Making a hollow sphere

Look up metal spinning. make 2 hemispheres and then join them.

He said without a lathe!

Lane

This would be a lot easier in copper... Just anneal it, pound it into a sandbag, repeat...

If it is a "one off" and not a production kind of thing, (you didn't say if you wanted to make one or multiple copies) Why reinvent the wheel?

a quick fix would be to get two large ladels from a kitchen supply store, chisle off the handle and weld the two halves together. I just looked in my kitchen and we have one that would hold a baseball, maybe even a softball, but ladels come in different sizes, so just find a size you like and buy two.

If it is essential for you to "make it from scratch" a mold made out of a good chunk of hardwood would be helpful. Take a log round, tall enough to work at a comfortable height, and make a hemisphere hole in the middle of it. You could rough it out with a drill press and finish it up with a hand grinder or chisle. Heat and slowly cool your flat steel blank and then with a ballpeen hammer slowly pound it in, a couple of reheats and slow cooling at stages should keep the metal from tearing. When you have one, make the other and weld away.

Look into hydroforming, might do the trick.

John

what about just using a toilet tank float, does it have to be round?

Go to Ikea, buy two of their stainless steel bowls,join them face-to-face,and weld along the seam. The bottoms are flattened, but a bit of work with a sand bag and a ball faced hammer should take care of that.

McMaster-Carr sells hollow spheres in a variety of sizes, configurations, and materials and will custom make to your order. Search for "float balls" on their web site:

YOu can dish steel sheet to a sphere, and then use raising techniques over a stake to take it to almost a complete sphere, if having an opening is ok. All you need are hammers and a ball stake.

What you describe below is dishing, but you don't need to do it hot (it does make it easier.) Using hammers with a face radius similar to the final result you want will make it easier.

Since two hemispheres are ok. get to the point where you have dished it close, and then put it over a ball of some sort, and start planishing it closer to your final shape.

jk

"Vic Barkas" wrote: (clip) heating up a 1/16" thick sheet red hot and pounding it into the open end of a large piece of pipe(clip) ^^^^^^^^^^^^^^^ Pounding into a hole , like the end of a pipe won't work too well, as you have discovered. However, if you hear a circular piece of steel red hot, you can pound it on an anvil into a cup shape. If you have difficulty making the cup deep enough, take a V-shaped dart out, close it up, weld it and pound some more. After you have a few of these, you can assemble and weld them into a sort of sphere, and grind smooth.

You did say you have plenty of time, didn't you?

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:

Deja vu all over again!

or...

"Two minds without a single thought." *

I did exactly that about 45 years ago when I needed a perforated stainless sphere to make the outer grid of an ion density measuring probe for use on a high altitude sounding rocket.

In those pre NC daze some poor sod in the model shop had to hand crank an index head forever to drill longitudinal lines of holes through the two ladle bowls.

See:

More silly stuff from me relating to that era is at:

Jeff

• Not meant to be insulting, it's an old reference to Laurel and Hardsy....

That kind of depends on the goal - making the spheres or the thing they go on/in .

Contact Kent White and ask him.

Lane

king architectural metals has balls and hemispheres ranging in diameter from like about 1 1/2" to 12", i think they have better prices than mcmaster/carr.

(they're pretty nice, they'll send you a hard copy catalog for free. the hard copy version is much nicer to leaf through.) (ernie mentioned king architectural metals here on this list a while ago, thanks ernie)

b.w.

(i couldn't resist an opportunity to post pics of the project to the dropbox) spheres_steel.txt spheres_steel_rock.jpg

oops...

Just for reference, the 4th of July weekend Woodwright's Shop (PBS) had a gal in that was doing metalsmithing. Made up a teapot on the show. The techniques for making hemispheeres would just be an extension of work on these techniques. The two top pieces were well domed and she was working with tinned steel.

-- Why isn't there an Ozone Hole at the NORTH Pole?

I would raise it, as Steve described. I might start with tuck shrinking, which is a sheet metal technique used by metalshapers, but ultimately I would be raising.

My local bearing supply house sells individual solid steel balls, as does McMaster Carr. Buy one 2 inches in diameter or so, weld or otherwise fasten it to something that you can clamp into a vise. At that point you have a ball stake or post dolly, which will be very helpful in making a hemisphere. You do not need anything other than a hammer and a ball stake to make a hemisphere. The link below shows, among other things, a ball stake, in the photo with the sheet metal stakes.

I sometimes make bowls, but have never made a hemisphere. Maybe I will try to make one sometime soon.

Richard http://www.fergus> I like your second method, but then I'm a blacksmith.