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I bought the smallest hydraulic jack at Harbor Freight to increase the force of the press. My estimate is that when the jack is pumped with moderate effort, with only a half of the handle (the handle can be assembled to be twice as long as on the picture), the arbor press produces approximately 10 tons of downward force.
As a gauge of force, I used a small bearing ball between two mild steel plates. Without the jack, the ball would only make small dents on the surface of those plates. With the jack, the ball fully sank and the distance between the plates was reduced to almost zero.
