Tapping Drill Sizes | Coastal Fasteners

Tapping Drill Sizes

Metric ISO Fine

Size mm Pitch mm Tapping Drill Sizes
Preferred Alternative
mm Inch mm Inch
8.0 1.00 7.1 9/32 7.0
10.0 1.25 8.9 8.8 11/32
12.0 1.25 27/64 10.8
12.0 1.50 27/64 10.5
14.0 1.50 1/2 12.5
16.0 1.50 14.75 37/64 14.5
18.0 1.50 21/32 16.5
20.0 1.50 47/64 18.5
22.0 1.50 13/16 20.5
24.0 2.00 7/8 22.0

Metric ISO Coarse

Size mm Pitch mm Tapping Drill Sizes
Preferred Alternative
mm Inch mm Inch
2.0 0.40 1.6 1.6 1/16
2.5 0.45 2.1 2.05
3.0 0.50 2.55 2.5
3.5 0.60 2.95 2.9
4.0 0.70 3.4 3.3
4.5 0.75 3.8 3.7
5.0 0.80 4.3 11/64 4.2
6.0 1.00 5.1 13/64 5.0
7.0 1.00 6.1 6.0 15/64
8.0 1.25 6.9 6.8 17/64
9.0 1.25 7.9 5/16 7.8
10.0 1.50 8.6 11/32 8.5
11.0 1.50 9.5 3/8
12.0 1.75 13/32 10.2
14.0 2.00 12.2 31/64 12.0 15/32
16.0 2.00 14.25 9/16 14.0 35/64
18.0 2.50 15.75 15.5 39/64
20.0 2.50 45/64 17.5 11/16
22.0 2.50 25/32 19.5 49/64
24.0 3.00 21.0 53/64
27.0 3.00 61/64 24.0 15/16
30.0 3.50 26.5 1-3/64
33.0 3.50 1-11/64 29.5 1-5/32
36.0 4.00 1-17/64 32.0 1-1/4

UNC UNS*

Size Inch Threads per Inch Tapping Drill Sizes
Preferred Alternative
mm Inch mm Inch
No 2 56 1.85 1.8
No 3 48 2.1 2.05 5/64
No 4 40 2.35 3/32 2.3
No 5 40 2.65 2.6
No 6 32 2.85 2.8 7/64
No 8 32 3.5 3.4
No 10 24 3.9 5/32 3.8
No 12 24 4.5 4.4 11/64
1/8* 40 2.65 2.6
5/32* 32 3.3 3.1 1/8
3/16* 24 3.8 3.7
7/32* 24 4.6 4.5
1/4 20 5.2 13/64 5.1
5/16 18 6.6 17/64 6.5 1/4
3/8 16 8.1 8.0 5/16
7/16 14 9.5 3/8 23/64
1/2 13 11.0 10.8 27/64
9/16 12 12.2 31/64
5/8 11 13.8 35/64 13.5 17/32
11/16* 11 15.25 15.0 19/32
3/4 10 21/32 16.5 41/64
13/16* 10 23/32 18.0
7/8 9 19.5 49/64
1 8 7/8 22.5
1-1/8 7 25.0 63/64
1-1/4 7 1-7/64 28.0
1-3/8 6 31.0 1-7/32 1-13/64
1-1/2 6 1-11/32 34.0 1-21/64

UNF UNS*

Size Inch Threads per Inch Tapping Drill Sizes
Preferred Alternative
mm Inch mm Inch
No 5 44 2.7 2.65
No 6 40 2.95 2.9
No 8 36 3.6 9/64 3.5
No 10 32 4.1 4.0 5/32
No 12 28 4.7 4.6
1/8* 40 2.65 2.6
5/32* 32 3.3 3.1 1/8
3/16* 32 4.1 3.9 5/32
7/32* 32 4.9 4.8 3/16
1/4 28 5.5 7/32 5.4
5/16 24 6.9 6.8
3/8 24 8.5 8.4
7/16 20 10.0 25/64 9.8
1/2 20 11.5 29/64
9/16 18 33/64 12.8
5/8 18 14.5 37/64
11/16* 16 16.0 5/8 15.75
3/4 16 17.5 11/16
13/16* 16 3/4 19.0
7/8 14 13/16 20.5
1 12 23.5 59/64
1* 14 15/16 23.5
1 1/8 12 26.5 1 3/64
1 1/4 12 1 11/64 29.5
1 3/8 12 33.0 1 19/64
1 1/2 12 36.0 1 27/64

