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How to figure stock size to make a bowl?


#1

I want to make some measuring cups on handles from sterling.

I need to know how to figure what size of a plate I need to make a
round bowl that would hold 1/8, 1/4, 1/2, and one cup dry volume and
then weld handles to these.

I am trying to duplicate the idea behind the measuring cups that
Paula Deen uses on her cooking show. The ones she uses are made of
pewter and are made by the Tin Woodsman. A google image search will
show you what I am asking about.

Thanks in advance.


#2
I need to know how to figure what size of a plate I need to make a
round bowl that would hold 1/8, 1/4, 1/2, and one cup dry volume
and then weld handles to these. 

Sometimes simple questions can only be answered with a complicated
answer. I am afraid this is one of such cases.

First step is to select a shape which can later be converted to the
shape required. In most of the case it is hemisphere. Then select
volume required. From volume one must to determine radius of the
hemisphere, and from radius of the hemisphere the radius of the
starting disk can be calculated.

Example:

We want to make a cup with 100 milliliters ( half a cup ) volume.
Volume of a sphere is 4/3 * Pi * r^3. Pi is approximated to 3.14
Since we work with hemisphere our starting volume for calculation is
200 milliliters.

Since 1 milliliter is 1 cubic centimeter, for computational purpose
we will be using 2000 in our formula.

  1. 2000 / 3.14 = 637 which represent 4/3 * r^3

  2. 637 / 4/3 = 478 which represent r^3

  3. take cubic root of the number and radius of the sphere is 7.8 mm.
    which makes diameter of the sphere 14.6 mm.

  4. starting disk diameter is therefore (14.6 * 3.14 * 0.9) / 2
    should be approximated to 21 mm.

Notes:

All results are rounded off upwards.

0.9 is a fudge factor to account for stretching of the metal
technique dependent.

gage of metal is not taken into account since we working with inside
dimensions.

in practice make it slightly larger and when shape is completed
reduce to the required volume.

Leonid Surpin
www.studioarete.com


#3

A good place to start (I would think) would be by measuring around
the diameter of one via the base (height of wall + base + height of
wall) this will give you the circle encompassed by the volume. Now I
know that is going to be way more metal than you really need, but it
is a place to start from.

The rest I’ll leave up to the real silver sheet workers!

Cheers, Thomas Janstrom.
Little Gems.
www.tjlittlegems.com


#4

Correction to the first post.

Instead 2000, 20000 should be used in calculations. (1 cubic
centimeter = 100 cubic millimeters ) which means that all the result
should be adjusted by factor of ten. A good example that all
calculation should be done using calculator.


#5

Functionally it is to draw a side view of the finished bowl. Take
height plus diameter and add them together, and this is the diameter
of the disc you need.

best
Charles


#6
Functionally it is to draw a side view of the finished bowl. Take
height plus diameter and add them together, and this is the
diameter of the disc you need. 

wouldn’t that be diameter + (2x height)? (+ a little extra)


#7

Maybe I’m missing something and am way off base but here goes… I
am reminded of a story about Thomas Edison. The question was “what is
the volume of a light bulb”. Immediately the mathematicians began
their calculations and labored to come up with all the variables of
the curves inherent to a light bulb.

Edison took a light bulb, filled it with water, then poured the
water into a graduated beaker.

The question was regarding the beginning stock required to make a set
of measuring cups. If I wanted to solve this I’d get out my old
friend JettSett [thermosetting plastic]. I’d heat it then mash it
into an existing cup. I now have the volume needed. I can then take
that mass of JettSett, reheat it and form it into any shape I want.
Can create some interesting measuring cup designs. The shapes can be
easily measured with any flexible tape to get the dimensions required
for the sheet stock [taking into consideration adding some extra
"just because"]

Orchid Rules…Karla in Sunny So. California


#8

I have to post a correction to a correction.

It was pointed out to me that I said that 1 cubic centimeter is 100
cubic millimeters. This is patently wrong. 1 cubic centimeter is 1000
cubic millimeters. Sorry if I caused any inconvenience.

Leonid Surpin
www.studioarete.com


#9
The question was regarding the beginning stock required to make a
set of measuring cups. If I wanted to solve this I'd get out my old
friend JettSett [thermosetting plastic]. I'd heat it then mash it
into an existing cup. I now have the volume needed. I can then
take that mass of JettSett, reheat it and form it into any shape I
want. 

This is a very sad commentary on on the state of the Art of working
with metal. Not only Karla did not understand my post, her
alternative is not applicable to the original question.

