RECOMMENDED TAPPING DRILL SIZE

Use these tables/charts for working out the relevant size drill bit for taps.

Drill size recommendations.

All dimensions are shown in millimetres (mm).

ISO Metric Coarse Thread

Size Pitch Drill
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

ISO Metric Fine Thread

Size Pitch Drill
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 1.5 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