Expanded Metal Orb

[Scott NC]

  I want to make spheres out of expanded metal roughly the size of a softball with very little distortion for a future project, but I am stumped how to do it.  I have 11 gauge or 1/8" in mind.  I have heating cutting and welding capabilities but how to form it into a ball... Any pointers or ideas would be great.  I thought about forming them around a wood ball and burning it out but not very practical or fun...  Thank you very much!  

[George N. M.]

There are a number of ways to form hemispheres and then weld them together.  The commonest commercial process is spinning.  I believe Frosty's father was a metal spinner.  On a blacksmith level you can raise a disk on a stump or swage block which thins the metal at the center.  There is also a method, done on a stake, often used in armor making, which thins the metal on the edge of the original disk.  The first is "sinking," the latter is "raising."  There are also techniques like cutting, dishing, and welding gores of metal together (like the world map projections that sort of look like saw teeth or a peeled orange).

BTW, when you say "expanded metal" do you mean metal that has been split and pulled apart to make diamond shaped holes, like floor plates, or something else?

"By hammer and hand all arts do stand."  

[Scott NC]

  Yes, George I meant stretched expanded metal.  I have a lathe and thought about spinning it.  I have never tried it on sheet metal let alone expanded metal.  I like to try new things though.  When using sinking and raising is it possible to form the top "close to closed"?  In other words how do you get the curveature where it all comes together at the neck/top of it.  If that all makes any sense...    Maybe its impossible without the material getting all crinkled up and distorted.   I dont care if the "diamond shapes" get smaller but don't want wrinkles in the metal itself.   Doing it cold would not work, I think.  Putting sections of curved expanded metal together and tacking them is an option I will think about.  Maybe a good one.  Food for thought.  Tank you.  Scott.

[ThomasPowers]

The easiest is dishing IMNSHPO with an oversized piece of material and then marking and cutting it along a line to make hemispheres. (That way the ugliness gets trimmed off) When done properly you can raise or sink without wrinkles.  I suggest you look at Renaissance armour to see examples of curves done without wrinkles!  You might hunt down an SCA armour maker in your area and see if they can help you.

How big do you want them to be?  Very small and very large both have issues, though different ones.

Now I know they have domed tank ends using a body of water and plastic explosives...

[Scott NC]

  Softball size.  Say 4-5" diameter.  Do you think I should use an oversized charge of plastics due to the loss of pressure because of the diamond shaped holes?  I will study armour.

[ThomasPowers]

I use expanded metal for my coal forge grate, I have a round firepot and so I dish a curve in the expanded metal to sit down in the bottom of the pot where it's cooler. I use a dishing hammer made from a dome headed RR bolt and a dishing form that used to be the bottom of an Oxygen welding tank.  I generally work it cold as it's a shallow dish and soft metal.

(And for the rest of the folks; yes it does burn up on a regular basis, only can run the forge 8 sessions or so before needing another one, but as they are essentially free and do a good job...I had one that when I pulled it had a two inch long stalactite of flux depending from it after  a session of very juicy welds... Generally I pull it before each session and hammer it on the anvil to remove any clinker build up and see what shape it is in.  Got a stack of replacement pieces hanging by the forge so only takes a couple of minutes to swap it out if needed.) 

Spinning expanded metal gives me the willies just thinking of it---I was thinking on how to design a non-catching tool and only thing I could think of was a large diameter ball bearing like 3-4" diameter one for the tip.  Frosty,  as our resident spinnmeister, besides DON'T DO IT!; how would you attempt?

[Frosty]

I wouldn't recommend trying to spin a hemisphere from expanded metal, especially if you aren't a metal spinner! Dad could have probably done it but he's not around. 

It should form easily enough hot, the spaces will just deform to make up for the sections that need to upset. A rounding wooden mallet on a dished wood block or oxy bottle bottom should be easy enough. I pick up old wooden baseball bats to make "shaped" mallets from, somewhere in the shop I have one I turned into a rounding mallet to form dippers and bowls with. I did them from 14ga. hot over my swage block and they went surprisingly fast.

Frosty The Lucky.

[Scott NC]

  What I had in mind was a way to make it out of one piece and have it come out a near perfect sphere ....  I can see now that after reading replies, looking at the cold worked metal forum and thinking about it some more, it's not going to work.  On the bright side I now have an excuse to upgrade to a tig welder and learn a new skill.  I want to make many of them and my old stick welder... well....  As far as spinning them, I may give it a whirl in the future.  I love a challenge.  I'll just stand behind a big piece of plexiglass for the first few.  

[Frosty]

Learn to spin first! Nothing will eat your lunch faster than a metal spinning lathe and there's no way the stresses applied to the blank can be evenly distributed through expanded metal. You'll be lucky if it makes an ugly wad on the tool. If you have to give it a shot you will have to use a scissor tool and large round roller, a drag tool would be like making barbed wire underwear for chances of success.

If you want a relatively invisible seam or single piece hollow sphere perforated sheet is a LOT more civilized to form. Well, it behaves more like solid sheet, Dad used to spin perforated sheet often.

Frosty The Lucky.

[swedefiddle]

Making it from one piece is very difficult. Better to make 2 'Half's'. If you want to make it from one piece, take your baseball and cover it with masking tape. Start to cut the masking tape from a center point, in straight lines to the center point on the other side of the ball (leave the slices attached to the second center). Now lift the slices and  you have a pattern for making a sphere.

Neil

Please do not use all Italic fonts.

Edited January 10, 2021 by Mod30
correct italic font

[JHCC]

One possibility is to make the two haves, tape weld them together, draw the expanded metal pattern on them, and pop them apart. Next, drill, saw, and file the pattern, and then weld the two halves back together.

Here's a great example of some of Ellen Durkan's work using this same kind of piercing technique:

 

[Scott NC]

On 1/9/2021 at 9:04 AM, Frosty said:

Learn to spin first! Nothing will eat your lunch faster than a metal spinning lathe and there's no way the stresses applied to the blank can be evenly distributed through expanded metal. 

  Caution and advice duly noted.  Oddly enough I was watching Focus on Europe on PBS last night and they had a segment on an Italian coppersmith that made cookware.  They showed him spinning a pot.  Kind of mesmerizing to watch.  Barbwire underwear sounds kind of chafey to me.

 

  Neil, thanks for that unique, new to me idea for making a pattern.  One will come in handy as I intend to make many.

 

  Thanks to John.  I will see what works best.  Thats a beautiful work in that video.  I wonder though, where best to display such an item.    Ellen Durkan's work is facinating to say the least!