
3,0000	0,1181	0,5000	0,0197	0,2707	0,3067
3,5000	0,1378	0,6000	0,0236	0,3248	0,3680
4,0000	0,1575	0,7000	0,0276	0,3789	0,4294
4,5000	0,1772	0,7500	0,0295	0,4060	0,4601
5,0000	0,1969	0,8000	0,0315	0,4330	0,4907
5,5000	0,2165	0,9000	0,0354	0,4872	0,5521
6,0000	0,2362	1,0000	0,0394	0,5413	0,6134
7,0000	0,2756	1,0000	0,0394	0,5413	0,6134
8,0000	0,3150	1,2500	0,0492	0,6766	0,7668
9,0000	0,3543	1,2500	0,0492	0,6766	0,7668
10,0000	0,3937	1,5000	0,0591	0,8120	0,9201
11,0000	0,4331	1,5000	0,0591	0,8120	0,9201
12,0000	0,4724	1,7500	0,0689	0,9473	1,0735
14,0000	0,5512	2,0000	0,0787	1,0826	1,2268
16,0000	0,6299	2,0000	0,0787	1,0826	1,2268
18,0000	0,7087	2,5000	0,0984	1,3533	1,5335
20,0000	0,7874	2,5000	0,0984	1,3533	1,5335
22,0000	0,8661	2,5000	0,0984	1,3533	1,5335
24,0000	0,9449	3,0000	0,1181	1,6239	1,8402
27,0000	1,0630	3,0000	0,1181	1,6239	1,8402
30,0000	1,1811	3,5000	0,1378	1,8946	2,1469
33,0000	1,2992	3,5000	0,1378	1,8946	2,1469
36,0000	1,4173	4,0000	0,1575	2,1652	2,4536
39,0000	1,5354	4,0000	0,1575	2,1652	2,4536
42,0000	1,6535	4,5000	0,1772	2,4359	2,7603
45,0000	1,7717	4,5000	0,1772	2,4359	2,7603
48,0000	1,8898	5,0000	0,1969	2,7065	3,0670
52,0000	2,0472	5,0000	0,1969	2,7065	3,0670
56,0000	2,2047	5,5000	0,2165	2,9772	3,3737
60,0000	2,3622	5,5000	0,2165	2,9772	3,3737
64,0000	2,5197	6,0000	0,2362	3,2478	3,6804
68,0000	2,6772	6,0000	0,2362	3,2478	3,6804
72,0000	2,8346	6,0000	0,2362	3,2478	3,6804
76,0000	2,9921	6,0000	0,2362	3,2478	3,6804
80,0000	3,1496	6,0000	0,2362	3,2478	3,6804

• Depth in internal threads = 0.5413 x Pitch
• Depth in external threads = 0.6134 x Pitch

Fine pitch metric thread: M (S.I.F.)

