Hi Team,
this scan from a Caterpillar Service Tools publication.

Also be aware that due to the ravages of time and so on that your Flat Seat Injector may have a different sized orifice to that stated here so maybe start with a small drill and work your way up gently and squarely.
As various engine size Valve Service groups became No Longer Available, Cat filled a Parts Order for one the in one size fits all category !!!

Cheers,
Eddie B.