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import drill_bit from ‘./drill_bit.png’ import tap from ‘./tap.png’

Drills and Taps

Think of it like this:

Drill: You use a drill to make a hole <img src={drill_bit} width=”400”/>
Tap: You use a tap to cut threads on the inside of that hole, so you can screw a bolt into it. <img src={tap} width=”400”/>

So, you drill the hole first, then tap it to add the threads.

O.D. (Outer Diameter): The width across the outside of an object. For a drill bit, it’s the width of the cutting part.
Tap (Tap Drill Size): The specific drill bit size used before threading a hole. Drill this hole first, then use a tap tool to cut threads.
Close Fit: A hole drilled just slightly larger than the bolt, so the bolt fits snugly.
Free Fit: A hole drilled larger than the bolt, allowing the bolt to pass through easily.

Screw Size Thread	O.D. Decimal	Tap Size	Decimal	Close Fit Size	Decimal	Free Fit Size	Decimal
000-120	0.0340	71	0.0260	65	0.0350	62	0.0380
00-90	0.0410	65	0.0350	3/64”	0.0469	55	0.0520
0-80	0.0600	3/64” (56)	0.0469	52	0.0635	50	0.0700
1-72	0.0730	53	0.0595	48	0.0760	46	0.0810
2-56	0.0860	50	0.0700	43	0.0890	41	0.0960
3-48	0.099	47	0.0790	37	0.1040	36	0.1065
4-40	0.1120	43	0.0890	32	0.1160	30	0.1285
5-40	0.125	38	0.102	29	0.1360	28 (9/64)	0.1405
6-32	0.1380	36	0.1065	27	0.1440	25	0.1495
8-32	0.1640	29	0.1360	18 (11/64)	0.1695	16	0.1770
10-24	0.190	25	0.150	9	0.196	7 (13/64)	0.2010
10-32	0.1900	21	0.1590	9	0.1960	7 (13/64)	0.2010
1/4-20	0.2500	7	0.2010	F	0.2570	H (17/64)	0.2660
1/4-28	0.2500	3	0.2130	F	0.2570	H (17/64)	0.2660
5/16-18	0.3125	F	0.2570	P	0.3230	Q	0.3320
3/8-16	0.3750	5/16”	0.3125	W	0.3860	X	0.3970
1/2-13	0.5000	27/64”	0.4219	33/64”	0.5156	17/32”	0.5312

*For copper, aluminum, cast iron, bakelite, or very thin materials, use one drill size larger (i.e. a slightly smaller diameter).

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