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Taps, dies and drills


Tap and drill sizes

To find the correct drill size for tapping a thread, simply subtract the core diameter from the thread size. The most common thread sizes are given in the table.

Metric Course Threads
Diam. core tapping drill clearance drill
4.0 3.14 3.3 4.1
5.0 4.02 4.2 5.1
6.0 4.77 5.0 6.1
8.0 6.47 6.8 8.2
10.0 8.16 8.5 10.2
12.0 9.85 10.2 12.2
14.0 11.55 12.0 14.25
16.0 13.55 14.0 16.25
20.0 16.93 17.5 20.25

For more tables I recommend buying the Zeus book. I also use the Presto book.

Zeus and Presto books, well used

 


Drilling speeds

It is important to select a suitable speed when drilling. Softer materials are drilled at higher speeds, deeper holes should be drilled at lower speed.