I wanted a hydraulic press for my shop, and didn't really like the design (or the price) of commercially available ones. So I decided to design and build my own.
Above are most of the materials I used: One 20-ton hydraulic bottle jack, Three steel theater weights, two 3/4" threaded rods, 8 nuts, 8 washers, and 2 extension springs (I ended up using different springs than pictured above.) I also ended up shrouding the 3/4" rod with some blue PVC tubing.
Here are all the materials assembled, with the blue PVC tubing added to the threaded rod, sandwiched between the top and bottom plate. The theater weights were great because I didn't have to drill any holes for the 3/4" rods.
I drilled and tapped holes for four 1/4-20 nuts to hold my extension springs (these springs will return the press to it's "open" position.)
Extension springs added on opposite two corners, applying tension between the middle and bottom plates.
A bit smaller now...
Hard to see, but the coke can is still in there... somewhere.