Metric Tap Drill Sizes

In general, you can find the tap-drill for any size 60 degree thread, subtract one pitch length from the major diameter.

Formula: Major Dia. minus One Pitch Length equals tap-drill size

English Example for 3/8-16 thread: .375 - .0625 = .3125 tap-drill (5/16)

Metric Example for M6 X 1 thread: 6mm - 1mm = 5mm tap-drill

NOTE: The formula and the following Tap Drill Size Tables are only for cutting taps. Do not use this information for roll taps!

SCREW 
SIZE
DRILL 
SIZE MM
% THREAD NEAREST 
INCH DRILL
M1.6x.35
1.25
69%
3/64
M1.8x.35
1.45
69%
#53
M2x.4
1.60
69%
#52
M2.5x.45
2
69%
#46
M3x.5
2.50
68%
#40
M3.5x.6
2.90
68%
#33
M4x.7
3.30
69%
#30
M5x.8
4.20
69%
#19
SCREW 
SIZE
DRILL 
SIZE MM
% THREAD NEAREST 
INCH DRILL
M6x1
5.00
70%
#9
M7x1
6.00
70%
15/64
M8x1.25
6.70
74%
17/64
M8x1
7.00
69%
J
M10x1.5
8.50
71%
Q
M10x1.25
8.70
73%
11/32
M12x1.75
10.20
74%
Y
M12x1.25
1.80
67%
27/64
SCREW 
SIZE
DRILL 
SIZE MM
% THREAD NEAREST 
INCH DRILL
M14x2
12.00
72%
15/32
M14x1.5
12.50
71%
31/64
M16x2
14.00
72%
35/64
M16x1.5
14.50
71%
37/64
M18x2.5
15.50
73%
39/64
M18x1.5
16.50
70%
21/32
M20x2.5
17.50
73%
11/16
M20x1.5
18.50
70%
47/64
SCREW 
SIZE
DRILL 
SIZE MM
% THREAD NEAREST 
INCH DRILL


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