Diameter		Pitch		Depth (mm)
(mm)	(inches)	(mm)	(inches)	Internal	External
1,0000	0,0394	0,2000	0,0079	0,1083	0,1227
1,2000	0,0472	0,2000	0,0079	0,1083	0,1227
1,4000	0,0551	0,2000	0,0079	0,1083	0,1227
1,7000	0,0669	0,2000	0,0079	0,1083	0,1227
2,0000	0,0787	0,2500	0,0098	0,1353	0,1534
2,3000	0,0906	0,2500	0,0098	0,1353	0,1534
2,5000	0,0984	0,3500	0,0138	0,1895	0,2147
2,6000	0,1024	0,3500	0,0138	0,1895	0,2147
3,0000	0,1181	0,3500	0,0138	0,1895	0,2147
3,5000	0,1378	0,3500	0,0138	0,1895	0,2147
4,0000	0,1575	0,5000	0,0197	0,2707	0,3067
4,5000	0,1772	0,5000	0,0197	0,2707	0,3067
5,0000	0,1969	0,5000	0,0197	0,2707	0,3067
6,0000	0,2362	0,7500	0,0295	0,4060	0,4601
7,0000	0,2756	0,7500	0,0295	0,4060	0,4601
8,0000	0,3150	1,0000	0,0394	0,5413	0,6134
9,0000	0,3543	1,0000	0,0394	0,5413	0,6134
10,0000	0,3937	1,0000	0,0394	0,5413	0,6134
12,0000	0,4724	1,2500	0,0492	0,6766	0,7668
13,0000	0,5118	1,5000	0,0591	0,8120	0,9201
14,0000	0,5512	1,5000	0,0591	0,8120	0,9201
16,0000	0,6299	1,5000	0,0591	0,8120	0,9201
18,0000	0,7087	1,5000	0,0591	0,8120	0,9201
20,0000	0,7874	1,5000	0,0591	0,8120	0,9201
22,0000	0,8661	1,5000	0,0591	0,8120	0,9201
24,0000	0,9449	2,0000	0,0787	1,0826	1,2268
27,0000	1,0630	2,0000	0,0787	1,0826	1,2268
30,0000	1,1811	2,0000	0,0787	1,0826	1,2268
33,0000	1,2992	2,0000	0,0787	1,0826	1,2268
36,0000	1,4173	3,0000	0,1181	1,6239	1,8402
39,0000	1,5354	3,0000	0,1181	1,6239	1,8402
42,0000	1,6535	3,0000	0,1181	1,6239	1,8402
45,0000	1,7717	3,0000	0,1181	1,6239	1,8402
48,0000	1,8898	3,0000	0,1181	1,6239	1,8402
52,0000	2,0472	3,0000	0,1181	1,6239	1,8402
56,0000	2,2047	4,0000	0,1575	2,1652	2,4536
60,0000	2,3622	4,0000	0,1575	2,1652	2,4536
64,0000	2,5197	4,0000	0,1575	2,1652	2,4536
68,0000	2,6772	4,0000	0,1575	2,1652	2,4536
72,0000	2,8346	4,0000	0,1575	2,1652	2,4536
76,0000	2,9921	4,0000	0,1575	2,1652	2,4536
80,0000	3,1496	4,0000	0,1575	2,1652	2,4536

Depth in internal threads = 0.5413 x Pitch
Depth in external threads = 0.6134 x Pitch

Whitworth thread standards with normal pitch: B.S.W. (W)

