What tooling to drill lots of 10mm holes 45mm deep?

[irving2008]

Mike,

Do you think it would be possible to bore out the counter bore collar of something like this:

Trend CB58-14HSS 1/4 drill dia. x 5/8 counterbore

so it would take a 10mm drill? Is that madness?

It might be possible but
a) there'd be 2mm less thread for the locking grub screw which may be an issue; and
b) you'd probably need to bore/drill it out in a lathe for any degree of accuracy in run-out.