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  | N/F N/C Tap To Drill Size | | Metric Fine Metric Course Tap To Drill Size | | Self Tapping Screws | | Tap Drill Calculator |


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
26 .1470 3/16 24nc   (option)  3.7mm .1470
22 .1570   32nf   .1570
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

Material Drilling Tapping
Aluminum Soluble oil sulfur-based oil mixed with mineral oil 25/75 ratio (lathe work as well)
Brass Soluble oil lard oil with mineral oil 10/90 ratio
Bronze Soluble oil  lard with mineral oil 30/70 ratio
Alloy Steels Soluble oil lard oil with mineral oil 30/70 ratio
Cast Iron Dry Dry or  lard oil with  mineral oil 25/70 ratio
Malleable Iron Soluble oil Soluble oil
Copper Soluble oil Soluble oil
Low Carbon
& Tool Steels
Soluble oil lard oil with mineral oil 40/60 ratio
     

Center drill bit size

Gauge inches
BS1 1/8"
BS2 3/16"
BS3 1/4"
BS4 5/16"
BS5 7/16"
BS5A 1/2"
BS6 5/8"
BS7 3/4"

Milling Speeds High Speed Steel
 (HSS)

Aluminum 300
Brass & Bronze 150
Copper Soft 100
Cast Iron Soft 80
Cast Iron Hard 50
Mild Steel 90
Cast Steel 80
Alloy Steel hard 40
Tool Steel 50
Stainless Steel 60
Titanium 50
Plastics 300-800
Wood 300-500

This is a guide only tool size & configuration will vary tool speed. Carbide cutters can double the cutting speed.
Much faster speeds can be use with known techniques

Pipe Tap & Drill Size

NPT Size

 Drill Size

Decimal

1/16 - 27 "C" (0.242)
1/8 - 27 "Q"  (0.332)
1/4 - 18 7/16 (0.438)
3/8 - 18 9/16 (0.562)
1/2 - 14 45/64 (0.703)
3/4 - 14 29/32 (0.906)
1.0 - 11-1/2 1-9/64 (1.141)
1-1/4 - 11-1/2 1-31/64 (1.484)
1-1/2 - 11-1/2 1-23/32 (1.719)
2.0 - 11-1/2 2-3/16 (2.188)
2-1/2 - 8 2-39/64 (2.609)
3.0 - 8 3-15/64 (3.234)

 



29 for ACME threads.
 

60 for Vee threads

Square Thread

Centre gauge, fish tail gauge same thread gauge different name.

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

     
Acme  
Acme
Rough with finishing cut
     
     
     
Bottoming Tap  
Drill Tap  
Ext  
Fast Spiral  
Slow Spiral  
Interrupted Thread  
Standard  
Spiral Point  
Straight Pipe  
Taper Pipe Tap (NPT)  
Tandem Tap  
Taper  
Tru-flo  
Roll Forming  
  Nut Tap
     
     

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