Recommended Tapping Drill Size

ISO Metric Coarse

Size (mm) Pitch (mm) Drill (mm)
M1 .25 .75
M1.1 .25 .85
M1.2 .25 .95
M1.4 .3 1.1
M1.6 .35 1.25
M1.8 .35 1.45
M2 .4 1.6
M2.2 .45 1.75
M2.5 .45 2.05
M3 .5 2.5
M3.5 .6 2.9
M4 .7 3.3
M4.5 .75 3.75
M5 .8 4.2
M6 1 5
M7 1 6
M8 1.25 6.75
M9 1.25 7.75
M10 1.5 8.5
M11 1.5 9.5
M12 1.75 10.2
M14 2 12
M16 2 14
M18 2.5 15.5
M20 2.5 17.5
M22 2.5 19.5
M24 3 21
M27 3 24
M30 3.5 26.5
M33 3.5 29.5
M36 4 32
M39 4 35
M42 4.5 37.5
M45 4.5 40.5
M48 5 43
M52 5 47
M56 5.5 50.5
M60 5.5 54.5
M64 6 58
M68 6 62
M72 6 66
M76 6 70

BSF

Size No.
or inch		 Pitch
TPI		 Drill (mm)
3/16 32 5.00
1/4 26 6.60
5/16 22 8.30
3/8 20 9.90
7/16 18 11.60
1/2 16 13.00
9/16 16 14.80
5/8 14 16.40
11/16 14 17.70
3/4 12 19.60
7/8 18 16.25
1″ 10 26.50

BS. Brass

Size No.
or inch		 Pitch
TPI		 Drill (mm)
1/4 26 6.50
5/16 26 8.10
3/8 26 9.70
7/16 26 11.30
1/2 26 12.90

ISO Metric Fine

Size (mm) Pitch (mm) Drill (mm)
M2 .25 1.75
M2.2 .25 1.95
M2.3 .25 2.05
M2.5 .35 2.15
M2.6 .35 2.25
M3 .35 2.65
M3.5 .35 3.15
M4 .35 3.65
M4 .5 3.5
M5 .35 4.65
M5 .5 4.5
M5 .75 4.25
M5.5 .5 5
M6 .5 5.5
M6 .75 5.25
M7 .75 6.25
M8 .5 7.5
M8 .75 7.25
M8 1 7
M9 .75 8.25
M9 1 8
M10 .5 9.5
M10 .75 9.25
M10 1 9
M10 1.25 8.75
M11 .75 10.25
M11 1 10
M11 1.25 9.75
M12 .5 11.5
M12 .75 11.25
M12 1 11
M12 1.25 10.75
M12 1.5 10.5
M14 1 13
M14 1.25 12.75
M14 1.5 12.5
M15 .75 14.25
M15 1 14
M15 1.5 13.5
M16 .5 15.5
M16 .75 15.25
M16 1 15
M16 1.25 14.75
M16 1.5 14.5
M17 1 16
M17 1.5 15.5
M18 .75 17.25
M18 1 17
M18 1.25 16.75
M18 1.5 16.5
M18 2 16
M19 1 18
M20 1 19
M20 1.5 18.5
M20 2 18
M22 1 21
M22 1.5 20.5
M22 2 20
M24 1 23
M24 1.5 22.5
M24 2 22
M25 1 24
M25 1.5 23.5
M25 2 23
M27 1 26
M27 1.5 25.5
M27 2 25
M28 1 27
M28 1.5 26.5
M28 2 26
M30 1 29
M30 1.5 28.5
M30 2 28
M30 3 27
M32 1 31
M32 1.5 30.5
M32 2 30
M33 1.5 31.5
M33 2 31
M33 3 30
M35 1.5 33.5
M35 2 33
M35 3 32
M36 1 35
M36 1.5 34.4
M36 2 34
M36 3 33
M38 1 37
M38 1.5 36.5
M38 2 36
M39 1.5 37.5
M39 2 37
M39 3 36
M40 1 39
M40 1.5 38.5
M40 3 37
M42 1.5 40.5
M42 2 40
M42 3 39
M42 4 38
M45 1.5 43.5
M45 2 43
M45 3 42
M48 1.5 46.5
M48 2 46
M48 3 45
M48 4 44
M50 1.5 48.5
M50 2 48
M50 3 47
M52 1.5 50.5
M52 2 50
M52 3 49
M52 4 48
M56 2 54
M56 4 52

UNC

Size No.
or inch		 Pitch
TPI		 Drill (mm)
#1 64 1.55
#2 56 1.85
#3 48 2.1
#4 40 2.35
#5 40 2.65
#6 32 2.85
#8 32 3.5
#10 24 3.9
#12 24 4.5
1/4 20 5.1
5/16 18 6.6
3/8 16 8
7/16 14 9.4
1/2 13 10.8
9/16 12 12.2
5/8 11 13.5
3/4 10 16.5
7/8 9 19.5
1 8 22.25
1 1/8 7 25
1 1/4 7 28
1 3/8 6 30.75
1 1/2 6 34
1 3/4 5 39.5
2 4.5 45
2 1/4 4.5 51.5
2 1/2 4 57.25
2 3/4 4 63.5
3 4 70

G (BSP)

Size No.
or inch		 Pitch
TPI		 Drill (mm)
1/8 26 10.00
1/4 19 13.60
3/8 19 17.10
1/2 14 21.50
5/8 14 23.40
3/4 14 27.00
7/8 14 30.60
1″ 11 33.70

UNx8

Size No.
or inch		 Pitch
TPI		 Drill (mm)
1 1/8 8 28.75
1 1/4 8 31.75
1 3/8 8 35.00
1 1/2 8 38.00
1 5/8 8 41.50
1 3/4 8 44.50
1 7/8 8 47.75
2″ 8 50.90

UNF

Size No.
or inch		 Pitch
TPI		 Drill (mm)
#0 80 1.25
#1 72 1.55
#2 64 1.9
#3 56 2.15
#4 48 2.4
#5 44 2.7
#6 40 2.95
#8 36 3.5
#10 32 4.1
#12 28 4.7
1/4 28 5.5
5/16 24 6.9
3/8 24 8.5
7/16 20 9.9
1/2 20 11.5
9/16 18 12.9
5/8 18 14.5
3/4 16 17.5
7/8 14 20.4
1 12 23.25
1 1/8 12 26.5
1 1/4 12 29.5
1 3/8 12 32.75
1 1/2 12 36

BA

Size No.
or inch		 Pitch
TPI		 Drill (mm)
0 25.40 6.20
2 31.35 4.90
4 38.48 3.80
6 47.92 2.90

BSW

Size No.
or inch		 Pitch
TPI		 Drill (mm)
1/8 40 3.40
3/16 24 5.10
1/4 20 6.70
5/16 18 8.30
3/8 16 9.90
7/16 14 11.60
1/2 12 13.00
9/16 12 14.80
5/8 11 16.70
11/16 11 17.80
3/4 10 20.00
7/8 9 23.00
1″ 8 26.50

All information is strictly informative