I bought the metal spinning CD from James Riser and the two DVD set
from Terry Tynan. But nowhere was it mentioned how to determine what
size to make the starting disc. Or, if it was, I keep missing it.
Anybody have any info on this?
Thanks,
Eric R Snow

As I understand the process, you would take a flexible tape measure from
one lip of the shape to the other lip, going across the bottom. (You
could do this off a drawing of the cross section as well). The
shrinking occurs in the other axis (circumferential axis), but this
dimension should not change much during the spinning process. Then add
something to the diameter, maybe 1/2 inch, which will be cut off after
the shape is completely spun. Ultimately you will tune this dimension
through trial and error, after you have spun a piece or two using the form.

I admit that I am talking theoretically, but I have been working on
forming sheet metal using other techniques for some time, and have a
good understanding of what is happening when you stretch or shrink sheet
metal.

Richard


Eric R Snow wrote:

I bought the metal spinning CD from James Riser and the two DVD set
from Terry Tynan. But nowhere was it mentioned how to determine what
size to make the starting disc. Or, if it was, I keep missing it.
Anybody have any info on this?
Thanks,
Eric R Snow

Eric, first a thank you for buying the DVD. Asking what size to cut
a circle for any given shape to be spun, is really an no more than an
educated guess, it depends on the type of material to be used then the
gauge, shape of the spinning, the spinning tool you will use to spin
the part, etc the list goes on. A spinner will just take an educated
guess from previous jobs he has worked on, spin the part down and if he
finds it to be too small he will stretch the material to size as long
as the tolerance allows, if it is too big he will simply trim off the
extra material. If he removes an =BC" by trimming he will make the
circle size =BC" smaller, or visa versa then cut all the blanks
required to spin the job.

Hope this helps

Terry Tynan






Eric R Snow wrote:
I bought the metal spinning CD from James Riser and the two DVD set
from Terry Tynan. But nowhere was it mentioned how to determine what
size to make the starting disc. Or, if it was, I keep missing it.
Anybody have any info on this?
Thanks,
Eric R Snow

On 4 May 2005 17:04:34 -0700, "Terry" wrote:


Eric, first a thank you for buying the DVD. Asking what size to cut
a circle for any given shape to be spun, is really an no more than an
educated guess, it depends on the type of material to be used then the
gauge, shape of the spinning, the spinning tool you will use to spin
the part, etc the list goes on. A spinner will just take an educated
guess from previous jobs he has worked on, spin the part down and if he
finds it to be too small he will stretch the material to size as long
as the tolerance allows, if it is too big he will simply trim off the
extra material. If he removes an ¼" by trimming he will make the
circle size ¼" smaller, or visa versa then cut all the blanks
required to spin the job.

Hope this helps

Terry Tynan






Eric R Snow wrote:
I bought the metal spinning CD from James Riser and the two DVD set
from Terry Tynan. But nowhere was it mentioned how to determine what
size to make the starting disc. Or, if it was, I keep missing it.
Anybody have any info on this?
Thanks,
Eric R Snow
It helps some. I did spin my first part using the proper too a couple
days ago. Though small, it came out nice. I'll post pictures in the
drop box later.
ERS

A easy way to get close to the size simply add the height and then the
diameter. For instance if you wanted a 6 inch high vessle and the
diameter is 3 inches than you would need a 9 inch disc. If the sides
taper or the base is rounded than you could go a little smaller.
Better to have enough material than coming up too small.

Eric R Snow wrote:
On 4 May 2005 17:04:34 -0700, "Terry" wrote:


Eric, first a thank you for buying the DVD. Asking what size to
cut
a circle for any given shape to be spun, is really an no more than
an
educated guess, it depends on the type of material to be used then
the
gauge, shape of the spinning, the spinning tool you will use to spin
the part, etc the list goes on. A spinner will just take an educated
guess from previous jobs he has worked on, spin the part down and if
he
finds it to be too small he will stretch the material to size as
long
as the tolerance allows, if it is too big he will simply trim off
the
extra material. If he removes an =BC" by trimming he will make the
circle size =BC" smaller, or visa versa then cut all the blanks
required to spin the job.

Hope this helps

Terry Tynan






Eric R Snow wrote:
I bought the metal spinning CD from James Riser and the two DVD
set
from Terry Tynan. But nowhere was it mentioned how to determine
what
size to make the starting disc. Or, if it was, I keep missing it.
Anybody have any info on this?
Thanks,
Eric R Snow
It helps some. I did spin my first part using the proper too a couple
days ago. Though small, it came out nice. I'll post pictures in the
drop box later.
ERS

On 6 May 2005 07:04:03 -0700, "warren"
wrote:

A easy way to get close to the size simply add the height and then the
diameter. For instance if you wanted a 6 inch high vessle and the
diameter is 3 inches than you would need a 9 inch disc. If the sides
taper or the base is rounded than you could go a little smaller.
Better to have enough material than coming up too small.

I would be surprised if the disk would stretch that much. I would
start with a little less than twice the height plus the base diameter.
Gerry :-)}
London, Canada

Gerald, I do hollowware in sterling silver and copper by raising with a
hammer. There is not any stretch to the metal. You are just moving the
metal. Or raising it upward (to the opening). Same thing applies to
spinning you are raising the metal upward. This formula has been around
for centuries. If you used your formula then you would need a disc 15
inches in diameter and one heck of a big lathe.


Gerald Miller wrote:
On 6 May 2005 07:04:03 -0700, "warren"
wrote:

A easy way to get close to the size simply add the height and then
the
diameter. For instance if you wanted a 6 inch high vessle and the
diameter is 3 inches than you would need a 9 inch disc. If the sides
taper or the base is rounded than you could go a little smaller.
Better to have enough material than coming up too small.

I would be surprised if the disk would stretch that much. I would
start with a little less than twice the height plus the base
diameter.
Gerry :-)}
London, Canada