I recently picked up the 20 ton air over hydraulic bottle jack to replace the original one on my Harbor Freight 20 shop press. Anyone that has one of these presses knows that the "jack plate" that the jack sits on and has the ram welded to it is **** poor at actually keeping the ram straight. I also have the older orange version that's fully welded together and is pretty out of square. I believe the newer gray ones are bolted together and have several other improvements.
First I had to grind off some welds since the ram was actually welded to the jack plate out of plumb. I heated it up with a torch and wacked it into square. Then I removed the "guides" from the end and made new ones with some mounting holes. I spaced them further out so I could sandwich pieces of UHMW plastic between them and the uprights. I also welded on some small pieces of angle to keep the jack base from sliding around. In the original design the jack just sits on the jack plate. Now it glides up and down on the supports very tightly, no wiggle and perfectly plumb.
I've also added the T-handle to the front of the jack release valve for quick operation. I also turned a collar for the ram so that I can eventually swap different size press punches and accessories.
I need to get some more material for the next round of improvements.