Depends what you're working on. Crankcase bearings only need a 5 ton but cranks vary widely. If its a mini to 125 a 20T is ok. If you're looking to press a 250 or 500 crank you'll need a 30-50T with a strong frame. If you want to press a Maico crank then go to a diesel repair shop and borrow theirs:cool:
The hydraulic jack isn't as important as the frame structure. I bought a press from Harbor Freight and Enco and broke them both on the first try pressing a 250 crank and I know it didn't require the full capacity of the jack. Look for a press with sturdy support to prevent it from whipping sideways.
Randy Hawkins, the off-road racer owns a company in Traveler's Rest, SC called American Fabrication. They make a good press and private label them or sell direct. However I don't know the web site or phone number. Maybe somebody else knows?
I remember pumping it up to max pressure and having to tap the frame on the side with a twenty pound sledge hammer to get the crank to move.
Later at an auction we scored an air over hydraulic job that was the business.
You could try local auction houses or call around to some machine shops and see if someone has a used one.
You might find a big daddy from someone for cheap.
A good source for a used 50 ton press would be a used equipment reseller that buys from auto parts stores. Barks Equipment in Cape Girardeua Missouri is my personal favorite. Or just go to stores in your local area and see if anybody wants to sell and old press. Nowadays little auto parts stores are getting bought out by chain stores and eliminating their machine shops. These big equipment resellers buy stuff for pennies on the dollar, because their biggest expess is shipping the equipment.