These tapping drills are recommended for use on steel only and will give approx 75% depth of thread

 

SWG Thickness
Gauge	Ins (approx)	Ins (approx)	Metric (approx)
10swg	0.128"	1/8"	3.0mm
13swg	0.092"	3/32"	2.5mm
16swg	0.064"	1/16"	1.6mm
18swg	0.048"	3/64"	1.2mm
20swg	0.038"	n/a	0.97mm
22swg	0.028"	1/32"	0.71mm
24swg	0.022"	n/a	0.55mm
26swg	0.018"	n/a	0.46mm
28swg	0.0148"	1/64"	0.40mm

Brass Threads
Size inches	Threads/in	Tapping Drill		Clearance Drill
		mm.	No/Letter	mm.	No/Letter
1/4	26	5.6	2	6.6	G
9/32	26	6.35	E	7.5	M
5/16	26	7.15	K	8.2	P
3/8	26	8.8	S	9.8	W
7/16	26	10.3	Y	11.5	29/64
1/2	26	11.9	15/32	13.1	33/64

BSW Threads
Size inches	Threads/in	Tapping Drill		Clearance Drill
		mm.	No/Letter	mm.	No/Letter
1/16	60	1.15	58	1.70	49
3/32	48	1.9	49	2.5	36
1/8	40	2.6	38	3.3	29
5/32	32	3.2	31	4.1	19
3/16	24	3.8	26	4.9	9
7/32	24	4.6	15	5.7	1
1/4	20	5.2	7	6.5	G
5/16	18	6.6	F	8.2	P
3/8	16	8.0	O	9.8	W
7/16	14	9.3	U	11.5	29/64
1/2	12	10.7	27/64	13.1	33/64

BSF Threads
Size inches	Threads/in	Tapping Drill		Clearance Drill
		mm.	No/Letter	mm.	No/Letter
3/16	28	4.0		4.9
7/32	28	4.7	14	5.7	1
1/4	26	5.4	3	6.5	G
9/32	26	6.2	C	7.4	M
5/16	22	6.9	H	8.2	P
3/8	20	8.3	21/64	9.8	W
7/16	18	9.8	W	11.5	29/64
1/2	16	11.1	7/16	13.1	33/64

ME Threads
Size inches	Threads/In	Tapping Drill		Clearance Drill
		mm.	No/Letter	mm.	No/Letter
1/8	40	2.6	38	3.5	29
5/32	40	3.3	30	4.2	19
3/16	40	4.1	20	5.0	9
7/32	40	5.0	9	5.8	1
1/4	40	5.8	1	6.6	G
9/32	32	6.35	E	7.5	M
5/16	32	7.15	9/32	8.2	P
3/8	32	8.75	11/32	9.8	W
7/16	26	10.1	X	11.5	29/64
1/2	26	11.9	15/32	13.1	33/64

BA Threads
Number	Outside Diameter		Thread Pitch		Tapping Drill		Clearance Drill
	mm	Ins	mm	Threads/In	mm	No/Letter	mm	No/Letter
0	6.0	0.236	1.00	25.4	5.1	7	6.2	D
1	5.3	0.209	0.90	28.2	4.5	16	5.5	2
2	4.7	0.185	0.81	31.4	4.0	22	4.9	10
3	4.1	0.161	0.73	34.8	3.5	29	4.2	19
4	3.6	0.142	0.66	38.5	3.0	31	3.7	26
5	3.2	0.126	0.59	43.0	2.7	36	3.3	30
6	2.8	0.110	0.53	47.9	2.35	42	2.9	32
7	2.5	0.098	0.48	52.9	2.1	45	2.6	38
8	2.2	0.087	0.43	59.1	1.8	50	2.3	42
9	1.9	0.075	0.39	65.1	1.5	53	2.0	47
10	1.7	0.067	0.35	72.6	1.4	54	1.8	50
11	1.5	0.059	0.31	81.9	1.2	56	1.6	52
12	1.3	0.051	0.28	90.9	1.05	59	1.4	54
13	1.2	0.047	0.25	102.0	0.95	62	1.3	55
14	1.0	0.039	0.23	109.9	0.8	68	1.1	57
15	0.9	0.035	0.21	120.5	0.7	70	1.0	60
16	0.79	0.031	0.19	133.3	0.6	73	0.9	65

Decimal Equivalents Fractions of an inch expressed as decimals and millimetres
Fractional Inch	Decimal Inch	mm.	Fractional Inch	Decimal Inch	mm.
1/64	0.015625	0.3969	33/64	0.515625	13.0969
1/32	0.03125	0.7938	17/32	0.53125	13.4938
3/64	0.046875	1.1906	35/64	0.546875	13.8906
1/16	0.0625	1.5875	9/16	0.5625	14.2875
5/64	0.078125	1.9844	37/64	0.578125	14.6844
3/32	0.09375	2.3813	19/32	0.59375	15.0813
7/64	0.109375	2.7781	39/64	0.609375	15.4781
1/8	0.125	3.1750	5/8	0.625	15.8750
9/64	0.140625	3.5719	41/64	0.640625	16.2719
5/32	0.15625	3.9688	21/32	0.65625	16.6688
11/64	0.171875	4.3656	43/64	0.671875	17.0656
3/16	0.1875	4.7625	11/16	0.6875	17.4625
13/64	0.203125	5.1594	45/64	0.703125	17.8594
7/32	0.21875	5.5563	23/32	0.71875	18.2563
15/64	0.234375	5.9531	47/64	0.734375	18.6531
1/4	0.25	6.3500	3/4	0.75	19.0500
17/64	0.265625	6.7469	49/64	0.765625	19.4469
9/32	0.28125	7.1438	25/32	0.78125	19.8438
19/64	0.296875	7.5406	51/64	0.796875	20.2406
5/16	0.3125	7.9375	13/16	0.8125	20.6375
21/64	0.328125	8.3344	53/64	0.828125	21.0344
11/32	0.34375	8.7313	27/32	0.84375	21.4313
23/64	0.359375	9.1281	55/64	0.859375	21.8281
3/8	0.375	9.5250	7/8	0.875	22.2250
25/64	0.390625	9.9219	57/64	0.890625	22.6219
13/32	0.40625	10.3188	29/32	0.90625	23.0188
27/64	0.421875	10.7156	59/64	0.921875	23.4156
7/16	0.4375	11.1125	15/16	0.9375	23.8125
29/64	0.453125	11.5094	61/64	0.953125	24.2094
15/32	0.46875	11.9063	31/32	0.96875	24.6063
31/64	0.484375	12.3031	63/64	0.984375	25.0031
1/2	0.5	12.7000	1	1.0	25.4000

 

 

Disclaimer:

These tables have been reproduced here for the convienience of Model Engineers.
They are used entirely at your own risk.
No responsibilty can be accepted for any problems caused in there use.