Unified Threads Recommended Tapping Size & Clearance Holes

Unified Thread Recommended Tapping Drill and Clearance Hole Sizes

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Use these tables for calculating the relevant size drill bit and clearance hole for unified threads.

All dimensions are in millimeters (mm).

Screw Size		No. of Threads Per Inch	Minor Diameter	Tap Drills				Clearance Hole Drills - All Materials
				Aluminum, Brass & Plastics 75% Thread		Stainless Steel, Steels & Iron 50% Thread		Close Fit		Free Fit
No. or Diameter	Major Diameter			Drill Size	Decimal Equiv.	Drill Size	Decimal Equiv.	Drill Size	Decimal Equiv.	Drill Size	Decimal Equiv.
0	0.06	80	0.0447	3/64	0.0469	55	0.052	52	0.0635	50	0.07
1	0.073	64	0.0538	53	0.0595	1/16	0.0625	48	0.076	46	0.081
1	0.073	72	0.056	53	0.0595	52	0.0635	48	0.076	46	0.081
2	0.086	56	0.0641	50	0.07	49	0.073	43	0.089	41	0.096
2	0.086	64	0.0668	50	0.07	48	0.076	43	0.089	41	0.096
3	0.099	48	0.0734	47	0.0785	44	0.086	37	0.104	35	0.11
3	0.099	56	0.0771	45	0.082	43	0.089	37	0.104	35	0.11
4	0.112	40	0.0813	43	0.089	41	0.096	32	0.116	30	0.1285
4	0.112	48	0.0864	42	0.0935	40	0.098	32	0.116	30	0.1285
5	0.125	40	0.0943	38	0.1015	7/64	0.1094	30	0.1285	29	0.136
5	0.125	44	0.0971	37	0.104	35	0.11	30	0.1285	29	0.136
6	0.138	32	0.0997	36	0.1065	32	0.116	27	0.144	25	0.1495
8	0.164	32	0.1257	29	0.136	27	0.144	18	0.1695	16	0.177
8	0.164	36	0.1299	29	0.136	26	0.147	18	0.1695	16	0.177
10	0.19	24	0.1389	25	0.1495	20	0.161	9	0.196	7	0.201
10	0.19	32	0.1517	21	0.159	18	0.1695	9	0.196	7	0.201
12	0.216	24	0.1649	16	0.177	12	0.189	2	0.221	1	0.228
		28	0.1722	14	0.182	10	0.1935
		32	0.1777	13	0.185	9	0.196
1/4	0.25	20	0.1887	7	0.201	7/32	0.2188	F	0.257	H	0.266
		28	0.2062	3	0.213	1	0.228
		32	0.2117	7/32	0.2188	1	0.228
5/16	0.3125	18	0.2443	F	0.257	J	0.277	P	0.323	Q	0.332
		24	0.2614	I	0.272	9/32	0.2812
		32	0.2742	9/32	0.2812	L	0.29
3/8	0.375	16	0.2983	5/16	0.3125	Q	0.332	W	0.386	X	0.397
		24	0.3239	Q	0.332	S	0.348
		32	0.3367	11/32	0.3438	T	0.358
7/16	0.4375	14	0.3499	U	0.368	25/64	0.3906	29/64	0.4531	15/32	0.4687
		20	0.3762	25/64	0.3906	13/32	0.4062
		28	0.3937	Y	0.404	Z	0.413
1/2	0.5	13	0.4056	27/64	0.4219	29/64	0.4531	33/64	0.5156	17/32	0.5312
		20	0.4387	29/64	0.4531	15/32	0.4688
		28	0.4562	15/32	0.4688	15/32	0.4688
