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Scaled down pancake dies


#1

Since pancake die technology was scaled way down for jewelry, from
it’s original use of cutting airplane wing parts, it obviously scales
back up again. What is not common knowledge is the exact
proportions/dimensions of those very large dies, and we don’t even
need to know, for jewelry purposes, and decorative metal art uses. I
know of a couple folks besides myself who have had large dies cut by
the wire edm process, but I don’t have specs on hand, so it looks
like you’re stuck with me and my projects, as far as that goes.

On the jewelry scale, one main consideration is to not use thicker
steel than is required for the thickness of the metal to be cut,
because hand-sawn dies are difficult enough using the thinnest steel
needed, we don’t want to make life harder unless we need to, as in
the cases of intricate designs, or for tough metals, and sometimes
very-thin metals. Yes, that’s correct, I often use 1/16" steel
instead of 3/64" for 28 ga. and thinner materials because the
decreased angle on the cutting edge of the die just works better,
allowing for dies that start out tighter and stay tighter with use.
Very-thin metals ask for very-tight dies, and also, thinner steel can
allow for a tiny bit of flex in the die and this is something that
can cause problems.

With edm-cut dies, we are able to use thicker steel, and so keep the
larger dies proportionally similar to the smaller ones, since the
physical difficulty of cutting thick steel is eliminated by the edm.
For reasons too extensive and varied to cover fully in this post, I
won’t go far into why the range of die sizes does not need to be
proportionally exact as sizes go up and down, so ‘proportionally
similar’ will do, as it does in practice. Similar design-to-hinge
ratio, similar overall size-to-thickness ratio, and the range of
ratios used is rather wide too. I never use ratios when planning
dies; I just go by look, and ‘feel’. As I go up in size within my
normal range , I run out of room for hinge length, and so in those
cases hinges are shorter in relation to design size, which
functionally forces me to sometimes use thinner steel than I want,
as too-short-hinge plus extra-thick-steel equals a die that is too
hard to open (though that can be dealt with by heat-positioning
heat-treated dies) and potentially has to open and close so far that
it may fatigue the hinge.

With oversize dies that are edm cut, assuming kiln size is not a
limiting factor (which it often is !) we have more freedom to expand
the hinge length, and go up in thickness as called for, but this
quickly increases die weight, and soon that becomes prohibitive for
normal use by hand loading dies in production. The largest die I
made was about 12" by 30" and cut (and formed) a leaf about 9" tall
and wide (see ‘giant leaf die’ or similar thread on the old Bonny
Doon archives from several years ago, it may still be there). I used
1/8" steel and the die came out a little on the flimsy side
(proportionally large compared to it’s thickness)but was still so
heavy that I spent hours drilling holes all over it to remove
material and decrease weight. Here’s where it gets interesting :
compared to a ‘normal’ die, about 4" long, cutting a 3/4" circle,
using 1/16" steel, this die was VERY thin compared to it’s size. In
fact, to make it the same proportionally, it would have to be made of
steel about 7/8" thick. It’s obvious that this would be too heavy to
be practical, and there’s no way the hinge would function the same
as a smaller die. Using 1/4" steel for that big leaf would have been
a good functional compromise, but still would have made for a very,
very heavy die.

One customer also had me make several dies in the 8" by 6" range,
with resulting die plates around 12" by 12", and the 1/8" steel was
just about right for these. Thick enough to still be stiff --not so
thin proportionally as the giant one,the flexibility and flimsiness
in proportionally thin dies mentioned earlier can allow thin metal
to become jammed in the die, which is bad (obviously) and can ruin
the cutting edges–, and small enough to be physically more
manageable, and openable.

This all brings us in a round about way to a die I just made that
was forcutting a 3" circle in 3mmm thick (very close to 1/8" )
material. 3/16" steel would have been fine, leaving 1/16" of
’headroom’ between die and material thickness, but I bought a piece
of 1/4" steel for the job. This was a good choice to give the die
extra beef for a tough job cutting gold and palladium mokume, but
only 6" of hinge for a 3" circle, in 1/4" steel is right on the edge
of what’s going to open and close well. It was hard to prop it open
to do the heat-positioning step, and hard to open it enough to put
in the piece of 3/16" thick aluminum test-piece that I used.

This die weighs about 4 pounds and it took about 20 tons to cut
3/16" thicl Al.

I’ve uploaded a shot of this 3" circle die to my photobucket site

and feel free to browse the excessively cute chihuahua shots, and
the beautiful area of Rio Grande bosque forest/marsh where we’re at
now, and otherassorted metal objects.

Dar Shelton
SHELTECH
www.sheltech.net


#2

Amendment:

After re-doing the math, and doing some more, I came up with a
general formula that works for dies of various sizes and thicknesses.
I mis-stated that the 30" long die would need to be 7/8" thick to be
proportionally the same as the 1/16" thick, 4" long die. The correct
figure for the big die thickness is about 1/2", which is NOT to say
that it should be made of 1/2" steel, just that if it were, it would
be the same proportionally as the 1/16" die. Those proportions are
thickness times 64 equals overall length of die. That’s for cutting
about a 3/4" circle on the small die, and about a 5" circle on the
30" die. This gives overall design, thickness, hinge-length, and
overall-length proportions similar in both dies. Correlating this
ratio to other thicknesses of steel, we end up with die sizes and
thicknesses in general alignment with what I use in practice. The
1/4" die , 11" by 5", would be 3/16" thick according to this
’formula’, and that’s what I stated as would be good at first. It
could be thinner, 1/8" or even 3/32", or even thinner, 1/16" and work
for most applications, and this is in fact what I use whenever I feel
like I can get away with it, because, while 1/16" is no picnic to
saw, the thicker steels become extremely taxing physically to saw. I
have not yet set up my powered saw from Lee Marshall, but that whole
subject will come later. The formula gives a die length of 5" for
5/64" steel, 6" for 3/32" steel, and 3" for 3/64" steel, though as
stated, nothing is a set rule here, just general guidelines ; the
range of what works outside the guidelines is generous and
forgiving… to a point. Hinge length and therefore overall length
should be increased as design size goes up, especially when thickness
goes up. Lots of details I’m leaving out for the sake of simplicity
right now.

Dar
www.sheltech.net