Forging large curves

[IanR]

I have just finished making a new firescreen for our open fire, which has a arched opening. I made the frames of the screens (two hinged halves) to match the opening by forging the curve on the horn of the anvil, using 32mmx5mm flat bar. This was a fairly difficult task, is there a easier or better way to make large curves that flow nicely? I haven't got a photo but I can take one tomorrow if anyone wants to see it.

[Glenn]

Make up a jig smaller than the actual curve to allow for spring back. Clamp one end and bend the curve longer than needed so you can then cut to length. This can be done cold by hand, or with the aid of a bending fork (or two).

[Charlotte]

When I've been faced with this problem in the past the way I've done it, on the edge, or on the flat, is to open my biggest vice to an opening that is one half and inch to one inch,( about 13 mm, to 25 mm ) larger than the dimension that I'm bending, in this case the width 35 mm ( approx 1 1/4) , or the thickness, 5mm (approx 3/16,) I clamp the vice closed tightly on two spacers placed to prevent twist or bending a helix unintentionaly.

Taking a piece of steel much longer than the circumference, of the circle I'm bending and allowing 5-6 inches (100-120mm) to project beyond the bottom of the vice jaws I begin to "bump" a bend into the curve along the direction I want. If I want a taper I forge that before the bend. If I'm doing a pair I work them alternately trying to keep them the same shape as much as possible


You will be surprised that the amount of stretching you can do to the outside of the curve compared to the inside compression done cold. The centerline of the curve tends to be rather closer to the inside that the outside. If I need to make a hot bend, for a really tight radius on tough material, I make curved jaw spacers from heavy weight angle of appropriate size and curve to prevent more edge upset than necessary that needs to be forged smooth.

[John B]

This is where a flypress is handy for hot or cold curves on flat or edge.

Otherwise if you dont have one, two pairs of large scrolling wrenches One located fixed in a vice, the other used to pull the material towards you and work supports at either side to keep workpiece flat and level.

Ensure wrenches have large radius on jaws as they can mark the workpiece if you ae doing it cold, but then again you can feature that as a textured finish. (As has been said before, "If it's a cock up, feature it")

[IanR]

A big thanks to everyone for your answers and images,we have another similar fireplace, so sometime in the future I will be making another one. I will be able to put your ideas into practice for that and also any other projects requiring the same.

Thanks again
Ian Ross

[irnsrgn]

If bending the Hard way on edge, use a Cheese Fuller or the round face of a farriers turning hammer and a small section of pipe in the hardy hole of your anvil and gradually work the bend.



Or if the Easy way on the flat, tack weld a short section of flat strap with the desired curve and a stop piece,



and just pull it around carefully using a bending fork if necessary to help.

[IanR]

Irnsrgn, thanks for your answers and great photos, gives me an idea for a hammer for when I attempt to make one.