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Tap Drill Size

Tap Drill Sizes (inch) for a 75% Thread

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

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

Tap Size Thread Form Tap Drill   Tap Size Thread Form Tap Drill   Tap Size Thread Form Tap Drill
0-80 UNF 3/64   10-24 UNC 25   1/2-20 UNF 29/64
1-64 UNC 53   10-32 UNF 21   9/16-12 UNC 31/64
1-72 UNF 53   12-24 UNC 16   9/16-18 UNF 33/64
2-56 UNC 50   12-28 UNF 14   5/8-11 UNC 17/32
2-64 UNF 50   14-20 UNS 10   5/8-18 UNF 37/64
3-48 UNC 47   14-24 UNS 7   11/16-11 UNS 19/32
3-56 UNF 45   1/4-20 UNC 7   11/16-16 UNS 5/8
4-40 UNC 43   1/4-28 UNF 3   3/4-10 UNC 21/32
4-48 UNF 42   5/16-18 UNC F   3/4-16 UNF 11/16
5-40 UNC 38   5/16-24 UNF I   7/8-9 UNC 49/64
5-44 UNF 37   3/8-18 UNC 5/16   7/8-14 UNF 13/16
6-32 UNC 36   3/8-20 UNF Q   1-8 UNC 7/8
6-40 UNF 33   7/16-14 UNC U   1-12 UNF 59/64
8-32 UNC 29   7/16-20 UNF 25/64   1-14 UNS 15/16
8-36 UNF 29   1/2-13 UNC 27/64