How to make a near perfect circle

[ichudov]

Need some practical ideas. I want to decorate my mailbox so that it looks like a steam locomotive. Mailbox is shown here

Mailbox

To that end, I need to make 8-10 round "wheels", which I would like to forge from a steel bar. I would say between 3 and 5 inch diameter. So they do not have to be strong, or even continuous (I cannot forge weld) but they have to be of uniform size and round. I could TIG weld afterwards.

I would also make spokes by means of TIG, so it is not a problem.

My main question is how to make circles from steel bar.

[arftist]

Find something with the outside diameter the same as the inside diameter of the circle you want. Wrap your steel bar around it to form a coil, whether it overlaps by a little or many turns. Cut off each wrap or coil, flatten and weld the seam.

[bigfootnampa]

Do it like we make jump rings... wrap a mandrel (steel pipe or tube) and cut with a cut-off wheel. I think it would be easier to hard solder than to weld them. You'll likely have to wrap hot with a torch.

[matt87]

What stock do you want to make them from -- circle, oval, triangle, square, diamond, rectangle? If rectangular section, do you want to bend them around the narrow or wide dimension? If the wide dimension I suggest you watch Mark Aspery's YouTube video where he teaches 'shop math' on how to calculate the length of steel for such an endeavor.

I'd say forge as well as you can freehand, weld, then true over a cone mandrel. Of course for me step 1 would be 'make a cone mandrel'... You may have luck truing by eye on the anvil.

You may consider it cheating, but do you have a suitable piece of pipe and a saw? Many rings of any thickness you want there! :D

[Rich Hale]

Cut off ends from pipe the right size

[Glenn]

Why not just cut sections from a 3 to 5 inch pipe the width of the wheel?

[ichudov]

Why not just cut sections from a 3 to 5 inch pipe the width of the wheel?

To be realistic, it would need to be thicker than a water pipe.

[Old South Creations]

find a piece of pipe, etc the right outside diameter and form it around that...that's what I do when I need something like that. Put the pipe in a vise, get your stock hot, use a pair of pliers to "clamp" the stock to the pipe, and simply wrap the stock around the pipe

[olcarguy]

Pipe is available in many wall thicknesses, fron thin wall to 1" and thicker. It all depends on the presure the pipe was designed to hold. Go to your local scrappy and start looking....

[Ten Hammers]

figure your wanted outside diameter. Figure the thickness of the wheel rim you wish. Figure the inside diameter of the wheel. Match that with pipe or forge a fixture to match that diameter (if you need 4 5/8 fixture od and have 4" then wrap 5/16 bar over that and get the dimension you need). this done with pipe, starting the rings on the pipe with vise grip clamp and either walk around with channellocks or standard pliers. Use longer piece to wrap. Over wrap and saw (hot) in chopsaw to leave fillet to fill with MIG (or your choice). I might add that you can straighten this back out to get a measurement for other wheels or give yourself a witness mark on the stock before making the ring to get a place to measure. Should be able to get a circumference length fairly easily. Make a practice second piece using this length. All good, then cut the rest to length. Thicker than standard pipe to me will mean 1/4 to 3/8 thick bar needed. as noted you can find some schedule 80 pipe or more OR use method I have described and wrap bar stock. you will need lot of heat and a strong fixture welded to a piece of angle to go in a strong vise or clamped well to a table. With 3/8 you may need to start the ring in a fork or vise jaw to get the wrap started and clamped. the hotter the better on the stock. I have experience in deals like this and it is a lot of work but the ends justify the means if you plan correctly. you WILL use a lot of energy to forge rings in this method. Wrapping rod or square to make rings and then sawing is another matter. I assume you want bar stock that is 3/4 to 1" wide for this. This rascal will be a heavy thing if so. You can also wrap 3/4 wide stock( say 3/16 thick) the hard way to get the needed mass look if you wish. 1/8 x 1/2 wraps nicely the hard way too. would be much lighter and THIS could be coil wrapped (kinda tough) and sawed. The other alternative is find an industrial supply and buy washers of this size. Ironworker slugs also come into play. Have fun.

[David Einhorn]

If you have access to a floor mandrel the simplest method would be:
1) Cut the number of lengths of iron to the same length
2) Roughly forge the each length into a circle on the anvil.
3) Weld ends together
4) Heat up each ring one at a time and drop over the top of the mandrel.
5) Wherever you see light between the iron and the mandrel, tap with a hammer.

alternate step 5: if you don't have a floor mandrel, then true up each ring on the horn of an anvil.