Thread			Pitch			Depth (mm)
	(mm)	(inches)	Edges	(mm)	(inches)	Internal	External
1/16	1,5875	0,0625	60	0,4233	0,0167	0,2710	0,2710
3/32	2,3812	0,0937	48	0,5292	0,0208	0,3388	0,3388
1/8	3,1750	0,1250	40	0,6350	0,0250	0,4066	0,4066
5/32	3,9687	0,1562	32	0,7938	0,0313	0,5083	0,5083
3/16	4,7625	0,1875	24	1,0583	0,0417	0,6776	0,6776
7/32	5,5562	0,2187	24	1,0583	0,0417	0,6776	0,6776
1/4	6,3500	0,2500	20	1,2700	0,0500	0,8132	0,8132
5/16	7,9375	0,3125	18	1,4111	0,0556	0,9035	0,9035
3/8	9,5250	0,3750	16	1,5875	0,0625	1,0165	1,0165
7/16	11,1125	0,4375	14	1,8143	0,0714	1,1617	1,1617
1/2	12,7000	0,5000	12	2,1167	0,0833	1,3553	1,3553
9/16	14,2875	0,5625	12	2,1167	0,0833	1,3553	1,3553
5/8	15,8750	0,6250	11	2,3091	0,0909	1,4785	1,4785
3/4	19,0500	0,7500	10	2,5400	0,1000	1,6264	1,6264
7/8	22,2250	0,8750	9	2,8222	0,1111	1,8071	1,8071
1	25,4000	1,0000	8	3,1750	0,1250	2,0330	2,0330
1 1/8	28,5750	1,1250	7	3,6286	0,1429	2,3234	2,3234
1 1/4	31,7500	1,2500	7	3,6286	0,1429	2,3234	2,3234
1 3/8	34,9250	1,3750	6	4,2333	0,1667	2,7106	2,7106
1 1/2	38,1000	1,5000	6	4,2333	0,1667	2,7106	2,7106
1 5/8	41,2750	1,6250	5	5,0800	0,2000	3,2527	3,2527
1 3/4	44,4500	1,7500	5	5,0800	0,2000	3,2527	3,2527
1 7/8	47,6250	1,8750	5	5,6444	0,2222	3,6141	3,6141
2	50,8000	2,0000	5	5,6444	0,2222	3,6141	3,6141
2 1/8	53,9750	2,1250	5	5,6444	0,2222	3,6141	3,6141
2 1/4	57,1500	2,2500	4	6,3500	0,2500	4,0659	4,0659
2 3/8	60,3250	2,3750	4	6,3500	0,2500	4,0659	4,0659
2 1/2	63,5000	2,5000	4	6,3500	0,2500	4,0659	4,0659
2 5/8	66,6750	2,6250	4	6,3500	0,2500	4,0659	4,0659
2 3/4	69,8500	2,7500	4	7,2571	0,2857	4,6467	4,6467
2 7/8	73,0250	2,8750	4	7,2571	0,2857	4,6467	4,6467
3	76,2000	3,0000	4	7,2571	0,2857	4,6467	4,6467
3 1/4	82,5500	3,2500	3	7,8154	0,3077	5,0042	5,0042
3 1/2	88,9000	3,5000	3	7,8154	0,3077	5,0042	5,0042
3 3/4	95,2500	3,7500	3	8,4667	0,3333	5,4212	5,4212
4	101,6000	4,0000	3	8,4667	0,3333	5,4212	5,4212
4 1/4	107,9500	4,2500	3	8,8348	0,3478	5,6569	5,6569
4 1/2	114,3000	4,5000	3	8,8348	0,3478	5,6569	5,6569
4 3/4	120,6500	4,7500	3	9,2364	0,3636	5,9141	5,9141
5	127,0000	5,0000	3	9,2364	0,3636	5,9141	5,9141

The threads must be defined in mm or inches. For example, to define a Whitworth thread with a 1/16 pitch, enter 1.5875 mm or 0.0625 inches.

The CNC calculates the pitch and the depth with the formulae:

• Pitch in mm = 25.4 / number of edges
• Pitch in inches = 1 / number of edges
• Depth in internal threads = 0,6403 x Pitch
• Depth in external threads = 0,6403 x Pitch

