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Hydraulic press


Hi everyone,

I have been quietly gleaning knowledge for quite some time now
and am really grateful to everyone responsible for this forum and
for all the that is shared. I have a question that I
would appreciate some help with.

I am considering purchasing a new hydraulic press, but the two I
saw have rough surfaces around the top part of the ram part way
down from the top and a few nicks that can be seen and felt with
my fingernail. My understanding has always been that the ram
should have a smooth polished surface. Question : Will this
eventually cause damage to the seal and make it leak. The
seller claims that the finish on the ram won’t make a difference
if it is smooth or rough or even threaded.

Any advice would be greatly appreciated. I wouldn’t want to be
stuck with a leaking press after the 1 year warranty expires.



Are you talking about the jack itself, not the press? Where are
you buying this? A car jack won’t due. You could buy it from or look locally for a source, though I
looked into it and you can save little to nothing buy buying from
a local jack source. Do you have a press already?




A 20-ton “car” jack (aka “bottle” jack) is the same jack that
Bonny Doone sells. The difference is that Lee Marshall installs
(for an extra charge) a gauge. The gauge isn’t absolutely
necessary, but it sure makes hydraulic die forming a lot more
efficient and enjoyable. Can’t really know how much psi is being
applied by any other method.

For detailed info on hydraulic presses (including how to build
your own), power sources for the press (there are others besides
the 20-ton bottle jack), and safety considerations regarding the
use of these tools, read Susan Kingsley’s book “Die Forming for
Jewelers & Metalsmiths”. Available from 20-Ton Press, P.O. Box
222492, Carmel, CA 93922. Or check out Borders Book suppliers
Webb site.

P.S. Getting back to the original question, will nicks on the
ram damage the seal? I’d like to see an answer from someone
knowledgeable on this matter.



A 20-ton “car” jack (aka “bottle” jack) is the same jack that
Bonny Doone sells. The difference is that Lee Marshall installs
(for an extra charge) a gauge.

According to Lee, the last time I talked to him, he makes
several other internal modification to the jack that give it
improved performance and longevity in these presses. Don’t know
if it was just a sales pitch, but I trust him to have been
telling me the truth, especially since he already had my
commitment to buy a press…

Peter Rowe

  A 20-ton "car" jack (aka "bottle" jack) is the same jack
that Bonny Doone sells. 

As with all products, there is a wide range of quality. The
common car jack is the wrong size for most presses and poorly
made. The common 20 ton car jack that is sold at my local car
parts store for $50.00 is most definitely not the same one
Bonny Doone sells for $95. to $250. (or so).

There is a whole class of jacks that are higher quality – one
can buy these from Lee Marshall or locally. I am aware of what
Lee Marshall does to the jacks he buys from Taiwan or wherever.
He adds to “T” attachment, the gauge, cuts off a corner of the
base, and paints them.

I investigated the matter locally and found I could buy a
similar jack (without gauge) for less. Some of these jacks had
the port for the gauge, so that I could add it myself. But then
I would have had to install the gauge, and still wouldn’t have
had the “T” attachment.



Hi Carol,

P.S. Getting back to the original question, will nicks on the
ram damage the seal? I'd like to see an answer from someone
knowledgeable on this matter.

Every hydraulic cylinder has a seal at it’s working end (the end
where the piston or ram extends from them cylinder). The purpose
of the seal is to prevent the fluid used in the cylinder from
leaking. The piston or ram usually has some type of mechanism at
its lower end (rings similar to those used in internal
combustion engines or some solid material that is a very tight or
interference fit with the walls of the cylinder) to prevent the
hydraulic fluid from being forced past them & escaping. The seal
at the top end of the cylinder may be similar or it may be made
of weaker material. It’s design is dependent on the size &
amount of pressure the assembly will be subjected to.

Any nick or discontinuity in the ram where it passes through the
seal has the potential to cause a leak. If the damaged part of
the ram has rough edges, they are apt to abrade the seal where
contacted. An abraded seal will no longer contact the ram with
the same pressure in all areas, thus a leak can develop in the
areas of less contact.

Without seeing the cylinder & ram in question, it’s hard to
define the potential for a leak based on a description. However,
if the nick or blemish is on any part of the ram that passes
through a seal, it can damage the seal & may cause a leak.

The rams used in some hydraulic cylinders are longer than the
cylinder & the top portion of them never enters the cylinder. If
this is the case, any nicks or blemishes to the ram above the
cylinder when all pressure is removed from the system will not
cause a leak.



Elaine, Sorry for the confusing statements. I should have said
something more like "the 20-ton “bottle” jack is the same one
that Lee Marshall rebuilds, modifies and improves before
re-selling it. While this makes it a better tool for die forming
with the hydraulic press, it is still a “bottle” jack. Harbor
Freight sells one for $45 dollars and outwardly it looks exactly
like what Lee sells (minus the paint and the gauge). It is inside
where the greatest improvements are made. You’re right, it may
look the same, but it isn’t the same (as Lee’s improved jack). And
I certainly wouldn’t want to work without a gauge, the most
obvious improvement.

