Tap Size Question

[bertieng]

Any mod expert here can help informing what drill bit size I should use to make an opening for tapping 2.5mm?

Thanks.

[krustybrand]

Generally, you can subtract one pitch from the major diameter, so 2.5-.25= 2.25mm drill.

0.25mm pitch is the size for Daytona pushers (OEM).

Most tap drill charts only list the coarse metric threads and therefore show 2.05mm (2.5-0.45=2.05).

Try everything in a piece of scrap before committing to your watch case, just to be sure you get the correct thread depth.