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Tap Size
Drill size
Aluminum, Copper & Copper alloys
Free cutting steel

Tap Size

 Drill Size
 Carbon & Alloy Steel, Heat Treated and Stainless

Diameter

Threads per inch

UNC

UNF

Drill Size

Decimal

Drill Size

Decimal
56 .0465 0   80nf 3/64 .0469
53 .0595 1 64nc   53 .0595
53 .0595   72nf 53 .0595
51 .0670 2 56nc   50 .0700
50 .0700   64nf 49 .0730
48 .0760 3 48nc   46 .0810
46 .0810   56nf 45 .0820
44 .0860 4 40nc   43 .089
43 .0890   48nf 42 .0935
39 .0995 5 40nc   38 .1015
38 .1015   44nf 37 .1040
36 .1065 6 32nc   7/64 .1094
33 .1130   40nf 32 .1160
29 .1360 8 32nc   29 .1360
29 .1360   36nf 28 .1405
26 .1470 10 24nc   24 .1520
5/32 .1562   32nf 21 .1590
11/64 .1719 12 24nc   16 .1770
15 .1800   28nf 14 .1820
8 .1990 1/4 20nc   6 .2040
3 .2130   28nf 7/32 .2188
F .2570 5/16 18nc   17/64 .2656
I .2720   24nf J .2770
5/16 .3125 3/8 16nc   P .3230
Q .3320   24nf R .3390
U .3680 7/16 14nc   3/8 .3750
W .3860   20nf 25/64 .3906
27/64 .4219 1/2 13nc   7/16 .4375
29/64 .4531   20nf 29/64 .4531
31/64 .4844 9/16 12nc   1/2 .5000
1/2 .5000   18nf 33/64 .5156
17/32 .5312 5/8 11nc   35/64 .5469
9/16 .5625   18nf 37/64 .5781
21/32 .6562 3/4 10nc   43/64 .6719
11/16 .6875   16nf 45/64 .7031
49/64 .7656 7/8 9nc   25/32 .7812
51/64 .7969   14nf 13/16 .8125
7/8 .8750 1 8nc   57/64 .8906
59/64 .9219   12nf 15/16 .9375
Run all drills 1/8" and smaller at high speed to prevent breaking If tapping hard or stainless steel use the proper tap and drill size
 Intermediate & Plug tap Click Here

To start cutting inside threads lube your hole with cutting oil and start the tap with lots of taper run this tap about 2 or 3 turns in then  back it out 1/4 turn lube your work go another 2 or three turns back it out 1/4 turn keeping your work wet with cutting fluid continue this method until you have completed the cut then use tap 2 the tap with the 2nd least amount of taper run this tap through using the same method as above then your final cut is with the  plug tap.

 This method is  a bit more work then driving a single tap through but if you have ever had a broken tap in a critical  piece of work you know what I'm talking about. if not take my word for it, it blows

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