My concern is more with the original question that started this
thread. Someone asked if nicks and a rough surface on the ram
might cause damage to the seals over time. This question
interests me, and I have now seen a couple of thoughtful replies;
unfortunately of varying opinion. Maybe there will be no
agreement or final answer for this one.

Thanks for all the great you share on the forum.
I’ve learned a lot from you and most recently you have solved an
old mystery for me, Re: tumblers, steel shot, etc.


As with all products, there is a wide range of quality.  The
common car jack is the wrong size for most presses and poorly

I have a keen interest in tools, in crafts and in metal smithing
(but none in jewelry making). This interest leads me to
examine the tools manufactured for many crafts. A large
majority of them are put together from common industry standard
parts such as hydraulic jacks, rams and fittings, pneumatic
actuators and rams, common air valves and fittings, electrical
and electronic parts.

Add a lot of furniture, a good paint job and a house label and
you have an expensive “custom made” craft tool but nothing had
been designed or made specifically for that machine that others
cannot reproduce by buying similar parts and putting them

So when a particular crafts machine sales person says that they
made special modifications to make their machine unique those
modifications are cosmetic. There’s not much point in doing
major rework on components such as a hydraulic ram that one
cannot save big money by getting a better quality component from
an industrial manufacturer specializing in hydraulic rams.

Kelvin Mok (

Home: (780) 463-4099 | Home FAX: (780) 430-7120



While in 99% of the cases your statement is prpbably true in the

case of the Bonnydoon Engineering hydraulic press it is not the
case. Lee Marshall is a mechanical engineer, he has designed
and built the frame and tooling attachments for his series of
presses. They are cut, turned, milled, drilled and welded in
his shop from raw stock. The hydraulic jack is an import. He
looked at a lot of jack manufacturers to find one that was of
reasonable quality, most asian import jacks and in fact tools in
general are junk. But there are some companies that make better
quality tools. The other thing he was looking for was a jack
with spare parts available. Now you can buy a jack from a
manufacturer here in the states that is of better quality but it
will cost two to three times as much for a jack from a company
like enerpac or power team. He then modifies the jack by
drilling and tapping a guage port and replacing the release valve
with a “tee” handle valve stem for convience I belive he does
some other modifications but I do not remember exactly what they
are. The jack base plate is cut and drilled to allow mounting in
the press frame. He sells the 20 ton power unit with guage for
$295 my enerpac 20 ton jack with guage was $595. So Lee Marshal
is providing a good quality power unit to fit a custom built
press frame for a very reasonable price.


James Binnion Metal Arts
4701 San Leandro St #18
Oakland, CA 94601



To add to the confusion:

the nicks will affect the seal if the piston ram (the thing with
the nicks) travels past the seal (which is at the top of the
housing) If however, the nicks are, say, at the very top of the
ram and you never let that part travel into the housing and past
the seal, by not collapsing the jack all the way, the damage
will not go any further. I have seen many rams with varying
degrees of damage, most of which are still in service, but
obviously the damage will hasten seal failure, which is a type
of rubber (many different types).

On larger equipment, a damaged ram, unless severe and causing a
leak, is almost always left as is (except for careful
filing/smoothing) because larger rams replacement easily runs
into thousands of dollars. And the seals handle small nicks
quite well, as long as they are not sharp. Larger and smaller
hydraulic rams are similar in construction.

And I suppose I should say that if you want to purchase a jack
with damage because the price is right, the only way to tell if
a 20ton ram is going to leak is to put it under a twenty ton
load. And even then it may not leak this week, but might next.
I’ve seen some leak with slight damage and others not leak with
major damage.

I was an electric/hydraulic troubleshooter for Food Services of

John g


Hi Daniel: I’ve wanted to put a gauge on my jack, but was
concerned about getting metal chips into the oil chamber when
drilling and tapping. Could you describe the procedure you used
to attach a gauge? Many thanks,

Joe Dule


Hi Joe, When i used to drill and tap hydrolic jacks to put gauges
and air operated automatic pumps on them(occasionaly)… I would
take a cloth strip and slowly insert it past the area that i want
to drill and tap…slide a flat piece of Brass or bronze into
the hole … this is so that when you drill the hole you won’t
scar the inner wall … tap the hole(use some oil on the tap)
you may need to use a flat bottom tap Instead of a tapered tip
tap( again , use the flat piece of Brass or Bronze inside the
hole so you don’t damage it (usually a stainless steel ball goes
back and forth in this area or the release valve) that is why it
is necc. After all tapping is done,try using a small magnet to
remove as much metal shavings as possible…you could also
airblast the hole with an air gun if you have a compressor
nearby… now remove the cloth and you should have a nicely
tapped area to insert your Gauge. I prefer glycerine filled
gauges… they are more accurate.You may also take the jack down
to your local hydrolics shop and ask them exactly how to do
it… i have always found them to be very helpful