[TheForge] metal spinning

[Jerry Frost]

Terry:

If you want to make an analog using clay, look to a 
potter's wheel. They not only look like the same 
process is going on, it is in large part the same 
process.

As the tool is passing over the blank the metal is 
usually stretching to conform, however it can and must 
be upset as well to prevent failures.

Rotation speed is determined by a number of variables: 
dia., material, thickness, shape of the finished part, 
type of tooling, (specifically, hand vs. scissor tools) 
personal preference and skill among other lesser 
factors.

Annealing may or may not be necessary depending on many 
of the same factors that determine rotation speed. Pure 
Al is generally easily spun without annealing as long 
as the shape isn't too extreme and the spinner's skill 
level is decent. Most people are taught using Al as 
it's so easily spun. On the other hand the wrong type 
of Al can be a real PITA to spin, most of the AL we 
spun in Father's shop was far FAR from easy to spin. I 
thought SS was easier and most spinners look on SS with 
fear and dread.

My personal favorite is mild steel, it likes to go 
fast, (high rpm) responds well to a sensitive touch and 
almost never fails catastrophically. (read flying 
shrapnel) Brass is a PITA usually requiring multiple 
heat treats unless you're spinning a very simple shape 
or one you can really hog.

Copper is like spinning taffy, requires little force 
and spins really well but work hardens suddenly so you 
have to be on your toes and have a good feel for it. 
Still, copper is good teaching material.

I don't know of any good books that cover the kind of 
spinning we did in Father's shop; we were a production 
shop and used almost exclusively scissor tools. Most 
people spinning manually now use hand tools and I'm 
unfamiliar with the technique. I'll have to ask a 
couple of my old contacts and then get back with the 
name of decent books.

However, on the practical side. Are you thinking of 
trying metal spinning Terry? If so you're not going to 
meet with much if any success, it's VERY phisical and 
if you let it get away from you extremely dangerous. 
Think about a 6-9" diameter metal blank spinning maybe 
3,000 rpm. coming out of the lathe and ripping it's way 
up your arm. A part can also explode if pushed too far 
or hard and the shrapnel can be almost impossible to 
avoid.

I've personally practiced 1st. aid on the aftermath. On 
one occasion it took three of us to apply pressure to 
enough places to control the bleeding. Though nobody 
died in Father's shop a number of guys lost fingers, 
the use there of and in one extreme case his entire 
hand. Dad's insurance paid for LOTS of stitches.

Metal spinning can be very challenging, intensely 
satisfying, hypnotically beautiful to watch and 
cripplingly dangerous. It also takes a number of 
specialty or specially modified machines.

Frosty
-------------------------------
If it ain't forged
it ain't real.
Wrought iron is.
The FrostWorks

Meadow Lakes, AK.


From: "terry l. ridder" <terrylr at blauedonau.com>


> hello;
>
> the other day i happened to be watching the
> discover channel program 'how it's made?'.
> this episode was concerning metal spinning
> pots and pans. at best the information given
> was just a terse overview. the episode did not
> explain metal spinning itself. it is clear that
> a great many things are happening all at once to
> the metal.
>
> the most basic example from the episode was taking
> a large aluminum disc and making a large stock pot.
> the form is a simple straight sided cylinder with
> a flat bottom with a rim at the top. the aluminum
> disc is placed on the bottom of the form and the
> metal spinning lathe is spun up to speed. then using
> a tool which reminded me of a huge roller skate wheel
> the disc was pushed up against the form and into the
> shape of a cylinder. to try and understand what all
> was happening here, i took some plasticine clay and
> made a disc an 1/8 of an inch thick. i then placed
> the disc over a small metal measuring cup. it was 
> clear
> that the disc would have folds and creases if i were
> to attempt to make a clay pot in this manner.
>
> so what is happening with the metal spinning tool and
> the disc? is the disc being drawn out using the tool?
> the episode stated several times that the discs were
> pure aluminum. they did state that the pots and pans
> had to be heat treated during the process because 
> they
> were become hardened by the process.
>
> one thing that was not mentioned in the episode is 
> how
> fast the metal spinning lathe is spinning the metal 
> disc
> that is to be fashioned into a pot or pan. would 
> anyone
> have a rough idea what the rotational speed of the 
> metal
> spinning lathe would be?
>
> are there any good books available that gives a 
> reasonable
> working knowledge of metal spinning? does lindsay 
> books have any books on metal spinning that someone 
> would recommend?
>
> -- 
> terry l. ridder ><>
>