Replacement jack for Bonny Doon hydraulic press

I have a Bonny Doon Hydraulic press that I purchased new in 1994. It
was not used for many years and the oil leaked out of the jack. I
called Rio Grande about a replacement jack and was told that the
jacks that they use in the new presses will not fit on mine. My
options would be to send the entire press to Rio to have it modified,
or to send the jack to be refurbished with new seals. They could also
drill a hole for a gauge. This would cost about $250. and does not
include the cost of the gauge. Does anyone know of a less expensive
quality jack that would fit my press?

Hi Kathy:

Your seals may not be dead, they may have just dried out from lack
of use. Try refilling the jack with hydraulic jack oil (available at
auto-parts places) and see what happens. Pump it all the way up and
down a few times every day for a week or so, and see if the seals
don’t tighten up.

If that doesn’t work, it’s possible to replace the seals. Not even
all that hard from what I understand. Messy as all get out, but not
that hard.

As I understand it, Lee’s secret for all those years was that he was
buying Harbour Freight jacks, then tearing them apart, replacing all
the seals, and cleaning them up into something that was actually
useful. You could probably get the ‘same’ jack–without the
rebuild-- from Harbour Freight today. It’s also possible to mount
your own pressure gage to them without too much trouble, so long as
you’re comfortable drilling decent sized (1/4" or so) holes in
steel-- [accurately]–, and then tapping the resultant hole.
Somewhere, I’ve got a ‘how-to’ PDF that one of my students forwarded
to me on exactly how to do this. I glanced over it, and it looks
simple enough. I can’t imagine the gage itself costing more than $75
at the most, probably much less. Let me know if you need any of this

Hope this helps,
Brian Meek.

Look in the Yellow Pages for Hydraulic equipment repair, or ask a
local farm equipment or heavy equipment (diggers, bulldozers and the
like) dealer. Either will be able to repair the Jack, or refer you to
the local company that can.

There is no real difference between replacing the seals in a jack or
a hydraulic cylinder.


I can't imagine the gage itself costing more than $75 at the most,
probably much less. Let me know if you need any of this info. 

When I last looked into putting my own gauge into a jack, I couldn’t
find one for less than $100.00, and finding stuff is pretty much my
specialty. That and the risk of ruining the jack while trying to
install the gauge made me throw in the towel on the idea. I bought a
Bonny Doon jack for my welded I-beam frame.

I also have 2 inch steel platen for top and bottom, custom made to
made the Bonny Doon so I could buy all their cool accessories, but
those I have yet to have welded in and threaded.


Hi Kathy

Brain is right Lee (Bonny Doon) used a 20 ton Hydraulic jack from
Harbor Freight. If I remember the key was extended and a gauge was
added. I had bought the gauge on line and I had even tried Habor
Freight’s 30 ton jack it was of same height and fit well.

Kenneth Singh
46 Jewelry Supply
Ring Tools Inc
Arjan / Karat46

Hi All,

I think that the thing to do is talk to Phil Poirier (www.Bonny Doon and click on the New Forum button). Putting new oil
in it and working the press may work… but chances are that it
won’t. New seals are in order… and will make you very happy when it
is working properly.

Phil does rebuild jacks. It is a much better thing to have him do it
rather than trying to do it yourself. It is messy and Phil has the

From what Phil has told me the companies that make the jacks
periodically change the way they are built. Manual jacks aren’t the
problem, but the jacks that are put into the all electric pump are
difficult to “rework”, that is the fairly expensive changeover
$250.00 or so. I had a seal blow in a jack (showing off to a new
girlfriend years ago), the jack sprayed oil all over her. :-[
Bummer… but the jack was rebuilt with stronger seals and worked
great. It didn’t cost very much either… I can’t remember but it
wasn’t much.


I have tried to end run Bonny Doon and Rio about the repair and
maintanence of my Bonny Doon press and have always ended up sending
it back to Rio or Bonny Doon and paying them to re-do the work
correctly (paying for the work twice). So while the work is not cheap
to have the “dealer” do repairs it is done right and any safety
concerns I have had about a third party working on my press have been

Sam Patania

Kathy - have you tried contacting Lee Marshall. I recall that with
some of his presses, he found that the seals needed to be replaced
if the jack wasn’t returned to the “resting” position after each use.
He replaced these seals without charge (you just had to get the jack
back to him). I know he is “retired” but he is still available to
talk to. Before you try substituting an unmodified Harbor Freight
jack, contact Lee and see what he says.

Sheridan Reed

Thanks to all for your suggestions and thank you Brian for the link.
I now know way more about this jack than I ever expected! At least I
have a few options if I can’t get this to work on my own.

As a new member to this group, it’s so nice to have this resource
and to see how helpful everyone is with

Kathy Gould

When I last looked into putting my own gauge into a jack, I
couldn't find one for less than $100.00, 

MSC ( has a number of pressure guages on page 4373 of
their catalog.

There are 2 inch diameter gauges with pressure ranges to, 600, 1000,
2000, 3000, 4000, 5000 & 6000 psi.

All have 1/4" NPT connections. the 0-600 is $11.86. All the rest are
$16.79 ea.

The item number of the 0-3000 lb. jack is: 56479280.

Usual disclaimer, just a happy customer.

Hi All:

Thanks Dave, I was about to chime in with something similar from

I’m not sure how many people read the whole article, but probably
the most useful tidbit was that he goes into some detail into how to
figure out exactly how much pressure the jack is actually putting
out, as measured by the gauge. The gauge only measures the working
pressure of the high-pressure manifold, not (directly) the actual
pressure applied by the end of the ram. To figure that out, you have
to get the area of the bottom of the ram, and figure out a
multiplication factor based on the gauge’s scale, and the area of
the ram surface. Very useful little bit to know.