Making a 38mm hole into a 40mm hole!

[chappers]

cut your 40mm hole in a bit of 6mm play with a hole saw.
Clamp it to your piece in the correct position and then use it as a guide for a 40mm forstner bit in a drill press. This is the easiest way to be cutting your holes anyway.

 

[ironsidebod]

Wouldn't be blind holes anymore though would they.

Oops! Yeah, teach me for posting without reading properly