Cherryville Chuck· Retired Moderator
Once you have the bit to the bottom of the collet there is nothing more to be gained. So if you remove the collet and measure it's length then that is the minimum insertion length for the bit shaft. It will be somewhere between about 19 and 25mm (my DeWalt 610 collet is only .7 something of an inch long). That's a clever little jig Harry made for keeping small straight bits from falling through.