According to Mike Henry :
"Bill Schwab" wrote in message
...
Hello all,
I need to make a hole for a D-shell connector in a plastic box, approx
6x3x2 inches. It is at least simlar to Radio Shack cataglog number
270-1803 (you can search for that number on www.radioshack.com in case you
want see what I have in mind), and I need to put the trapezoidal hole in
one of the ends.
Any thoughts on clamping the box such that the end suspended above the
table of a mill-drill is well supported? I suppose I could simply clamp
it in the vice, but that seems less than optimal.
There are punches for making D-shell holes, but the last I looked, each
size cost almost half what I paid for my mill (minus tooling, freight,
etc. g).
Yes -- D-shaped Greenlee chassis punches are only nice if you
have them. Also -- some plastics might shatter on an attempt to punch
them with such a tool.
Obviously, once I clamp the box, I will have the joys of trying to machine
something that has non-orthogonal sides. One approach would be to put the
rotary base back on my vice. I could make a jig of some sort, or simply
get the corners right and fake the non-parallel edges. Given that I have
previously done this by hand with a dremel, it need not be perfect. With
that said, suggestions for doing it correctly will be cheerfully read and
quite possible used.
I'd be inclined to clamp it directly to the table and use some blocks of
scrap and machinist jacks inside the case to support the top solidly. That
general idea seemed to work well for some rectangular openings I milled in a
12" Hoffman box a while back.
Since this is plastic, I think that what I would do is to take
some sacrificial lumber -- perhaps a chunk of 4x4 cut to near length, and
put it inside the box to fully support the surface which you are
cutting. Then put some straps of metal or more (thinner -- say perhaps
1/2" thick) wood on top, and apply the hold-down clamps to that surface.
Then mill through the top wood, the plastic, and a little way
into the support wood, and you should have the plastic fairly well
supported and unlikely to crack. If the position of the hole is not too
critical, draw it out on the top piece of wood, and mill to that line.
Good Luck,
DoN.
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