On Fri, 08 Feb 2013 14:20:55 -0600, Jon Elson wrote:

Stormin Mormon wrote:

Bend first, punch holes later?
Where accuracy of hole placement on the final, bent piece is tight, then
this is the only way to do it. If .05" is acceptable, then you CAN do
it by milling/punching it flat and bending after. You may have to make a
test article and bend, then adjust the work stop for additional parts.
You may need to do this "bend calibration" step for each batch of
aluminum. You will also need to make sure EACH piece of aluminum is
oriented with the rolling "grain" in the same direction. Once set up
and calibrated like that, you can probably hold .020" tolerance pretty
consistently, if the brake is in good shape.

I do this sort of stuff in a home shop with well-used equipment, and it
works out pretty well. But, if the hole location relative to the bend
is critical, I bend first, then machine.

Actually, I can easily design the piece so that the absolute height of
the holes can vary by 1/4 inch up or down -- it's just the relative
height that's important, so that a shaft stuck through them is more or
less level to the bottom.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com