What's your preferred method for forging circles?

Depending on the size,  3/8ths or smaller,  I'll work it cold through the pritchell or hardy hole until it's close enough to weld, then work it over the face of the anvil to even it out.  Larger stock I'll work hot, weld it and once again work it across the anvil face to get it even.   Usually works really well for me on the bigger circles.  I'm also not working them at high heat and trying to localize to get all the unsightly lumps out.  This is assuming you don't have a roller, bender, or large mandrel. 

 

Kim Thomas pointed out to me this great little hardy tool for larger curves on pages 42-43 of Werk und Werkzeug des Kunstschmieds (The Smithy’s Craft and Tools) by Otto Schmirler:

Here’s my version, welded up from a piece of bent plate and a scrap of angle iron:

It works great.

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Welding over the horn works as well.

My blacksmith master is doing a smaller copy of the "dulle griet" by forging like the original.

They needs lots of rings to size. So welding over the horn and than fitting over mandrel to size.

They have done 40 or so i believe. All from square 20x20 and 25x25.

 

John, thanks for the illustration and pics, looks like a great addition to one's quiver, so to speak.

--Larry

That looks like a simple but effective tool. I will be making that. Thanks.

I start by scarfing the ends on what will be the top and bottom of the ring. Bend the ends over the horn till i have kind of an elongated "C" shape. Heat the middle and close the ring. Then weld the scarfs on the face of the anvil. Spot heat any places that have lumps and bumps and work until round. 

For various reasons, I’ve made more stitch welded circles than forge welded ones. Either way, I pick a spot on the horn with the correct radius, heat the whole ring, and tap wherever there’s air in between. This is probably obvious, but once it’s welded, the radius can’t be too slack anywhere unless it’s too tight somewhere else.  It may take a couple of passes, but once you’ve eliminated the tight spots, you have a perfect circle. 

The same method can be used to true circles that are larger than the maximum diameter of the horn*. Place the circle over the heel of the anvil with the high spot up, and hammer downward. The high spot will come down, and the low areas on either side will bulge out. Just be careful not to overdo it, as there's nothing to keep you from hammering too far down and creating a new low spot. Also, make sure the edges of your anvil aren't too sharp, or you'll damage the inside of the curve.

If you do it right, you can get a very accurate circle very quickly, even working cold (on lighter stock, of course).

*  Or on anvils whose horns don't have circular cross-sections, such as Mouseholes.

I actually have a horn with a (completely) circular cross section and wish I didn’t.  I’m looking for a section on top that matches the inside radius of the ring I’m making. But since the horn is circular, the ring won’t fit on far enough to reach that part until it’s already perfectly round. It’s not terribly hard to work around that (sorry), but an oval cross section would let an imperfect ring clear the body of the horn while still reaching the needed radius on top. 

If you have to make a quantity of them, hot forming around a form is probably the fastest way, especially if you are going to electrically weld the ends together.  The form can be a piece of pipe, an old iron wheel or one you made the hard way over the horn.  I made a tool that in principle is like the one John has shown but is two pieces of round stock welded parallel to a plate with a space between them.  I also have a large chunk of steel that I got from the junk yard that is like a very worn piece of gear and I can work stuff in the valley.  I have used that mostly for forming sheet into cones and such.  I'll get some pictures later this morning once I put my shoes on.   If they are small, bending around a piece of pipe to create a coil spring like thing and then saw/abrasive disc cutting along the length would be quick.  It is how jewelers make jump rings but on a much smaller scale.

Pictures of the tools;

And a construction intended for a sculpture that did not get used.  The cones were formed on the wave type form while the half round part is the bottom of a 20lb propane bottle.