Whitworth thread with fine pitch: B.S.F

Thread			Pitch			Depth (mm)
	(mm)	(inches)	Edges	(mm)	(inches)	Internal	External
3/16	4,7625	0,1875	32	0,7937	0,0312	0,5082	0,5082
7/32	5,5562	0,2187	28	0,9071	0,0357	0,5808	0,5808
1/4	6,3500	0,2500	26	0,9769	0,0385	0,6255	0,6255
9/32	7,1437	0,2812	26	0,9769	0,0385	0,6255	0,6255
5/16	7,9375	0,3125	22	1,1545	0,0455	0,7392	0,7392
3/8	9,5250	0,3750	20	1,2700	0,0500	0,8132	0,8132
7/16	11,1125	0,4375	18	1,4111	0,0556	0,9035	0,9035
1/2	12,7000	0,5000	16	1,5875	0,0625	1,0165	1,0165
9/16	14,2875	0,5625	16	1,5875	0,0625	1,0165	1,0165
5/8	15,8750	0,6250	14	1,8143	0,0714	1,1617	1,1617
11/16	17,4625	0,6875	14	1,8143	0,0714	1,1617	1,1617
3/4	19,0500	0,7500	12	2,1167	0,0833	1,3553	1,3553
13/16	20,6375	0,8125	12	2,1167	0,0833	1,3553	1,3553
7/8	22,2250	0,8750	11	2,3091	0,0909	1,4785	1,4785
1	25,4000	1,0000	10	2,5400	0,1000	1,6264	1,6264
1 1/8	28,5750	1,1250	9	2,8222	0,1111	1,8071	1,8071
1 1/4	31,7500	1,2500	9	2,8222	0,1111	1,8071	1,8071
1 3/8	34,9250	1,3750	8	3,1750	0,1250	2,0330	2,0330
1 1/2	38,1000	1,5000	8	3,1750	0,1250	2,0330	2,0330
1 5/8	41,2750	1,6250	8	3,1750	0,1250	2,0330	2,0330
1 3/4	44,4500	1,7500	7	3,6286	0,1429	2,3234	2,3234
2	50,8000	2,0000	7	3,6286	0,1429	2,3234	2,3234
2 1/4	57,1500	2,2500	6	4,2333	0,1667	2,7106	2,7106
2 1/2	63,5000	2,5000	6	4,2333	0,1667	2,7106	2,7106
2 3/4	69,8500	2,7500	6	4,2333	0,1667	2,7106	2,7106
3	76,2000	3,0000	5	5,0800	0,2000	3,2527	3,2527

The threads must be defined in mm or inches. For example, to define a Whitworth thread with a 3/16 pitch, enter 4.7625 mm or 0.1875 inches.

The CNC calculates the pitch and the depth with the formulae:

• Pitch in mm = 25.4 / number of edges
• Pitch in inches = 1 / number of edges
• Depth in internal threads = 0,6403 x Pitch
• Depth in external threads = 0,6403 x Pitch

Regular pitch unified American thread: UNC (NC,USS)

Thread			Pitch			Depth (mm)
	(mm)	(inches)	Edges	(mm)	(inches)	Internal	External
0,0730	1,8542	0,0730	64	0,3969	0,0156	0,2148	0,2435
0,0860	2,1844	0,0860	56	0,4536	0,0179	0,2455	0,2782
0,0990	2,5146	0,0990	48	0,5292	0,0208	0,2865	0,3246
0,1120	2,8448	0,1120	40	0,6350	0,0250	0,3437	0,3895
0,1250	3,1750	0,1250	40	0,6350	0,0250	0,3437	0,3895
0,1380	3,5052	0,1380	32	0,7938	0,0313	0,4297	0,4869
0,1640	4,1656	0,1640	32	0,7938	0,0313	0,4297	0,4869
0,1900	4,8260	0,1900	24	1,0583	0,0417	0,5729	0,6492
0,2160	5,4864	0,2160	24	1,0583	0,0417	0,5729	0,6492
1/4	6,3500	0,2500	20	1,2700	0,0500	0,6875	0,7790
5/16	7,9375	0,3125	18	1,4111	0,0556	0,7638	0,8656
3/8	9,5250	0,3750	16	1,5875	0,0625	0,8593	0,9738
7/16	11,1125	0,4375	14	1,8143	0,0714	0,9821	1,1129
1/2	12,7000	0,5000	13	1,9538	0,0769	1,0576	1,1985
9/16	14,2875	0,5625	12	2,1167	0,0833	1,1458	1,2984
5/8	15,8750	0,6250	11	2,3091	0,0909	1,2499	1,4164
3/4	19,0500	0,7500	10	2,5400	0,1000	1,3749	1,5580
7/8	22,2250	0,8750	9	2,8222	0,1111	1,5277	1,7311
1	25,4000	1,0000	8	3,1750	0,1250	1,7186	1,9475
1 1/8	28,5750	1,1250	7	3,6286	0,1429	1,9642	2,2258
1 1/4	31,7500	1,2500	7	3,6286	0,1429	1,9642	2,2258
1 3/8	34,9250	1,3750	6	4,2333	0,1667	2,2915	2,5967
1 1/2	38,1000	1,5000	6	4,2333	0,1667	2,2915	2,5967
1 5/8	41,2750	1,6250	5	5,0800	0,2000	2,7498	3,1161
1 3/4	44,4500	1,7500	5	5,0800	0,2000	2,7498	3,1161
2	50,8000	2,0000	5	5,6444	0,2222	3,0553	3,4623
2 1/4	57,1500	2,2500	5	5,6444	0,2222	3,0553	3,4623
2 1/2	63,5000	2,5000	4	6,3500	0,2500	3,4373	3,8951
2 3/4	69,8500	2,7500	4	6,3500	0,2500	3,4373	3,8951
3	76,2000	3,0000	4	6,3500	0,2500	3,4373	3,8951