9/16	0.5625	12	0.4603	31/64	0.4844	33/64	0.5156	37/64	0.5781	19/32	0.5938
		18	0.4943	33/64	0.5156	17/32	0.5312
		24	0.5114	33/64	0.5156	17/32	0.5312
5/8	0.625	11	0.5135	17/32	0.5312	9/16	0.5625	41/64	0.6406	21/32	0.6562
		18	0.5568	37/64	0.5781	19/32	0.5938
		24	0.5739	37/64	0.5781	19/32	0.5938
11/16	0.6875	24	0.6364	41/64	0.6406	21/32	0.6562	45/64	0.7031	23/32	0.6562
3/4	0.75	10	0.6273	21/32	0.6562	11/16	0.6875	49/64	0.7656	25/32	0.7812
		16	0.6733	11/16	0.6875	45/64	0.7031
		20	0.6887	45/64	0.7031	23/32	0.7188
13/16	0.8125	20	0.7512	49/64	0.7656	25/32	0.7812	53/64	0.8281	27/32	0.8438
7/8	0.875	9	0.7387	49/64	0.7656	51/64	0.7969	57/64	0.8906	29/32	0.9062
		14	0.7874	13/16	0.8125	53/64	0.8281
		20	0.8137	53/64	0.8281	27/32	0.8438
15/16	0.9375	20	0.8762	57/64	0.8906	29/32	0.9062	61/64	0.9531	31/32	0.9688
1	1	8	0.8466	7/8	0.875	59/64	0.9219	1-1/64	1.0156	1-1/32	1.0313
		12	0.8978	15/16	0.9375	61/64	0.9531
		20	0.9387	61/64	0.9531	31/32	0.9688
1-1/16	1.0625	18	0.9943	1	1	1-1/64	1.0156	1-5/64	1.0781	1-3/32	1.0938
1-1/8	1.125	7	0.9497	63/64	0.9844	1-1/32	1.0313	1-9/64	1.1406	1-5/32	1.1562
		12	1.0228	1-3/64	1.0469	1-5/64	1.0781
		18	1.0568	1-1/16	1.0625	1-5/64	1.0781
1-3/16	1.1875	18	1.1193	1-1/8	1.125	1-9/64	1.1406	1-13/64	1.2031	1-7/32	1.2188
1-1/4	1.25	7	1.0747	1-7/64	1.1094	1-5/32	1.1562	1-17/64	1.2656	1-9/32	1.2812
		12	1.1478	1-11/64	1.1719	1-13/64	1.2031
		18	1.1818	1-3/16	1.1875	1-13/64	1.2031
1-5/16	1.3125	18	1.2443	1-1/4	1.25	1-17/64	1.2656	1-21/64	1.3281	1-11/32	1.3438
1-3/8	1.375	6	1.1705	1-7/32	1.2187	1-17/64	1.2656	1-25/64	1.3906	1-13/32	1.4062
		12	1.2728	1-19/64	1.2969	1-21/64	1.3281
		18	1.3068	1-5/16	1.3125	1-21/64	1.3281
1-7/16	1.4375	18	1.3693	1-3/8	1.375	1-25/64	1.3906	1-29/64	1.4531	1-15/32	1.4688
1-1/2	1.5	6	1.2955	1-11/32	1.3437	1-25/64	1.3906	1-33/64	1.5156	1-17/32	1.5312
		12	1.3978	1-27/64	1.4219	1-7/16	1.4375
		18	1.4318	1-7/16	1.4375	1-29/64	1.4531
1-9/16	1.5625	18	1.4943	1-12	1.5	1-33/64	1.5156	1-37/64	1.5781	1-19/32	1.5938
1-5/8	1.625	18	1.5568	1-9/16	1.5625	1-37/64	1.5781	1-41/64	1.6406	1-21/32	1.6562
1-11/16	1.6875	18	1.6193	1-5/8	1.625	1-41/64	1.6406	1-45/64	1.7031	1-23/32	1.7188
1-3/4	1.75	5	1.5046	1-9/16	1.5625	1-5/8	1.625	1-49/64	1.7659	1-25/32	1.7812

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