[TheForge] metal spinning

[Jerry Frost]

I have a clue but not the knowledge of specifically 
what's happening but thanks. <grin>

Pretty similar to angle raising if you think of it as 
one long progerssive impact. No upsetting in a shear 
spun cylinder, all stretch.

Spun with a scissor tool in multiple passes is a 
different thing all together. The spinner will form the 
blank down over the die moving from the center to the 
outside edge of the blank, moving the metal against the 
die as far as possible, then moving to the outer edge 
to maintain the shape and position of the blank. On the 
return the spinner brings the tool back from the outer 
edge to the die and at this time is upsetting to 
maintain the proper thickness.

Multiple pass spinning even with scissor tooling is 
much more skill intense than shear spinning. Hand 
spinning is WAY more difficult as the contact point 
between the tool is sliding over the blank rather than 
rolling like a scissor or automatic machine tool. Hand 
spinning is far and away harder to do, longer to learn 
and more dangerous.

The "sweet spot" is a combination of the right rotation 
speed for the blank dia., thickness and material 
coupled with the right roller dia, tool position, 
pressure and pass speed. Spinning in the sweet spot the 
metal does what you ask it to rather than being forced 
into submission by main strength. Mild steel has a 
closey defined but vivid sweet spot, it's easy to find 
and easy to keep. Soft, pure or low alloy aluminum has 
a wide semi-sweet zone you kind of mush into and roll 
through.

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

Meadow Lakes, AK.


From: "Peter Hirst" <saltydog335 at aol.com>


> 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
>
>