Home Standard Thread Specifications

Standard Thread Sizes

Standard Thread Specifications

Internal Threads

Thread Designation	Hole Diameter (in)	Max Thread Depth (in)
0 - 80 UNC	0.047	0.157
1 - 64 UNC	0.059	0.177
2 - 56 UNC	0.070	0.306
2 - 64 UNF	0.070	0.306
4 - 40 UNC	0.089	0.394
4 - 48 UNF	0.094	0.394
5 - 40 UNC	0.102	0.438
5 - 44 UNF	0.104	0.438
6 - 32 UNC	0.107	0.481
6 - 40 UNF	0.113	0.481
8 - 32 UNC	0.136	0.525
8 - 36 UNF	0.136	0.525
10 - 24 UNC	0.150	0.612
10 - 32 UNF	0.159	0.612
1/4 - 20 UNC	0.201	0.750
1/4 - 28 UNF	0.213	0.750
5/16 - 18 UNC	0.257	0.844
5/16 - 24 UNF	0.272	0.844
3/8 - 16 UNC	0.313	0.938
3/8 - 24 UNF	0.332	0.938
7/16 - 14 UNC	0.368	1.078
7/16 - 20 UNF	0.391	1.078
1/2 - 13 UNC	0.422	1.242
1/2 - 20 UNF	0.453	1.242
9/16 - 12 UNC	0.484	1.250
9/16 - 18 UNF	0.500	1.250
5/8 - 11 UNC	0.531	1.250
5/8 - 18 UNF	0.563	1.250
3/4 - 10 UNC	0.656	1.250
3/4 - 16 UNF	0.688	1.250

Standard Thread Specifications

Metric Thread Designation	Hole Diameter (in)	Max Thread Depth (in)
M2×0.4	0.063	0.306
M2.5×0.45	0.081	0.350
M3×0.5	0.098	0.438
M3.5×0.6	0.114	0.481
M4×0.7	0.130	0.525
M5×0.8	0.165	0.612
M6×1.0	0.197	0.750
M8×1.25	0.264	0.900
M10×1.5	0.335	0.938
M12×1.75	0.402	1.242

STI Threads

STI Thread Designation	Hole Diameter (in)	Max Thread Depth (in)
2-56 UNC	0.091	0.306
4-40 UNC	0.118	0.394
4-48 UNF	0.118	0.394
5-40 UNC	0.134	0.438
6-32 UNC	0.146	0.481
8-32 UNC	0.172	0.525
8-36 UNF	0.172	0.525
10-24 UNC	0.201	0.612
10-32 UNF	0.201	0.612
1/4-20 UNC	0.264	0.750
M2x0.4	0.083	0.306
M2.5x0.45	0.104	0.350
M3x0.5	0.126	0.438
M4x0.7	0.167	0.525
M5x0.8	0.209	0.612
M6x1.0	0.248	0.750
M8x1.25	0.331	0.900
M10x1.5	0.413	0.938
M12x1.75	0.492	1.242

External Threads

Thread Designation (UNC/UNF)	Boss Diameter (in)	Max Thread Length (in)
2-56 UNC	0.086	0.20
2-64 UNF	0.086	0.20
4-40 UNC	0.112	0.22
4-48 UNF	0.112	0.22
5-40 UNC	0.125	0.25
5-44 UNF	0.125	0.25
6-32 UNC	0.138	0.28
6-40 UNF	0.138	0.28
8-32 UNC	0.164	0.33
8-36 UNF	0.164	0.33
10-24 UNC	0.190	0.38
10-32 UNF	0.190	0.38
1/4-20 UNC	0.250	0.50
1/4-28 UNF	0.250	0.50
5/16-18 UNC	0.313	0.675
5/16-24 UNF	0.313	0.675
3/8-16 UNC	0.375	0.75
3/8-24 UNF	0.375	0.75
7/16-14 UNC	0.438	0.875
7/16-20 UNF	0.438	0.875
1/2-13 UNC	0.500	1.0
1/2-20 UNF	0.500	1.0
9/16-12 UNC	0.563	1.25
9/16-18 UNF	0.563	1.25
5/8-11 UNC	0.625	1.25
5/8-18 UNF	0.625	1.25
3/4-10 UNC	0.750	1.5
3/4-16 UNF	0.750	1.5
7/8-9 UNC	0.875	2.0
7/8-14 UNF	0.875	2.0
1"-8 UNC	1.000	2.5
1"-12 UNF	1.000	2.5

Metric External Threads

Metric Thread Designation	Boss Diameter (in)	Max Thread Length (in)
M2×0.4	0.079	0.276
M2.5×0.45	0.098	0.276
M3×0.5	0.118	0.276
M3.5×0.6	0.138	0.276
M4×0.7	0.157	0.500
M5×0.8	0.197	0.500
M6×1.0	0.236	0.500
M8×1.25	0.315	0.500
M10×1.5	0.394	1.000
M12×1.75	0.472	1.000
M14×2.0	0.551	1.500
M16×2.5	0.630	1.500
M24×3.0	0.945	2.000