Guide 05 · Fastener Reference Guide

Conversion Charts — Tapping Drills

Tapping drill sizes for metric, UNC, UNF and BSW threads.

Text version — searchable and screen-reader friendly

Tapping Drill Tables Metric Threads, Coarse & Fine Pitch (Dimensions in mm)

Diameter	Coarse Pitch	Fine Pitch	Tapping Hole
M2	0.4	–	1.60
M2.5	0.45	–	2.05
M3	0.5	–	2.50
M3.5	0.6	–	2.90
M4	0.7	–	3.30
M4.5	0.75	–	3.70
M5	0.8	–	4.20
M6	1	–	5.00
M8	1.25	–	6.80
M10	1.5	–	8.50
M10	–	1.25	8.80
M12	1.75	–	10.20
M12	–	1.25	10.80
M12	–	1.5	10.50
M14	2	–	12.00
M14	–	1.5	12.50
M16	2	–	14.00
M16	–	1.5	14.50
M18	2.5	–	15.50
M18	–	1.5	16.50
M20	2.5	–	17.50
M20	–	1.5	18.50
M22	2.5	–	19.50
M22	–	1.5	20.50
M24	3	–	21.00
M24	–	1.5	22.50
M24	–	2	22.00
M27	3	–	24.00
M30	3.5	–	26.50
M33	3.5	–	29.50
M36	4	–	32.00

Diameter	UNC	UNF	BSW
# 0	–	80	–
# 1	64	72	–
# 2	56	64	–
# 3	48	56	–
# 4	40	48	–
# 5	40	44	–
# 6	32	40	–
# 8	32	36	–
# 10	24	32	–
# 12	24	28	–
1/4	20	28	20
5/16	18	24	18
3/8	16	24	16
7/16	14	20	14
1/2	13	20	12
9/16	12	18	12
5/8	11	18	11
3/4	10	16	10
7/8	9	14	9
1	8	12 (14)	8
1 1/8	7	12	7
1 1/4	7	12	7
1 3/8	6	12	6
1 1/2	6	12	6
1 5/8	–	–	5
1 3/4	5	–	5
1 7/8	–	–	–
2	4.5	–	4.5
2 1/4	4.5	–	4
2 1/2	4	–	3.5
2 3/4	4	–	3.25

Imperial (Inches)	Metric (mm)	Imperial (Inches)	Metric (mm)
1/64	0.397	1	25.4
1/32	0.794	1 - 1/4	31.75
3/64	1.19	1 - 3/8	34.93
1/16	1.587	1 - 1/2	38.1
5/64	2	1 - 3/4	44.45
3/32	2.381	2	50.8
7/64	2.778	2 - 1/4	57.15
1/8	3.175	2 - 1/2	63.5
9/64	3.571	2 - 3/4	69.85
5/32	3.968	3	76.2
11/64	4.365	3 - 1/4	82.55
3/16	4.762	3 - 1/2	88.9
13/64	5.159	4	101.6
7/32	5.556	4 - 1/2	114.3
15/64	5.953	4 - 3/4	120.7
1/4	6.35	5	127
17/64	6.746	5 - 1/2	139.7
9/32	7.143	6	152.4
19/64	7.54	6 - 1/2	165.1
5/16	7.937	7	177.8
21/64	8.334	7 - 1/2	190.5
11/32	8.731	8	203.2
23/64	9.128	9	228.6
3/8	9.525	10	254
25/64	9.921	10-1/4	260.35
13/32	10.318	10-1/2	266.7
27/64	10.715	10-3/4	273.05
7/16	11.112	11	279.4
29/64	11.509	11-1/4	285.75
15/32	11.908	11-1/2	292.1
31/64	12.303	11-3/4	298.45
1/2	12.7	12	304.8
33/64	13.097
17/32	13.494
35/64	13.891
9/16	14.288
37/64	14.684
19/32	15.081
39/64	15.478
5/8	15.875
41/64	16.272
21/32	16.669
43/64	17.066
11/16	17.462
45/64	17.859
23/32	18.256
47/64	18.653
3/4	19.05
49/64	19.447
25/32	19.844
51/64	20.241
13/16	20.638
53/64	21.034
27/32	21.431
55/64	21.828
7/8	22.225
57/64	22.622
29/32	23.019
59/64	23.416
15/16	23.812
61/64	24.209
31/32	24.606
63/64	25.003

Diameter	Coarse Thread	Fine Thread	Extra Fine Thread
M1.6	0.35	0.20	–
M2	0.40	0.25	–
M2.5	0.45	0.35	–
M3	0.50	0.35	–
M3.5	0.60	–	–
M4	0.70	0.50	–
M5	0.80	0.50	–
M6	1.00	0.75	–
M8	1.25	1.00	0.75
M10	1.50	1.25	1.00
M12	1.75	1.50	1.25
M14	2.00	1.50	1.25
M16	2.00	1.50	1.00
M18	2.50	1.50	–
M20	2.50	2.00	1.50
M22	2.50	2.00	–
M24	3.00	2.00	1.50
M27	3.00	2.00	–
M30	3.50	2.00	–
M33	3.50	2.00	–
M36	4.00	3.00	–
M39	4.00	3.00	–
M42	4.50	4.00	–
M45	4.50	4.00	–
M48	5.00	4.00	–
M52	5.00	4.00	–
M56	5.50	4.00	–
M60	5.50	4.00	–
M64	6.00	4.00	–
M72	6.00	4.00	–