[TheForge] 36" diameter ring

[theforge@mailman.qth.net]

There are several ways to figure it mathmatically, several people have 
already responded with those methods, complete with bend allowance.   If 
you have the kettle, nothing beats trial fitting to the actual object, 
and then marking it.  In that case, you wouldn't weld the ends until the 
very end.   Cutting it in advance to an exact length is not likely to 
give you as tight a fit since the operations you undertake to shape it 
will stretch the metal some (why else would it curve).  Forge welding 
will make it even more difficult to figure the end diameter.  Further, 
if the kettle is not perfectly round, it will further frustrate you 
efforts.  For something  large I usually multiply 3.14 x diameter 
desired then add several inches and cut to length after I have it 
shaped.     Even on small things, I will do the same.  I made several 
dozen stands and hangers to hold clay pots last year for a friend with a 
garden center.  The rings had to catch the upper lip of the pot, which 
was only 1/8" to  1/4" step, so it had to fit pretty tight.    The 
secret to getting it round is patience and not trying to do it in one 
pass, regardless of wether you use a bending jig, forks or a bender.  I 
have a ring roller as well, andsleak up on the diameter with that one 
too.   It is much easier to increase the curve with another tap, than to 
take the curve out.  You only want to put a barely perceptable bend in 
the metal each time as you work your way around.  After a couple of 
passes you will have a good feel for how agressive you can be.    If you 
start to form a helix, you can take it out with careful bending, or you 
can peen the metal on the inside curve of the helix till it straightens. 

Charles

Bob Rackers wrote:

>I know figuring the length is a little more complicated than that.
>I have a carriage-maker friend who makes tires all the time, and he gave me the
>calculation he uses, but of course, I've forgotten it.
>I'll post it when I get it from him again.
>
>Bob
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