It seems as though the fixture clamps are toe-type pieces that are actually
clamping down on the rolled edge of the lid/workpiece.

Having a groove in the fixture baseplate for the rolled edge to partially
rest in, might be one feature that could be added fairly easily.

I prefer to have some backing material inside thinwall objects or materials
(typically plastic or sheetmetal workpieces), such as a plywood disk or ring
(pvc pipe section) placed inside the lid to give more wall support.

Wood backup material may be acceptable for 50 pieces, but I'm not familiar
with how hardwood or plywood reacts to flood lubricant/coolant.

Radiused internal aluminum pieces, secured to the baseplate would likely be
better for a longer production run, mounted in a way as to not have the
cutting tool run into a hardened screw head.

What function are the circuit boards when they're finished?

--
WB
..........


"steamer" wrote in message
...
I've got a situation where I have to drill 3 holes, then accurately
cut out a slot in the lid of a small cookie tin. I made the fixture
pictured
here to do the deed:
http://www.flickr.com/photos/steambo...57624880649814
--The trick I came up with: I layed the thing out with a measuring
tape, making certain that the center of the round thing was a little over
some nice round numbers in X and Y, relative to a reference corner. Once
everything was drilled, tapped and fastened in place I put the fixture in
the vise with a part mounted. Using a dial indicator that touched the
outer
rim I found the exact center of the part. I reset my DRO to 0,0 here and
then went looking for the edge of the fixture with an edge finder. I
marked
down the numbers, then milled those two edges to 'round out' the
distances.
Next time I use the fixture I know the center of the round thing is
exactly
6" in X and 2" in Y, instead of some weird number I'd never remember.
--Still and all I'm not real happy with the fixture and I'd be
interested to know what others may have done in similar situations. I
didn't
want to go overboard on design since I'm only doing maybe 50 of these and
the 'customer' is me. ;-)

--
"Steamboat Ed" Haas : Steel, Stainless, Titanium:
Hacking the Trailing Edge! : Guaranteed Uncertified Welding!
www.nmpproducts.com
---Decks a-wash in a sea of words---