Tapping Sizes and Clearance Holes

Drill size and clearance hole recommendations  

All dimensions are recommendations only and are shown in mm.

Metric Threads

Thread Drill size for tapping standard metric threads Drill size for tapping fine metric threads Clearance hole
M1 0.75 - 1.2
M1.2 0.95 - 1.4
M1.4 1.1 - 1.6
M1.6 1.5 - 1.8
M1.8 1.4 - 2
M2 1.6 - 2.4
M2.2 1.7 - 2.8
M2.5 2 - 2.9
M3 2.5 - 3.4
M3.5 2.9 - 3.9
M4 3.3 - 4.5
M5 4.2 - 5.5
M6 5 - 6.6
M8 6.8 7 9
M10 8.5 8.8 11
M12 10.2 10.8 13.5
M14 12 12.5 15.5
M16 14 14.5 17.5
M18 15.5 16.5 20
M20 17.5 18.5 22
M22 19.5 20.5 24
M24 21 22 26
M27 24 25 30
M30 26.5 28 33

 

Unified Threads

Screw Size Threads per Inch Tapping Hole Clearance Hole
Aluminum, Brass, Plastic Ferrous Materials All Materials
Close Fit Free Fit
Drill Size Drill Size Drill Size Drill Size
0 80 3/64 55 52 50
1 64 53 1/16 48 46
72 53 52
2 56 50 49 43 41
64 50 48
3 48 47 44 37 35
56 45 43
4 40 43 41 32 30
48 42 40
5 40 38 7/64 30 29
44 37 35
6 32 36 32 27 25
40 33 31
8 32 29 27 18 16
36 29 26
10 24 25 20 9 7
32 21 18
12 24 16 12 2 1
28 14 10
32 13 9
1/4 20 7 7/32 F H
28 3 1
32 7/32 1
5/16 18 F J P Q
24 I 9/32
32 9/32 L
3/8 16 5/16 Q W X
24 Q S
32 11/32 T
7/16 14 U 25/64 29/64 15/32
20 25/64 13/32
28 Y Z
1/2 13 27/64 29/64 33/64 17/32
20 29/64 15/32
28 15/32 15/32
9/16 12 31/64 33/64 37/64 19/32
18 33/64 17/32
24 33/64 17/32
5/8 11 17/32 9/16 41/64 21/32
18 37/64 19/32
24 37/64 19/32
11/16 24 41/64 21/32 45/64 23/32
3/4 10 21/32 11/16 49/64 25/32
16 11/16 45/64
20 45/64 23/32
13/16 20 49/64 25/32 53/64 27/32
7/8 9 49/64 51/64 57/64 29/32
14 13/16 53/64
20 53/64 27/32
15/16 20 57/64 29/32 61/64 31/32
1 8 7/8 59/64 1-1/64 1-1/32
12 15/16 61/64
20 61/64 31/32
1-1/16 18 1.000 1-1/64 1-5/64 1-3/32
1-1/8 7 63/64 1-1/32 1-9/64 1-5/32
12 1-3/64 1-5/64
18 1-1/16 1-5/64
1-3/16 18 1-1/8 1-9/64 1-13/64 1-7/32
1-1/4 7 1-7/64 1-5/32 1-17/64 1-9/32
12 1-11/64 1-13/64
18 1-3/16 1-13/64
1-5/16 18 1-1/4 1-17/64 1-21/64 1-11/32
1-3/8 6 1-7/32 1-17/64 1-25/64 1-13/32
12 1-19/64 1-21/64
18 1-5/16 1-21/64
1-7/16 18 1-3/8 1-25/64 1-29/64 1-15/32
1-1/2 6 1-11/32 1-25/64 1-33/64 1-17/32
12 1-27/64 1-7/16
18 1-7/16 1-29/64
1-9/16 18 1-12 1-33/64 1-37/64 1-19/32
1-5/8 18 1-9/16 1-37/64 1-41/64 1-21/32
1-11/16 18 1-5/8 1-41/64 1-45/64 1-23/32
1-3/4 5 1-9/16 1-5/8 1-49/64 1-25/32

 



Note: Due to the fact that fastening applications differ greatly, the above information is for guidance only and is correct to the best of our knowledge. The customer must satisfy themselves with the performance of the fastener and validity of the data. TR Fastenings will not be held responsible for any failure that may occur from the use of this information.