STI : Tap Drill Sizes

Tap Drill Sizes for Screw Thread Insert (STI) Taps

Tap Size	Drill Size Aluminum	Drill Size Steel, Magnesium, Plastic
2-56	3/32	41
3-48	36	7/64
3-56	37	36
4-40	31	31
4-48	3.0 mm	31
5-40	3.4 mm	29
6-32	26	25
6-40	26	25
8-32	17	16
8-36	17	16
10-24	13/64	5
10-32	7	13/64
12-24	1	1
1/4-20	H	H
1/4-28	G	6.7 mm
5/16-18	Q	Q
5/16-24	21/64	21/64
3/8-16	X	X
3/8-24	25/64	25/64
7/16-14	29/64	29/64
7/16-20	29/64	29/64
1/2-13	33/64	17/32
1/2-20	29/64	29/64
9/16-12	37/64	19/32
9/16-18	37/64	37/64
5/8-11	21/32	21/32
5/8-18	41/64	41/64
3/4-10	25/32	25/32
3/4-16	49/64	49/64
7/8-9	29/32	29/32
7/8-14	57/64	57/64
1-8	1 1/32	1 1/32
1-12	1 1/64	1 1/64

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