Tap Drill Sizes

Tap Drill Sizes for Metric Screw Threads

Tap Size	75% Thread			70% Thread			65% Thread
Tap Size	Theoretical Hole Size	Nearest Drill	Decimal Equivalent	Theoretical Hole Size	Nearest Drill	Decimal Equivalent	Theoretical Hole Size	Nearest Drill	Decimal Equivalent
M1.6 X 0.35	.0496	---	---	.0505	1.25mm	.0492	.0514	---	---
M2 X 0.40	.0634	---	---	.0644	1/16	.0625	.0654	52	.0635
M2.5 X 0.45	.0812	---	---	.0823	2.05mm	.0807	.0835	46	.0810
M3 X 0.50	.0989	---	---	.1002	40	.0980	.1015	39	.0995
M3 X 0.60	.0951	2.40mm	.0945	.0966	---	---	.0982	41	.0960
M3.5 X 0.60	.1148	33	.1130	.1163	2.90mm	.1142	.1178	32	.1160
M4 X 0.70	.1306	---	---	.1324	30	.1285	.1342	3.30mm	.1299
M4 X 0.80	.1268	---	---	.1288	1/8	.1250	.1309	3.25mm	.1280
M4.5 X 0.75	.1504	3.70mm	.1457	.1503	26	.1470	.1522	25	.1495
M5 X 0.80	.1662	---	---	.1682	4.20mm	.1654	.1703	---	---
M5 X 0.90	.1623	21	.1590	.1646	4.10mm	.1614	.1669	---	---
M6 X 0.75	.2074	13/64	.2031	.2094	5	.2055	.2113	5.30mm	.2087
M6 X 1.00	.1979	10	.1935	.2004	9	.1960	.2030	8	.1990
M7 X 1.00	.2372	A	.2340	.2398	6.00mm	.2362	.2423	B	.2380
M8 X 1.00	.2766	I	.2720	.2792	7.00mm	.2756	.2817	J	.2770
M8 X 1.25	.2670	6.70mm	.2638	.2702	17/64	.2656	.2734	6.80mm	.2677
M10 X 1.25	.3457	---	---	.3489	8.75mm	.3445	.3521	S	.3480
M10 X 1.50	.3362	8.40mm	.3307	.3400	8.50mm	.3346	.3438	---	---
M12 X 1.25	.4245	---	---	.4277	27/64	.4219	.4309	---	---
M12 X 1.75	.4053	10.25mm	.4035	.4098	13/32	.4062	.4143	---	---
M14 X 1.50	.4936	---	---	.4975	12.50mm	.4921	.5013	---	---
M14 X 2.00	.4745	15/32	.4688	.4796	12.00mm	.4724	.4847	---	---
M16 X 1.50	.5724	---	---	.5762	14.50mm	.5709	.5801	37/64	.5781
M16 X 2.00	.5532	35/64	.5469	.5583	14.00mm	.5512	.5634	---	---
M18 X 1.50	.6511	---	---	.6550	16.50mm	.6496	.6588	---	---
M18 X 2.00	.6319	---	---	.6371	---	---	.6422	41/64	.6406
M20 X 1.50	.7299	---	---	.7337	18.50mm	.7283	.7375	47/64	.7344
M20 X 2.50	.6915	11/16	.6875	.6979	---	---	.7043	---	---
M24 X 3.00	.8298	---	---	.8375	21.00mm	.8268	.8452	---	---
M30 X 3.50	1.0468	25.10mm	1.0394	1.0558	1 3/64	1.0469	1.0647	---	---

Notes:

Above are recommended tap drill sizes for cutting taps.
Hole sizes shown may not be suitable for UNJ and MJ hole requirements.
Oversize pitch diameters will need larger holes. Call the factory for assistance.

Tap Drill Formula

Hole size = Basic Major Diameter – 0.0130 X (Percent of Full Thread / Number of Threads per Inch)

Example: Find the nearest drill size for a 1/4-20 tap to produce 75% thread.

Hole size = 0.250 – 0.0130 x 75/20

Hole size = 0.250 – 0.049

Hole size = 0.2012 inches; the nearest drill is #8 (0.1990).

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