Download the .pdf brochure Thread prehole table

Thread size	Hole size required for 6H tolerance (mm)			Hole size required for 6G tolerance (mm)
	75%	65%	55%	75%	65%	55%
M1.6 x 0.35	1.46	1.48	1.49	1.47	1.50	1.52
M2 x 0.40	1.83	1.85	1.87	1.86	1.88	1.90
M2.5 x 0.45	2.31	2.33	2.36	2.34	2.37	2.39
M3 x 0.50	2.79	2.81	2.84	2.82	2.84	2.87
M3.5 x 0.60	3.24	3.27	3.30	3.27	3.30	3.33
M4 x 0.70	3.68	3.72	3.75	3.72	3.75	3.78
M5 x 0.80	4.63	4.67	4.71	4.67	4.71	4.75
M6 x 1.00	5.54	5.59	5.64	5.57	5.62	5.67
M8 x 1.00	7.54	7.59	7.64	7.57	7.62	7.67
M8 x 1.25	7.40	7.46	7.52	7.44	7.50	7.57
M10 x 1.50	9.27	9.35	9.42	9.31	9.39	9.46
M12 x 1.50	11.27	11.35	11.42	11.31	11.39	11.46
M12 x 1.75	11.14	11.23	11.32	11.18	11.25	11.35
M14 x 1.50	13.27	13.35	13.42	13.31	13.39	13.46
M16 x 1.50	15.27	15.35	15.42	15.31	15.39	15.46

Thread size	Pre-hole size required for 2B tolerance (mm)
	75%	65%	55%
0-80	1.39	1.40	1.42
1-64	1.68	1.70	1.73
1-72	1.70	1.73	1.75
2-56	1.98	2.01	2.03
2-64	2.01	2.03	2.06
3-48	2.29	2.31	2.34
3-56	2.31	2.34	2.36
4-40	2.54	2.57	2.62
4-48	2.62	2.64	2.67
5-40	2.87	2.90	2.95
5-44	2.90	2.92	2.97
6-32	3.15	3.18	3.20
6-40	3.20	3.23	3.25
8-32	3.78	3.81	3.86
8-36	3.84	3.86	3.89
10-24	4.32	4.37	4.42
10-32	4.45	4.47	4.52
12-24	4.98	5.03	5.08
12-28	4.05	5.11	5.16
1/4-20	5.72	5.77	5.84
1/4-28	5.92	5.97	6.02
5/16-18	7.24	7.29	7.39
5/16-24	7.42	7.47	7.54
3/8-16	8.74	8.81	8.89
3/8-24	9.02	9.04	9.12
7/16-14	10.21	10.29	10.39
7/16-20	10.52	10.57	10.62
1/2-13	11.73	11.84	11.94
1/2-20	12.07	12.12	12.19
9/16-12	13.21	13.31	13.41
9/16-18	13.59	13.64	13.72
5/8-18	15.19	15.24	15.32