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.

On 1/11/2020 10:23 AM, 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.Â* 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.

Bob,

So, I was 3/4 way through reading your second paragraph. I started
to envision mounting your thingie in a lathe and drilling horizontally.
Then I got to your last paragraph and a smile came across my face. :-)

The one challenge is dialing in the elevation. But, I am guessing
you got that worked out with something in your shop.

Fun read!!! Thanks!!

Have a good rest of the weekend.

Les'

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.