Last weekend, I dropped into my favourite tool store to see what I could use my birthday gift card on. Nothing I needed, but I saw a 20-ton shop press that was covered in "Does not work" stickers. Regular $400 on for $150 - no warranty, as is.
It's hard to resist an orphan, especially when it involves a challenge. The list included a ram that would not retract (Fred had pumped it down with a 10-ton pump from a porta-power set) and a pump that did NOT work.
The ram was relatively easy - the internal tension spring wasn't attached at the top end. Poor design, poorly executed. They aren't known for full retraction, but will pull up from the work when the pressure is released. Good enough for me.
The pump was another story. On the inlet from the reservoir, the steel ball check valve was above both the tank hole and the hole running to the piston chamber. Nothing to stop the oil from getting pushed back into the tank when the handle is brought down. I drilled the hole for the ball down between the two holes and set the ball with a punch.
There was no check valve after the piston chamber, so the oil came back as soon as the handle was raised for the next stroke. The passage wasn't even machined to take one.I drilled down to allow a 1/4" ball to be added, with a spring between that ball and the ball valve for the pressure release screw. That allowed me to get some movement out of the ram, but not enough to be useful.
Today, a morning thunder storm convinced me to stay in the shop and replace the pressure release valve and final check valve with larger ones. I used a 1/2"-20 bolt for the new valve shaft and a 7/16" ball for the release seal. The old 5/16" ball from the release valve became the new pump check valve. Here's the old shaft beside the new one (installed).
I had to do some tweaking, but ended up getting nearly 15 tons out of it. At that point, the high-pressure bypass valve opens. If I really need the whole 20 tons, I'll fine-tune the HP valve. For now, it has a LOT more power than my 3-ton arbor press. Definitely left an impression on a piece of birch plywood. BTW, the hose clamp on the ram was so I could keep track of movement, when there wasn't much to see.
It's hard to resist an orphan, especially when it involves a challenge. The list included a ram that would not retract (Fred had pumped it down with a 10-ton pump from a porta-power set) and a pump that did NOT work.
The ram was relatively easy - the internal tension spring wasn't attached at the top end. Poor design, poorly executed. They aren't known for full retraction, but will pull up from the work when the pressure is released. Good enough for me.
The pump was another story. On the inlet from the reservoir, the steel ball check valve was above both the tank hole and the hole running to the piston chamber. Nothing to stop the oil from getting pushed back into the tank when the handle is brought down. I drilled the hole for the ball down between the two holes and set the ball with a punch.
There was no check valve after the piston chamber, so the oil came back as soon as the handle was raised for the next stroke. The passage wasn't even machined to take one.I drilled down to allow a 1/4" ball to be added, with a spring between that ball and the ball valve for the pressure release screw. That allowed me to get some movement out of the ram, but not enough to be useful.
Today, a morning thunder storm convinced me to stay in the shop and replace the pressure release valve and final check valve with larger ones. I used a 1/2"-20 bolt for the new valve shaft and a 7/16" ball for the release seal. The old 5/16" ball from the release valve became the new pump check valve. Here's the old shaft beside the new one (installed).
I had to do some tweaking, but ended up getting nearly 15 tons out of it. At that point, the high-pressure bypass valve opens. If I really need the whole 20 tons, I'll fine-tune the HP valve. For now, it has a LOT more power than my 3-ton arbor press. Definitely left an impression on a piece of birch plywood. BTW, the hose clamp on the ram was so I could keep track of movement, when there wasn't much to see.
Mike
If you can't get one, make one.
Hawkeye, proud to be a member of MetalworkingFun Forum since Jan 2013.
If you can't get one, make one.
Hawkeye, proud to be a member of MetalworkingFun Forum since Jan 2013.