On Fri, 30 Jul 2010 05:29:12 +1000, Why is everyone so cruel wrote:
"Dave__67" wrote
On Jul 29, 5:40 am, "Why is everyone so cruel" wrote:
I need to put about a 30 degree curve into a piece of sheet metal U
channel, curve needs to have a radius of 100mm.

Channel is 75mm wide x 15mm deep with 15mm flanges, made out of .75mm
sheet.

I dont have access to rollers - not sure how they'd be any use. I've
got an hydraulic press brake, plus usual workshop tools.

Any thoughts would be greatly appreciated.

First ? is- a curve which way?

Where the side walls form the inner and outer radii, or where the bottom
of the U is the inner or outer radius? [snip]

I added a layer of marks. (You should make your newsreader
indicate quotes by adding markers at left of quoted lines.)

As Simpson says "DOH"

The curve is across the open top of the U, The flanges to be welded onto
adjacent steel with the curve.

Your answer isn't perfectly clear to me, but I'm assuming the axis of
the bend is perpendicular to the long axis of the channel and that the
channel has a flat bottom 75mm wide which will bend "the easy way",
while the 15mm sides are bending "the hard way" and in compression.

How much crumpling of the sides can you tolerate? Crumpling will be
hard to avoid unless you have a tight-fitting steel die outside
the channel, and a tight-fitting 100mm-radius steel former inside the
channel, to form the bend on your press. If you make the die and
former with thick MDF, some crumpling probably would occur but might
be tolerable.

If you will be welding along the flanges anyway, you could cross cut
them half a dozen times in the bend region and then hand bend the base
of the channel to the right radius.

--
jiw