October 1. 2006
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Tap and Drill Chart

For 75% thread depth use this chart.

Tap size Correct drill size Closest fractional bit size Decimal equivalant
0-80 NF 3/64" 3/64" .0469
1-72 #53 1/16" .0595
3-48 #47 5/64" .0785
4-40 #43 3/32" .0890
4-48 #42 3/32" .0935
6-32 #35 7/64" .1100
8-36 #29 9/64" .1360
8-32 #29 9/64" .1360
10-24 #25 5/32" .1495
10-32 #21 5/32" .1590
12-24 #16 11/64" .1770
12-28 #14 3/16" .1820
1/4"-20 #7 13/64" .2010
1/4"-28 #3 7/32" .2130
1/4"-32 7/32" <--- .2188
5/16"-18 letter F 17/64" .2570
5/16"-24 17/64" <--- .2656
3/8"-16 5/16" <--- .3125
3/8"-24 letter Q 21/64" .3320
7/16"-14 letter U 23/64" .3680
7/16"-20 25/64" <--- .3906
1/2"-13 27/64" <--- .4219
1/2"-20 29/64" <--- .4531
1/2"-24 29/64" <--- .4531
9/16"-12 31/64" <--- .4844
9/16"-18 33/64 <--- .5156
5/8"-11 17/32" <--- .5312
5/8"-18 37/64" <--- .5781
11/16"-11 19/32" <--- .5938
11/16"-16 5/8" <--- .6250
3/4"-10 21/32" <--- .6562
3/4"-16 11/16" <--- .6875

Cutting Fluid

Use of the proper cutting lubricant will make better threads and prolong tap and die service life. For small holes in thin materials you can get away without any lube.
Material to be tapped Lube to use
aluminum kerosene
brass kerosene
bronze kerosene
steel cutting oil
stainless steel kerosene mixed with cutting oil
hardwood dry

Clearance Drill Sizes

Screw or bolt nominal size Clearance drill size
#0 51
#1 47
#3 36
#4 31
#6 25
#8 16
#10 13/64"
#12 7/32"
1/4" 17/64"
5/16" 21/64"
3/8" 25/64"
7/16" 29/64"