I like your second method, but then I'm a blacksmith.

If you're pounding the metal into a hollow, like the pipe, it thins (as
you no doubt noted), leading to punching through. I'd start with thicker
material, maybe 1/8". This method is usually called sinking. You may
also find that a ball pean hammer end is too tight a radius to come out
with a nice finish.

The other way to do this is a little harder, but you don't get punch
through. This method is called raising. You start with a piece of metal
with a diameter equal to the circumference of the finished sphere. You
hammer the metal down over a domed stake or ball, preferably about the
same as your finished piece, but not required. You never hammer so that
the sheet is squished between the hammer and stake (thus thinning it),
you are hammering "on air", bending the sheet down to the form, but not
hitting the form with the hammer. You can start with thinner sheet, say
1/16"; in the end the edges will be thicker. The tricky part is that you
will get wrinkles as you work, which you must get rid of without
thinning the metal.

Someone else suggested copper, which will be a lot easier.

Steve



Vic Barkas wrote:

Hello group,

I am sort of a novice metal sculptor. I work mostly with the
oxy-acetylene torch, some modest blacksmithing equipment, a drill
press, grinder, band saw and the usual small hand and power tools.

My question is, what are some suggestions for making a smallish hollow
steel sphere without my inversting a bunch more in tools, such as a
lathe? I am talking about a sphere the size of a baseball.

Two approiaches I have considered are building it up with rings of
sheet metal, perhaps 1/2 inch wide, and welding them, as like lines of
lingitude on a globe. Pretty tedious. The other method I have
experimented a little with is heating up a 1/16" thick sheet red hot
and pounding it into the open end of a large piece of pipe with the
ball end of a ball pein hammer. I found it somewhat difficult to get
a full hemisphere by this method, and it is also quite possible to
hole the dome with hammer blows. The plan was to create two
hemispheres and weld them together.

Any thoughts? A perfect geometric sphere is not essential.