Hello all. I have very limited experience with hydraulic presses and
I recently bought an inexpensive 6 ton one from Harbor Freight. I
have read the posts that state it is worth investing in a good piece
of urethane, but since I am unsure if what I am trying to make will
even work, I wanted to try it out with a piece of rubber first,
before investing $100 in urethane. I am trying to press using pink
rubber-mold sheets and, unfortunately, I am getting no results at
all on my piece of annealed 1.2 mm thick copper. What am I doing
wrong? Any suggestions for urethane substitutes? Also, if I wanted to
invest in the urethane down the road, does anyone know of any
suppliers other than Rio Grande?
It is hard to say what the problem is without knowing more of what
you are trying to do but 1.2 mm thick metal is probably going to
need a lot more pressure than 6 tons for more than very simple
doming. Rubber compresses under pressure and urethane doesn’t so the
rubber will not transfer the energy from the press to the metal very
well where the urethane tends to be much more effective on
transferring energy. No matter where you buy it urethane is not cheap
and most suppliers want you to buy a 12" square piece in any
thickness so even if the cost per square inch is lower the cost per
piece is much higher.
James Binnion @James_Binnion
James Binnion Metal Arts
I am trying to press using pink rubber-mold sheets and,
unfortunately, I am getting no results at all on my piece of
annealed 1.2 mm thick copper. What am I doing wrong? Any
suggestions for urethane substitutes?
I think when I have seen people use rubber they are using layers of
tire inner tube, not mold rubber, which seems much harder than what
you want.
When you buy the urethane, you will need the three different colors,
as sometimes you work the same piece of metal in succession through
he different colors, working your way up to the hardest one.
I am trying to press using pink rubber-mold sheets and,
unfortunately, I am getting no results at all on my piece of
annealed 1.2 mm thick copper. What am I doing wrong?
Urathane works because it does not compress in volume. Like water, it
retains it’s full volume, but can distort, flowing around an
obstruction or intruding object. Other rubbers, because they
compress, don’t offer the support that urathane does. Your pink
rubber may look nice, but you might as well be pressing against wet
clay, for all the support the rubber gives. With urathane, as you
press something down into the rubber, it moves aside, but not
compressing, it needs to then flow up around the object. That’s what
transfers forces back to the sheet forcing it into shape around the
die. Pink rubber just compresses, so no opposing force against the
metal is being exerted. it’s just getting squished down. It needs to
be pushing back against the metal, and a compressable rubber won’t
do that with any appreacable force.
So what you’re doing wrong is simple. You’re using totally the wrong
material, one not capable of what you need. Urathanes are specified
for a reason. They work. Your other options are to create rigid dies
for both male and female shapes. You can do that too, if you wish,
using things like epoxy steel (a mix of epoxy resin and metal powder
that cures to a solid strong rigid mass. It can be cast around a
shape, while contained in a section of pipe. The result is then lubed
with vaseline or other “mold release” and a second cast made of the
first. The result is male and female halves of a die that can press
metal. Urathane is much more versatile though, as it’s universal for
any shape die you might have.
Any tool dealers who carry the Bonny Doon press will carry suitable
urathanes. Since your press is small in capacity, don’t bother
getting large pieces of urathane. I’d suggest you try a small (like 2
or 3 inch) contained block to start (the urathane goes in an open
topped strong steel box, fitted with a matching pushing block. The
urathane goes in first, then the metal, then whatever you’re using as
a forming shape or die, and then the pusher. All this restricts the
flow of the urathane so it can only force the metal up around or into
the die. Makes the press much more efficient than trying to do it
without the containing box.
Megan, possibly the rubber you are using is too thin, or too soft.
Urethane comes is several durometers (hardness), and all of them are
quite firm. You might try a different kind of rubber,or use several
thicknesses.
Also, I use annealed silver usually 28 to 30 gauge—sometimes 26
gauge.
I was very fortunate and got my urethane from a dumpster–yes, a
dumpster. There used to be a factory near Portland that manufactured
the stuff, and several of us went there to purchase some. We were
told that they only sell it wholesale, in huge 6’X6’ sheets or
larger… We looked crestfallen. Then one of the clerks suggested we
look in their dumpster, and we found enough in various durometers for
the 4 of us which they let us have at no charge. The company has
since shut down, so that is no longera source for us.
You might check around in your area and find out if it is being
manufactured there, and perhaps you can get some which might be less
expensive than th at sold by Rio. The stuff is expensive, but it does
the job and cuts down on the frustration of having failures.
A substitute I have used can be obtained in a sporting goods store.
Buy a hockey puck which is made of polyurethane… However I do think
using a heavier jack will give you better results
Megan; The problems you are having are exactly why urathane is used
instead of rubber. urathane has a unique ability to flow under
pressure than return to its original shape that is why it works. I
know of no substitutes. Lee Marshal who owned Bonnie Doon has retired
I think Rio has it now. You might be able to find a urathane supplier
on line. Also if you are learning from scratch I would highly
recommend Susan Kingsley’s book Hydraulic die forming for
metalsmiths.
I always understood that rubber did not compress… soft
rubber may distort much more easily than urethane, but not compress.
Any rubber technicians out there?
You could look for a press owning Orchid member in the area you live
in and ask if they could help you figure oout what is going on.
Designing for the press is different than other fabrication
processes and you need to know the differences. Instead of pissing
money away on bad tools, get the advice first, you may find good
tools cost less in the long run. Also go to the Bonny Doon forum and
ask questions before you spend another dime, I can be contacted off
list for specific questions and so can many other Orchids and BD
forum members.
Please understand that rubber and urethane are very different
materials. There are 1000’s of types of rubber, and 1000’s of
different formulations of urethane. Each formulation is designed for
a specific purpose. The formulation we recommend for hydraulic
forming has properties that allow it to form metals much more
accurately and consistently with better longevity than other ‘stock’
formulations of urethane.
You can buy ‘stock’ grades from MSC (mscdirect.com) or other
suppliers, you will be saving a little money now but it will cost you
more in the long run. “Stock” formulations do not hold up as well and
you’ll be replacing your urethane more often. You will also get
varied results with the pieces that you form with ‘stock’ urethane.
I am still using urethane I bought over 15 years ago. I also know of
a University that purchased a great deal of “stock” urethane which
failed by the end of a one week class.
I would highly recommend that you take a class from a qualified
hydraulic forming instructor. You will gain a vast amount of
knowledge about urethanes and techniques with regards to hydraulic
forming.