Thread Data & Tapping Drill Size Comparison

Metric Coarse

Nom. Dia (mm)	Pitch (mm)	Tapping Drill (mm)
2.0	0.40	1.60
2.2	0.45	1.75
2.5	0.45	2.05
3.0	0.50	2.50
3.5	0.60	2.90
4.0	0.70	3.30
4.5	0.75	3.70
5.0	0.80	4.20
6.0	1.00	5.00
7.0	1.00	6.00
8.0	1.25	6.80
9.0	1.25	7.80
10.0	1.50	8.50
11.0	1.50	9.50
12.0	1.75	10.20
14.0	2.00	12.00
16.0	2.00	14.00
18.0	2.50	15.50
20.0	2.50	17.50
22.0	2.50	19.50
24.0	3.00	21.00
27.0	3.00	24.00
30.0	3.50	26.50
33.0	3.50	29.50
36.0	4.00	32.00
39.0	4.00	35.00
42.0	4.50	37.50
45.0	4.50	40.50
48.0	5.00	43.00
52.0	5.00	47.00
56.0	5.50	50.50
60.0	5.50	54.50

Metric Fine

Nom. Dia (mm)	Pitch (mm)	Tapping Drill (mm)
2.0	0.25	1.75
2.2	0.25	1.95
2.5	0.35	2.15
3.0	0.35	2.65
3.5	0.35	3.15
4.0	0.50	3.50
4.5	0.50	4.00
5.0	0.50	4.50
6.0	0.75	5.20
7.0	0.75	6.20
8.0	1.00	7.00
10.0	0.75	9.20
10.0	1.00	9.00
10.0	1.25	8.80
12.0	1.00	11.00
12.0	1.25	10.80
12.0	1.50	10.50
14.0	1.25	12.80
14.0	1.50	12.50
16.0	1.00	15.00
16.0	1.50	14.50
18.0	1.50	16.50
20.0	1.00	19.00
20.0	1.50	18.50
20.0	2.00	18.00
22.0	1.50	20.50
24.0	2.00	22.00
25.0	1.50	23.50
27.0	2.00	25.00
30.0	2.00	28.00
32.0	1.50	30.50
33.0	2.00	31.00
36.00	3.00	33.00
39.00	3.00	36.00

Table Key
Spark Plug
Metric Conduit

Unified Coarse

Size	Nom. Dia (Inch)	Pitch (T.P.I)	Tapping Drill (mm)
No.1	0.073	64	1.55
No.2	0.086	56	1.85
No.3	0.099	48	2.10
No.4	0.112	40	2.35
No.5	0.125	40	2.65
No.6	0.138	32	2.85
No.8	0.164	32	3.50
No.10	0.190	24	3.90
No.12	0.216	24	4.50
	1/4	20	5.10
	5/16	18	6.60
	3/8	16	8.00
	7/16	14	9.40
	1/2	13	10.80
	9/16	12	12.20
	5/8	11	13.50
	3/4	10	16.50
	7/8	9	19.50
	1	8	22.25
	1.1/8	7	25.00
	1.1/4	7	28.00
	1.3/8	6	30.75
	1.1/2	6	34.00
	1.3/4	5	39.50
	2	4.5	45.00

Unified Fine

Size	Nom. Dia (Inch)	Pitch (T.P.I)	Tapping Drill (mm)
No.0	0.060	80	1.25
No.1	0.073	72	1.55
No.2	0.086	64	1.90
No.3	0.099	56	2.15
No.4	0.112	48	2.40
No.5	0.125	44	2.70
No.6	0.138	40	2.95
No.8	0.164	36	3.50
No.10	0.190	32	4.10
No.12	0.216	28	4.70
	1/4	28	5.50
	5/16	24	6.90
	3/8	24	8.50
	7/16	20	9.90
	1/2	20	11.50
	9/16	18	12.90
	5/8	18	14.50
	3/4	16	17.50
	7/8	14	20.40
	1	12	23.25
	1.1/8	12	26.50
	1.1/4	12	29.50
	1.3/8	12	32.75
	1.1/2	12	36.00

British Standard Whitworth

Nom. Dia (Inch)	Pitch (T.P.I)	Tapping Drill (mm)
1/8	40	2.55
3/16	24	3.70
1/4	20	5.10
5/16	18	6.50
3/8	16	7.90
7/16	14	9.30
1/2	12	10.50
9/16	12	12.10
5/8	11	13.50
11/16	11	15.00
3/4	10	16.25
7/8	9	19.25
1	8	22.00
1.1/8	7	24.75
1.1/4	7	28.00
1.1/2	6	33.50
1.3/4	5	39.00
2	4.1/2	44.50
2.1/4	4	51.00
2.1/2	4	57.00
2.3/4	3.1/2	62.00
3	3.1/2	69.00

British Standard Fine

Nom. Dia (Inch)	Pitch (T.P.I)	Tapping Drill (mm)
3/16	32	3.70
7/32	28
1/4	26	5.10
9/32	26	6.50
5/16	22	6.50
3/8	20	7.90
7/16	18	9.30
1/2	16	10.50
9/16	16	12.10
5/8	14	13.50
11/16	14	15.00
3/4	12	16.25
7/8	11	19.25
1	10	22.00
1.1/8	9	24.75
1.1/4	9	28.00
1.3/8	8	33.50
1.1/2	8	33.50
1.5/8	8	39.00
1.3/4	7	39.00
2	7	44.50
2.1/4	6	51.00
2.1/2	6	57.00
2.3/4	6	62.00
3	5	69.00

British Standard Pipe

Nom. Dia (Inch)	Pitch (T.P.I)	Tapping Drill (mm)
1/8	28	8.80
1.4	19	11.80
3/8	19	15.25
1/8	14	19.00
5/8	14	21.00
3/4	14	24.50
7/8	14	28.25
1	11	30.75
1.1/4	11	39.50
1.1/2	11	45.00
1.3/4	11	51.00
2	11	57.00

British Association

Size	Pitch (mm)	Tapping Drill (mm)
No.0	1.00	5.10
No.1	0.90	4.50
No.2	0.81	4.00
No.3	0.73	3.40
No.4	0.66	3.00
No.5	0.59	2.65
No.6	0.53	2.30
No.7	0.48	2.05
No.8	0.43	1.80
No.9	0.39	1.55
No.10	0.35	1.40
No.11	0.31	1.20
No.12	0.28	1.05
No.13	0.25	0.98
No.14	0.23	0.8

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