Thread References

Diameters of Unified Screw Threads UNC and UNF

Size Designation	Nominal Major Diameter (in)	Threads Per Inch
		Coarse Series UNC	Fine Series UNF
0	0.0600		80
1	0.0730	64	72
2	0.0860	56	64
3	0.0990	48	56
4	0.1120	40	48
5	0.1250	40	44
6	0.1380	32	40
8	0.1640	32	36
10	0.1900	24	32
12	0.2160	24	28
1/4	0.2500	20	28
5/16	0.3125	18	24
3/8	0.3750	16	24
7/16	0.4375	14	20
1/2	0.5000	13	20
9/16	0.5625	12	18
5/8	0.6250	11	18
3/4	0.7500	10	16
7/8	0.8750	9	14
1	1.0000	8	12
1-1/4	1.2500	7	12
1-1/2	1.5000	6	12
from Mechanical Engineering Design, 5th Ed, by Shigley & Mischke, McGraw-Hill, 1989, p 328

 

Diameters of Course-Pitch and Fine-Pitch Metric Threads
(All Dimensions in Millimeters)

Nominal Major Diameter	Pitch*			Nominal Major Diameter	Pitch*
	Coarse-Pitch Series	Fine-Pitch Series			Coarse-Pitch Series	Fine-Pitch Series
1.6	0.35			20	2.5	1.5
2	0.4			24	3	2
2.5	0.45			30	3.5	2
3	0.5			36	4	2
3.5	0.6			42	4.5	2
4	0.7			48	5	2
5	0.8			56	5.5	2
6	1			64	6	2
8	1.25	1		72	6	2
10	1.5	1.25		80	6	1.5
12	1.75	1.25		90	6	2
14	2	1.5		100	6	2
16	2	1.5		110		2

^*Pitch in US units is the reciprocal of the number of threads per inch.

from Mechanical Engineering Design, 5th Ed, by Shigley & Mischke, McGraw-Hill, 1989, p 327