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Calibration Resources

Tap Drill Chart

Tap Drill Sizes (inch) for a 75% Thread

In general, you can find the tap-drill for any size 60-degree thread, Subtract one pitch length from the major diameter.

Formula: Major Dia. minus One Pitch Length equals tap-drill size

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

0-80 UNF 3/64

1-64 UNC 53

1-72 UNF 53

2-56 UNC 50

2-64 UNF 50

3-48 UNC 47

3-56 UNF 45

4-40 UNC 43

4-48 UNF 42

5-40 UNC 38

5-44 UNF 37

6-32 UNC 36

6-40 UNF 33

8-32 UNC 29

8-36 UNF 29

10-24 UNC 25

10-32 UNF 21

12-24 UNC 16

12-28 UNF 14

14-20 UNS 10

14-24 UNS 7

1/4-20 UNC 7

Tap Size Thread Form Tap Drill

1/4-28 UNF 3

5/16-18 UNC F

5/16-24 UNF I

3/8-16 UNC 5/16

3/8-24 UNF Q

7/16-14 UNC U

7/16-20 UNF 25/64

1/2-13 UNC 27/64

1/2-20 UNF 29/64

9/16-12 UNC 31/64

9/16-18 UNF 33/64

5/8-11 UNC 17/32

5/8-18 UNF 37/64

11/16-11 UNS 19/32

11/16-16 UNS 5/8

3/4-10 UNC 21/32

3/4-16 UNF 11/16

7/8-9 UNC 49/64

7/8-14 UNF 13/16

1-8 UNC 7/8

1-12 UNF 59/64

1-14 UNS 15/16

Micro Precision Calibration Inc. is an ISO 17025 Accredited Lab that performs Calibration traceable to International Standards. We are ISO 9001:2005 Accredited and ANSI Z540 Compliant. This allows Micro Precision Calibration to provide state-of-the-art test equipment calibration services that precisely measure scale, flow, force, torque, weight, pressure, temperature, optical and calibrate almost any mechanical, electronic, or dimensional instrument.