[TheForge] Bending steel

[Bob Ehrenberger]

Mark,

I make 18" bowls out of 16ga steel.  Which is about half what you are 
looking to do.  The first one took over 5 hours and about killed me, but now 
I can do one in under an hour.

My method is a bit crude but effective.  I use a truck tire rim as a sinking 
form.  I get the steel hot in the forge lay it over the rim and wale at it 
with a slege hammer until it starts to develope wrinkles. I then take it to 
the swage block and hammer out the wrinkles with a rounding hammer. I get it 
hot and repeat until it gets deep enough to where the handle on the sledge 
hits the rim of the bowl, at that point I switch to a heavy sinking hammer 
that will reach into the deep bowl. The deeper the bowl gets the less it 
tends to wrinkle.

For something as big as you want, you may need to make a sinking hammer out 
of one of those spike driving hammers you see at flea markets every now and 
then.  It would have the weight and the reach needed for a big bowl/sphere.

PS: My portable forge is made from the end of a large LP tank which is a 2' 
diamiter sphere. It would make a nice form if you can find one.

Robert Ehrenberger
Shelbyville, Mo.
eforge at centurytel.net

Date: Mon, 23 Feb 2009 17:34:33 -0800
From: Mark Novak <mark at fireworkspdx.com>
Subject: Re: [TheForge] Bending steel

I'm planning on cutting 1/8" sheet into irregular strips, likely 4-5"
at widest, and then bending them and making them convex enough to
ultimately come to a 3-4' sphere (though it will not be a complete
sphere - there will be intentional gaps so that the object suspended
in the middle of the sphere will be plainly visible).

I'm considering making a jig (like the large bowl of my swage block)
that I can hammer it into hot, though I know there will be dents and
distortion without some uniform press die... I'm hoping what ends up
visible from the outside will either grind out or be attractive. :)

Since I have a tiny shop without any power hammers or presses, I'm
hoping I can accomplish this with hand power or some jury-rigged press
(thoughts on that?).  Thanks for your advice! Keep it coming, please.

Mark