BSW Whitworth

Size Inch Threads per Inch Tapping Drill Sizes
Preferred Alternative
1/16* 60 1.2 3/64 1.05
3/32 48 1.9 1.75
1/8 40 2.55 2.5 3/32
5/32* 32 3.2 1/8 2.95
3/16 24 3.7 3.6 9/64
7/32 24 4.5 4.3 11/64
1/4 20 5.1 5.0 3/16
5/16 18 6.5 6.4 1/4
3/8 16 7.9 5/16 7.8 19/64
7/16 14 9.5 9.2 23/64
1/2 12 10.5 13/32
9/16 12 12 15/32
5/8 11 13.5 17/32 33/64
3/4 10 16.5 41/64 16.0 5/8
7/8 9 3/4 19.0 47/64
1 8 22.0 55/64 27/32
1-1/8 7 31/32 24.5 61/64
1-1/4 7 28.0 1-3/32 27.5 1-5/64
1-1/2 6 33.5 1-5/16 33.0 1-19/64
1-3/4 5 39.0 1-17/32 38.5 1-33/64
2 41/2 44.5 1-49/64 44.0 1-3/4

BSF

Size Pitch mm Tapping Drill Sizes
Preferred Alternative
mm Inch mm Inch
3/16 32 4.0 5/32 3.9
1/4 26 5.3 5.2 13/64
5/16 22 6.8 17/64 6.7
3/8 20 8.3 21/64 8.2 5/16
7/16 18 9.5 3/8
1/2 16 7/16 11.0 27/64
9/16 16 1/2 12.5 31/64
5/8 14 14.0 35/64 13.8 17/32
3/4 12 16.5 21/32
7/8 11 25/32 19.5 49/64
1 10 57/64 22.5 7/8
1-1/4 9 28.5 1-1/8 1-7/64
1-1/2 8 34.5 1-23/64 1-11/32
1-3/4 7 40.5 1-19/32 40.0 1-37/64

BSTP Taper Pipe

Size Inch Threads per Inch Tapping Drill Sizes
With Reamer Without Reamer
mm Inch mm Inch
1/8 28 8.0 5/16 8.4 21/64
1/4 19 10.8 27/64 11.2 7/16
3/8 19 14.25 9/16 14.75 37/64
1/2 14 45/64 23/32
3/4 14 23.0 29/32 15/16
1 11 29.0 1-9/64 30.0 1-11/64
1-1/4 11 37.5 1-15/32 38.5 1-33/64
1-1/2 11 43.5 1-23/32 44.5 1-3/4
2 11 2-5/32 2-3/16

BSPF Parallel Pipe

Size Inch Threads per Inch Tapping Drill Sizes
Preferred Alternative
mm Inch mm Inch
1/8 28 8.8 8.7 11/32
1/4 19 11.8 15/32 11.5 29/64
3/8 19 15.25 15.0 19/32
1/2 14 19.0 3/4 47/64
5/8 14 21.0 53/64 13/16
3/4 14 24.5 31/32 61/64
7/8 14 1-7/64 28.0
1 11 1-7/32 30.5
1-1/4 11 39.5 1-35/64 39.0
1-1/2 11 45.5 1-25/32 45.0 1-49/64
2 11 2-1/4
2-1/2 11 2-27/32
3 11 Hole size 3.369 - 3.344 inch

NPT Taper Pipe

Size Inch Threads per Inch Tapping Drill Sizes
With Reamer Without Reamer
mm Inch mm Inch
1/8 27 8.3 21/64 8.4
1/4 18 10.8 27/64 11.2 7/16
3/8 18 14.25 9/16 14.25 9/16
1/2 14 17.5 11/16 45/64
3/4 14 22.5 57/64 23.0 29/32
1 11-1/2 28.5 1-1/8 29.0 1-9/64
1-1/4 11-1/2 37.0 1-15/32 37.5 1-31/64
1-1/2 11-1/2 43.5 1-23/32 44.0 1-47/64
2 11-1/2 2-3/16 2-13/64