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Tap Size (Inches) Drill Size (Fractional or Letter) Drill Size (Decimal Inches) (75% thread engagement)
-----------------------------------------------------------------------------------
0-80 #56 0.0465
1-64 #53 0.0595
2-56 #50 0.0700
3-48 #47 0.0785
4-40 #43 0.0890
5-40 #38 0.1015
6-32 #36 0.1065
8-32 #29 0.1360
10-24 #25 0.1495
12-24 #16 0.1770
1/4-20 F 0.2570
5/16-18 F 0.3125
3/8-16 5/16 0.3670
7/16-14 3/8 0.4219
1/2-13 27/64 0.4688
9/16-12 31/64 0.5156
5/8-11 17/32 0.5781
3/4-10 21/32 0.6563
7/8-9 49/64 0.7344
1-8 55/64 0.8281
Tap Size (Inches) Drill Size (Fractional or Letter) Drill Size (Decimal Inches) (75% thread engagement)
-----------------------------------------------------------------------------------
0-80 #56 0.0465
1-72 #53 0.0595
2-64 #50 0.0700
3-56 #45 0.0820
4-48 #42 0.0935
5-44 #37 0.1040
6-40 #33 0.1130
8-36 #29 0.1360
10-32 #21 0.1590
12-28 14 0.1820
1/4-28 #3 0.2130
5/16-24 F 0.2570
3/8-24 5/16 0.3125
7/16-20 11/32 0.3438
1/2-20 U 0.3680
9/16-18 31/64 0.4844
5/8-18 37/64 0.5781
3/4-16 5/8 0.6250
7/8-14 3/4 0.7500
1-12 7/8 0.8750