Tap Drill & Clearance Drill Chart

Tapping, forming-tap and clearance drills for Metric, UNC, UNF, BSW, BSF, BA, BSP, BSPT, NPT and NPS threads.

Tapping drill (~75% thread)Forming tap drill (~65%)Clearance drill

Clearance: ISO 273 medium fit (metric), free fit (inch). Forming-tap drills are a guide - check the tap maker's recommendation. Pipe threads: tapping drill only.

Metric threads

Metric Coarse (ISO M)

Thread	Pitch mm	Tap drill mm	Form mm	Clearance mm
M1	0.25	0.75	0.9	1.2
M1.2	0.25	0.95	1.1	1.4
M1.4	0.3	1.1	1.25	1.6
M1.6	0.35	1.25	1.45	1.8
M1.8	0.35	1.45	1.65	2.1
M2	0.4	1.6	1.8	2.4
M2.2	0.45	1.75	2	2.6
M2.5	0.45	2.05	2.3	2.9
M3	0.5	2.5	2.8	3.4
M3.5	0.6	2.9	3.25	3.9
M4	0.7	3.3	3.7	4.5
M4.5	0.75	3.75	4.15	5
M5	0.8	4.2	4.65	5.5
M6	1	5	5.55	6.6
M7	1	6	6.55	7.6
M8	1.25	6.75	7.45	9
M9	1.25	7.75	8.45	10
M10	1.5	8.5	9.35	11
M11	1.5	9.5	10.35	12
M12	1.75	10.25	11.25	13.5
M14	2	12	13.1	15.5
M16	2	14	15.1	17.5
M18	2.5	15.5	16.9	20
M20	2.5	17.5	18.9	22
M22	2.5	19.5	20.9	24
M24	3	21	22.65	26
M27	3	24	25.65	30
M30	3.5	26.5	28.45	33
M33	3.5	29.5	31.45	36
M36	4	32	34.25	39
M39	4	35	37.25	42
M42	4.5	37.5	40	45
M45	4.5	40.5	43	48
M48	5	43	45.8	52
M52	5	47	49.8	56
M56	5.5	50.5	53.55	62
M60	5.5	54.5	57.55	66
M64	6	58	61.35	70

Metric Fine (ISO MF)

Thread	Pitch mm	Tap drill mm	Form mm	Clearance mm
M6x0.75	0.75	5.25	5.65	6.6
M8x1	1	7	7.55	9
M8x0.75	0.75	7.25	7.65	9
M10x1.25	1.25	8.75	9.45	11
M10x1	1	9	9.55	11
M10x0.75	0.75	9.25	9.65	11
M12x1.5	1.5	10.5	11.35	13.5
M12x1.25	1.25	10.75	11.45	13.5
M12x1	1	11	11.55	13.5
M14x1.5	1.5	12.5	13.35	15.5
M16x1.5	1.5	14.5	15.35	17.5
M18x1.5	1.5	16.5	17.35	20
M20x1.5	1.5	18.5	19.35	22
M22x1.5	1.5	20.5	21.35	24
M24x2	2	22	23.1	26
M24x1.5	1.5	22.5	23.35	26
M27x2	2	25	26.1	30
M30x2	2	28	29.1	33
M30x1.5	1.5	28.5	29.35	33

British threads

BSW (British Standard Whitworth)

Thread	TPI	Tap drill mm	Clearance	mm
1/8"	40	2.5	#28	3.57
3/16"	24	3.6	#7	5.11
1/4"	20	5.1	H	6.76
5/16"	18	6.5	Q	8.43
3/8"	16	7.9	X	10.08
7/16"	14	9.3	15/32"	11.91
1/2"	12	10.5	17/32"	13.49
9/16"	12	12.1	39/64"	15.48
5/8"	11	13.5	43/64"	17.07
3/4"	10	16.5	13/16"	20.64
7/8"	9	19.25	29/32"	23.02
1"	8	22	1.1/32"	26.19
1.1/8"	7	24.75	1.5/32"	29.37
1.1/4"	7	27.75	1.9/32"	32.54
1.1/2"	6	33.5	1.17/32"	38.89
1.3/4"	5	39	1.25/32"	45.24
2"	4.1/2	44.5	2.1/32"	51.59

BSF (British Standard Fine)

Thread	TPI	Tap drill mm	Clearance	mm
3/16"	32	4	#7	5.11
7/32"	28	4.6	A	5.94
1/4"	26	5.3	H	6.76
9/32"	26	6.1	19/64"	7.54
5/16"	22	6.8	Q	8.43
3/8"	20	8.3	X	10.08
7/16"	18	9.7	15/32"	11.91
1/2"	16	11.1	17/32"	13.49
9/16"	16	12.7	39/64"	15.48
5/8"	14	14	43/64"	17.07
11/16"	14	15.5	23/32"	18.26
3/4"	12	16.75	13/16"	20.64
7/8"	11	19.75	29/32"	23.02
1"	10	22.75	1.1/32"	26.19
1.1/8"	9	25.75	1.5/32"	29.37
1.1/4"	9	28.75	1.9/32"	32.54
1.1/2"	8	34.5	1.17/32"	38.89

BA (British Association)

Thread	Pitch mm	Tap drill mm	Clearance mm
0BA	1.00	5.1	6.1
1BA	0.90	4.5	5.4
2BA	0.81	4	4.8
3BA	0.73	3.4	4.2
4BA	0.66	3	3.7
5BA	0.59	2.65	3.3
6BA	0.53	2.3	2.9
7BA	0.48	2.05	2.6
8BA	0.43	1.8	2.25
9BA	0.39	1.55	1.95
10BA	0.35	1.4	1.75

BSP / BSPP (G, parallel pipe)

Thread	TPI	Tap drill mm
1/8"	28	8.8
1/4"	19	11.8
3/8"	19	15.25
1/2"	14	19
5/8"	14	21
3/4"	14	24.5
7/8"	14	28.25
1"	11	30.75
1.1/4"	11	39.5
1.1/2"	11	45.25
2"	11	57

Pipe threads: tapping drill only.

