[TheForge] metal spinning

[Peter Hirst]

For a guy with no clue what he was doing, Frosty, you did an absoulutely 
masterful - even poetic -- job of conveyng its essence.  Reall, nicely done.

Then we have:

" it seems
to me that if you take a disk and force the sides up ,by spinning
to make a pot,,,,that the sides must upset or thicken
progressively as they conform to the spinning form.
That would be the case if one were angle raising the vessel"

Makes sense as far as it goes, but if the vertical side of the finished pot 
measured more - say twice as much - as the difference between the radius of 
the bottom and the radius of the startng disk, then there would not 
necessarily be as  much - or at some point  any -  net thickening of the 
material.  Isn't that  the case in angle raising,  simultaneously peening? 
It seems that this may be what Frosty describes as hitting the "sweet spot", 
perhaps a point at which the planar shape changes but the drawing and 
upsetting are exactly balanced.

Hay, this is fun, isn't it?  Trying to describe these things without 
drawings?  Kinda like describing a tomato without using your hands.


Keziah







----- Original Message ----- 
From: "Peter Fels And Phoebe Palmer" <artgawk at thegrid.net>
To: "terry l. ridder" <terrylr at blauedonau.com>; "Sponsored by ABANA" 
<theforge at mailman.qth.net>
Sent: Tuesday, February 26, 2008 2:55 AM
Subject: Re: [TheForge] metal spinning


> Terry:
> Perhaps i don't understand just what your are doing, but it seems to me 
> that if you take a disk and force the sides up ,by spinning to make a 
> pot,,,,that the sides must upset or thicken progressively as they conform 
> to the spinning form.
> That would be the case if one were angle raising the vessel...pf
>
> terry l. ridder wrote:
>> hello frosty;
>>
>> thank you for the reply. i seriously
>> doubt that i would have the physical
>> stamina for metal spinning. i would
>> like to have a better understanding of
>> what is happening to the metal, by
>> what, and how. also to have contacts with
>> metal spinners in case i would need to refer
>> someone to one.
>>
>> it appears that the metal is being deformed
>> , stretched in one location and compressed in
>> another location. given the starting shape of
>> a metal circular disk and the ending shape for
>> example a simple right circular cylinder. a
>> stock pot. there is some serious plastic
>> deformation occurring but i am not understanding
>> where and how. that is what i would like to
>> understand.
>>
>> On Mon, 25 Feb 2008, Jerry Frost wrote:
>>
>>> 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
>>>
>>
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