Re: Machining on Opposite Sides

Thanks for all the thoughtful suggestions. I've given the problem a
lot of time thinking about it and decided there are tradeoffs in time
in any situation. The part, about 3" by 3" and 1.5" thick will be cut
out of a piece of aluminum 48"L by 3"W by 1.5"T and can have about
80% of its machining done on one side. I decided the easiest way of
going about it is to do all the inside pocketing along with drilling
first, doing about 6 parts at a time in one row. Then bolt all the
pieces through a center hole in each directly to the T slots. Then do
the perimeter machining and parting off leaving an edge to do a full
length finish cut. Then finally do the perimeter finish cut.

Since most of the metal removal is already accomplished on 6 parts at
a time I can afford to make a jig for the other side of the part and
do them one at a time. With the jig, using the advice of using a 'L'
support on the 2 flat side, it will be easy to fix the Part Zero at
the corner of the 'L'. Not quite as elegant a solution as some of the
suggestions but I think equally fast or more so. Thanks for the help.

Eric

--- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:
> exeric1 wrote:
>
> > I'm confronted with the problem of machining two sides of the same
> > material. The piece is irregular on its perimeter dimension, that
is
> > not square or rectangular or round. I'd like to reference the part
> > zero on side 1 on side 2 and perhaps just mirror some of the
> > commands. I'm trying to avoid having to use edge finders and such
on
> > the opposite side to find the same part zero on the other side.
The
> > part has 2 flat sides on its perimeter that meet at 90 degrees
with a
> > large fillet between them. I'm using the imaginary point where the
> > two lines would meet without the fillet as my part zero on side 1.
> >
> > I'm using locating pins along the two flat sides to locate the
part
> > and fix the part zero. Any easy way to go about this? I'm going
to be
> > making many of these parts and I don't want to have to fuss over
it
> > every time I turn the part over.
>
> Sure. Make what I call a 'sacrificial' and our shop calls a 'scab
plate'.
> You take a piece of scrap and drill holes for dowel pins and or
clamping
> bolts. You mount the part for the first side, machine, then flip it
> over. You might use different holes for the dowels or clamp bolts.
>
> One other possibility is to make a fixture with a part-shaped
> hole in it, and some fingers that bolt onto the fixture that holds
the
> part from one side. Then, you have more fingers on the other side
> that grip the part when you tighten thumbscrews. You machine
> one side, and then flip the entire fixture over for the other
side. This
> leaves both entire faces clear except where the fingers are.
>
> Jon