BSPT (R / Rc, taper pipe)

Thread	TPI	Tap drill mm
1/8"	28	8.4
1/4"	19	11.2
3/8"	19	14.75
1/2"	14	18.25
3/4"	14	23.75
1"	11	30
1.1/4"	11	38.5
1.1/2"	11	44.5
2"	11	56

Tap drill without taper reamer. Pipe threads: tapping drill only.

American threads

UNC (Unified Coarse)

Thread	TPI	Tap drill	mm	Form mm	Clearance	mm
#1	64	#53	1.51	1.70	#46	2.06
#2	56	#50	1.78	2.00	#41	2.44
#3	48	#47	1.99	2.30	#35	2.79
#4	40	#43	2.26	2.55	#30	3.26
#5	40	#38	2.58	2.90	#29	3.45
#6	32	#36	2.71	3.15	#25	3.80
#8	32	#29	3.45	3.80	#16	4.50
#10	24	#25	3.80	4.35	#7	5.11
#12	24	#16	4.50	5.00	#1	5.79
1/4"	20	#7	5.11	5.80	H	6.76
5/16"	18	F	6.53	7.30	Q	8.43
3/8"	16	5/16"	7.94	8.80	X	10.08
7/16"	14	U	9.35	10.30	15/32"	11.91
1/2"	13	27/64"	10.72	11.85	17/32"	13.49
9/16"	12	31/64"	12.30	13.35	39/64"	15.48
5/8"	11	17/32"	13.49	14.85	43/64"	17.07
3/4"	10	21/32"	16.67	17.95	13/16"	20.64
7/8"	9	49/64"	19.45	21.00	29/32"	23.02
1"	8	7/8"	22.22	24.00	1.1/32"	26.19
1.1/8"	7	63/64"	25.00	26.95	1.5/32"	29.37
1.1/4"	7	1.7/64"	28.18	30.15	1.9/32"	32.54
1.3/8"	6	1.7/32"	30.96	33.05	1.13/32"	35.72
1.1/2"	6	1.11/32"	34.13	36.25	1.17/32"	38.89
1.3/4"	5	1.9/16"	39.69	42.20	1.25/32"	45.24
2"	4.1/2	1.25/32"	45.24	48.30	2.1/32"	51.59

UNF (Unified Fine)

Thread	TPI	Tap drill	mm	Form mm	Clearance	mm
#0	80	3/64"	1.19	1.40	#50	1.78
#1	72	#53	1.51	1.70	#46	2.06
#2	64	#50	1.78	2.00	#41	2.44
#3	56	#45	2.08	2.30	#35	2.79
#4	48	#42	2.37	2.60	#30	3.26
#5	44	#37	2.64	2.90	#29	3.45
#6	40	#33	2.87	3.20	#25	3.80
#8	36	#29	3.45	3.85	#16	4.50
#10	32	#21	4.04	4.50	#7	5.11
#12	28	#14	4.62	5.10	#1	5.79
1/4"	28	#3	5.41	5.95	H	6.76
5/16"	24	I	6.91	7.45	Q	8.43
3/8"	24	Q	8.43	9.05	X	10.08
7/16"	20	25/64"	9.92	10.55	15/32"	11.91
1/2"	20	29/64"	11.51	12.15	17/32"	13.49
9/16"	18	33/64"	13.10	13.65	39/64"	15.48
5/8"	18	37/64"	14.68	15.25	43/64"	17.07
3/4"	16	11/16"	17.46	18.35	13/16"	20.64
7/8"	14	13/16"	20.64	21.40	29/32"	23.02
1"	12	59/64"	23.42	24.45	1.1/32"	26.19
1.1/8"	12	1.3/64"	26.59	27.65	1.5/32"	29.37
1.1/4"	12	1.11/64"	29.77	30.80	1.9/32"	32.54
1.3/8"	12	1.19/64"	32.94	34.00	1.13/32"	35.72
1.1/2"	12	1.27/64"	36.12	37.15	1.17/32"	38.89

NPT (American taper pipe)

Thread	TPI	Tap drill	mm
1/16"	27	D	6.25
1/8"	27	R	8.61
1/4"	18	7/16"	11.11
3/8"	18	37/64"	14.68
1/2"	14	23/32"	18.26
3/4"	14	59/64"	23.42
1"	11.1/2	1.5/32"	29.37
1.1/4"	11.1/2	1.1/2"	38.10
1.1/2"	11.1/2	1.47/64"	44.05
2"	11.1/2	2.7/32"	56.36

Tap drill without taper reamer. Pipe threads: tapping drill only.

NPS (American straight pipe, NPSM)

Thread	TPI	Tap drill	mm
1/8"	27	S	8.84
1/4"	18	29/64"	11.51
3/8"	18	19/32"	15.08
1/2"	14	47/64"	18.65
3/4"	14	15/16"	23.81
1"	11.1/2	1.3/16"	30.16
1.1/4"	11.1/2	1.33/64"	38.50
1.1/2"	11.1/2	1.3/4"	44.45
2"	11.1/2	2.7/32"	56.36

Pipe threads: tapping drill only.