The threads must be defined in mm or inches. For example, to define an American thread with a 1/4 pitch, enter 6.3500 mm or 0.2500 inches.

The CNC calculates the pitch and the depth with the formulae:

• Pitch in mm = 25.4 / number of edges
• Pitch in inches = 1 / number of edges
• Depth in internal threads = 0.5413 x Pitch
• Depth in external threads = 0.6134 x Pitch

Fine pitch unified American thread: UNF (NF,SAE)

Thread			Pitch			Depth (mm)
	(mm)	(inches)	Edges	(mm)	(inches)	Internal	External
0,0600	1,5240	0,0600	80	0,3175	0,0125	0,1719	0,1948
0,0730	1,8542	0,0730	72	0,3528	0,0139	0,1910	0,2164
0,0860	2,1844	0,0860	64	0,3969	0,0156	0,2148	0,2435
0,0990	2,5146	0,0990	56	0,4536	0,0179	0,2455	0,2782
0,1120	2,8448	0,1120	48	0,5292	0,0208	0,2865	0,3246
0,1250	3,1750	0,1250	44	0,5773	0,0227	0,3125	0,3541
0,1380	3,5052	0,1380	40	0,6350	0,0250	0,3437	0,3895
0,1640	4,1656	0,1640	36	0,7056	0,0278	0,3819	0,4328
0,1900	4,8260	0,1900	32	0,7937	0,0312	0,4296	0,4869
19/88	5,4864	0,2160	28	0,9071	0,0357	0,4910	0,5564
1/4	6,3500	0,2500	28	0,9071	0,0357	0,4910	0,5564
5/16	7,9375	0,3125	24	1,0583	0,0417	0,5729	0,6492
3/8	9,5250	0,3750	24	1,0583	0,0417	0,5729	0,6492
7/16	11,1125	0,4375	20	1,2700	0,0500	0,6875	0,7790
1/2	12,7000	0,5000	20	1,2700	0,0500	0,6875	0,7790
9/16	14,2875	0,5625	18	1,4111	0,0556	0,7638	0,8656
5/8	15,8750	0,6250	18	1,4111	0,0556	0,7638	0,8656
3/4	19,0500	0,7500	16	1,5875	0,0625	0,8593	0,9738
7/8	22,2250	0,8750	14	1,8143	0,0714	0,9821	1,1129
1	25,4000	1,0000	12	2,1167	0,0833	1,1458	1,2984
1 1/8	28,5750	1,1250	12	2,1167	0,0833	1,1458	1,2984
1 1/4	31,7500	1,2500	12	2,1167	0,0833	1,1458	1,2984
1 1/2	38,1000	1,5000	12	2,1167	0,0833	1,1458	1,2984

The threads must be defined in mm or inches. For example, to define an American thread with a 1/4 pitch, enter 6.3500 mm or 0.2500 inches.

The CNC calculates the pitch and the depth with the formulae:

• Pitch in mm = 25.4 / number of edges
• Pitch in inches = 1 / number of edges
• Depth in internal threads = 0.5413 x Pitch
• Depth in external threads = 0.6134 x Pitch