[TheForge] Bending steel

[ries]

Are you tryint to bend flat bar in one plane, or sheet in two?
That is, a simple curve in flat bar, the easy way, is, well easy.
But curving sheet into a 3 dimensional bowl shaped curve is harder.

Neither is impossible- like Grant says- Cheap, fast, or good- pick one
(Well, he actually says, pick two- but thats often not realistic)

I bend 1/8" steel into curves in one plane all the time. Depending on  
size, I use my hossfeld, which will accomodate up to 4" wide material,  
or my 4' wide power rolls, which will, obviously roll material up to  
four feet wide.

Now, if you want spherical sections, that gets a lot harder.
The ways they do this in industry are either huge presses- for 1/8",  
200 to 1000 tons would be used, with big male and female dies, which  
are machined from huge blocks. This is how they make the ends for tanks
Or- they use a hammer- for 1/8", cold, that would be a pretty big  
power planishing hammer. Most 50 to 100 lb (thats ram weight) hammers  
will form domes in material up to around 16 gage. I have two friends  
who have mechanical hammers like this that were used to make domed  
tops for beer brewing kettles, from copper.
Or- they use mondo english wheels. The sculpture Cloud Gate, in  
Chicago, the big stainless steel bean, is made from 1/8" to 3/8" thick  
stainless plate, rolled on a massive english wheel, which was custom  
built for the project.

The cheap workaround is usually to build this up from smaller sections  
of material, that are either flat, like a soccer ball, or that are  
small enough you can hot dish them, by putting them in a forge and  
hammering them into a die.

My friend Bernie Hosie, a sculptor over in twisp, builds big spheres  
this way- he cuts geometric shapes out with his plasma cutter, then  
dishes them hot with his 100 ton hydraulic press.

Any way you look at it, forming 1/8" thick steel into spherical  
sections takes a lot of force, hot or cold. The force required goes up  
with the square of the increase in thickness, so 1/8" is 4 times as  
hard to form as 16gage.

You could do it hot, heating small areas with a rosebud, then  
hammering into a depression in the end of  a pipe, or maybe a ring  
made from big round bar. Slow, but it would work. The trick is to move  
each bit the same amount, assuming you want an equal curvature.

Ries




On Feb 23, 2009, at 2:47 PM, Mark Novak wrote:

I'm attempting to bend large, irregular strips of 1/8" mild steel into
a shape suggesting a globe. Any thoughts on method and tools to do
this bending/curving?

Thanks,
Mark
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Ries Niemi
Industrial Artist
http://www.riesniemi.com/