"William Bagwell" wrote in message
...
Back working on my bat house mold. Envision a large rectangular sink made
of
5/16 thick cast aluminum... I'm 'milling' a shallow slot in the middle
with out
a milling machine. A router with a carbide bit actually works (slowly!) as
long
as I take light cuts and keep it lubed up with stick wax. Running into a
problem getting the slots all the way into the corners.

http://www.mysecondbathouse.com/smal...mold-slots.jpg

Have already booked some run time at my local rotational molder next month
and
would like to connect the slots before then. Only real machine shop I can
possibly afford (semi retired relative) is not open on my normal days off
and
my day job is oddly wide a** open. Running out of time and ideas so I'm
asking
here.
--
William


Even if you had a mill, you probably could not make that cut all the way
into the corner.

Some one else suggested using a cold chisel which might be the best option
in your situation, although it might not look so pretty.

Other options could be:
1. Cut the sides off, then mill the slots, then screw, weld or braze back
together.
2. If you did not mind making the part smaller and had not already milled
most of the slot, you could have welded or screwed in sheets of aluminum to
raise the flat surface rather than mill the slot.
3. Make a jig to guide a hand-held dremel or die grinder. You could either
use an end-cutting bit or an abrasive cutting wheel. It depends which corner
you want the radius to be on.
4. Cut out the center section containing the slot. Weld in place a thinner
piece to form the slot.

BTW, I assume you know that the vertical edges of the slot should be angled
slightly to let the part pop out of the mold more easily.