As most of you know by now I make molds for a pretty small niche market.
Most of those molds are two piece (sometimes with inserts and other
things) that are placed together and held with clamping screws (or bar
clamps).

I also make some for gravity casting that are hinged with handles. For
the most part they are small enough I can drill the holes or spiral
interpolate for hinge pins on one of the CNC machines. Once in a while
I make one that is to big to set under a drill on any of the machines
except the drill press. My drill press is NOT a precision machine. I
made a steel jig that fits over the hinge boss of those molds. It gets
clamped in place, and a hand held drill is used to drill the hinge pin
holes. Its not great, but its better than the "big" drill press in the
shop. I know I need a decent drill press (or preferrably a taller
mill), but for now that's the solution. It has worked, and I don't have
to do it very often. Not often enough to spend the money on a better
quality drill press or bigger milling machine.

Well.... I have another tall hinged mold on the mill right now. 18.5
inches. I'm actually roughing the blank on one machine, and machining
the cavity on another due to speed and envelope limitations. It
actually took me a little while to get happy with my order of
operations, and I still have to hand drill the damned hinge pin holes.
I sure would like a better process for that.

Than I had an "aha" moment. My thoughts about gun drilling on the lathe
hold the answer. I have an MT4 adapter sleeve for the spindle, and an
MT4 ER32 collet chuck. Its time to develop my method for holding and
positioning stock on the carriage. For a one off I can probably just
use some of my assortment of right angle plates.