That aside, I would like to address an aspiring goldsmith. It is
impossible to make any progress without having modest understanding
of simple mathematics, some metallurgy, chemistry, mineralogy, and
few other disciplines. These requirement will never be replaced by
gadget du jour, and no shortcuts exist. So if weaknesses in these
areas present, take steps to remedy them, instead of adopting a
condescending attitude in combination with faux savoir-faire.

Leonid Surpin
www.studioarete.com


#10

I thought this would be a relative easy question to answer. I did
not know I had to be a physist with a degree in applied mathematics
to figure this out :slight_smile:

It was suggested to me to gather several different sized spheres to
simulate the proposed size of the bowl I wanted to create and dip
them in a cylindar of water to displace the amount of liquid I wanted
each bowl to hold. Then transfer that to metal.

It was also suggested to use a cad program, which I don’t have, to
estimate the bowl and get the dimensions needed from the rendering.

The simpilest solution is to buy a set of the measuring cups from
the guy who makes them and just replicate what he did only using
sterling plate instead of pewter.

Short of someone having a better, more simple idea, thats what I
will do.

Thanks


#11
 Maybe I'm missing something and am way off base but here goes.... 

Afraid you did, Karla. The question is what size of sheet metal
(usually a disk) is required to make a bowl or cup of a desired
final size. The answer is not much related to the volume the bowl
will hold, which is what your jet sett tries to solve for. While it
would work to find what other shape of vessel might have the same
holding capacity as the one you’ve molded, it doesn’t give you the
required surface area of the beginning stock you need to start with
to raise the bowl.

Actual calculations of that can get tricky, since in raising, or
metal spinning, the surface area of the sheet can change, variably,
depending on the technique used. The hammering can either stretch the
sheet thinner, or actually cause it to compress on itself, getting
thicker, so a given starting size of disk can actually result in
somewhat of a range of finished vessels, depending on the technique
of the person doing it.

But as Charles already pointed out, the traditional way to estimate
it is simply to take desired maximum height of the vessel and the
desired maximum diameter, and add them together.

Sophie, by the way, wondered whether it shouldn’t be twice the
height plus the diameter. That would be correct for, say, building a
box by scoring and folding sheet metal. But raising simultaneously
stretches and compresses metal. The compression of the outer edge to
a smaller diameter, while stretching it radially at the same time to
keep the same thickness, accounts for why you only add the height
once. You can adjust that starting measurement for differences in
the way you work. For example, you may wish to emphasize the
thickening of the sheet around the edge, so then you might allow
yourself some extra metal. Or if, like me, you are sometimes not as
skilled or careful as you’d like (I do raising only occasionally,
with predictable errors as a result…), and have to deal with
occasional edge cracks or excessive waviness, well, then having a
bit of extra metal you can trim off is useful. But extra metal is
also extra work. It won’t be there to trim off until you’ve gone to
the work of raising it all the way up there in the first place…

Peter


#12
This is a very sad commentary on on the state of the Art of
working with metal. Not only Karla did not understand my post, her
alternative is not applicable to the original question. It is
impossible to make any progress without having modest
understanding of simple mathematics, some metallurgy, chemistry,
mineralogy, and few other disciplines. These requirement will never
be replaced by gadget du jour, and no shortcuts exist. So if
weaknesses in these. areas present, take steps to remedy them,
instead of adopting a. condescending attitude in combination with
faux savoir-faire. Well, Leonid you really let me have it between
the eyes..... 

I did understand [and appreciated] your previous post explaining the
math. I do have an understanding of mathmatics [worked in the
electro mechanical design world]. I was offering a simple way to
obtain the volume of a set of measuring cups. One has to know the
volume to create a container [the raised vessel] to hold that volume.

There was no “condescending attitude in combination with faux
savoir-faire”. I was only offering another path to the goal.

I really don’t understand how the suggestion was any different than
creating a mockup of a proposed project out of card stock. You can
visualize the design and then use segments of the mock up to create
templates for the actual piece.

With the JettSett you obtain the volume of each piece of the
measuring cup set. It can then be remolded to create alternate
shapes while keeping the volume constant. The resulting shape can
then bephysically measured in any direction to help determine the
sheet material required to do the job. If the vessel were to be pear
shape you would quickly see that starting with a disk would result
with excessive metal at one end.

If the project were simple bowl or sphere shapes then calaulations
would be easier. The original post referred to the equipment that
Paula Dean [sp?] uses on her cooking program. Her measuring spoons
are in the shapes of fish. That doesn’t fall into the standard
sphere catagory. I was offering a way to be more creative.

Peter…thank you for your response and the reminder that
metal will moveduring raising and must be accounted for as well as
variation of thickenss.

Orchid Rules…Karla Maxwell in sunny So. Calif