On 11/01/2020 15:23, Bob La Londe wrote:
As most of you know by now I make molds for a pretty small niche
market. Â*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.Â*
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.Â* 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.Â* My drill press is NOT a precision
machine.Â* I made a steel jig that fits over the hinge boss of those
molds.Â* It gets clamped in place, and a hand held drill is used to
drill the hinge pin holes.Â* Its not great, but its better than the
"big" drill press in the shop.Â* I know I need a decent drill press (or
preferrably a taller mill), but for now that's the solution.Â* It has
worked, and I don't have to do it very often.Â* 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.Â* I'm actually roughing the blank on one machine, and machining
the cavity on another due to speed and envelope limitations.Â* 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.Â* My thoughts about gun drilling on the
lathe hold the answer.Â* I have an MT4 adapter sleeve for the spindle,
and an MT4 ER32 collet chuck.Â* Its time to develop my method for
holding and positioning stock on the carriage.Â* For a one off I can
probably just use some of my assortment of right angle plates.

I needed to make some backing blocks for a pipe bender and wanted a
semicircular cut-out along the length, not something I could do on the
mill so opted for a between centres boring bar in the lathe. I made a T
slotted table which fixes to the cross slide on my Harrison M300Â* which
has the front and rear sides dovetailed so fixing the table in place was
easy and once set-up the job went very easily. I haven't used it since
but it sits in the tool store under the lathe tray until next needed.