Building a press. What size table support rods.

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Hi all,Im currently building a press. I have a 20ton jack to put on it but trying to find a 50ton so im building to those specs now.I remember seeing something about this before but cant find it anymore.My uprights are made of C channel. Where the rods will sit is 10mm thick. What diameter rod would I need to hold up to 50tonCheers,John
Reply:look at an existing commercial one and duplicate it, they have already done the engineering..
Reply:What you make the pins out of will also have an effect. Mild steel will take less load than say using grade 5 or grade 8 bolts as your material..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:my 20 ton harbor freight press is 2" x 4" x .2" C channel with holes about .82" diameter. I suspect mild steel but don't know. I actually need to pick up some bolts for it, I think 3/4" will do or 20mm would do too. With a slenderness ratio of about 5 I don't know whether the limit is shear, bending, or bearing area. Mine came from a friend without the original pins, and instead uses some 1/2" extensions, which I ought to replace with decent nuts.Lincoln 175HD
Reply:Used 1"dia  with a 20 ton jack. Uprights and bed are 5"x 2.5" channel.Bed is reinforced with 4.5"x.5" flatbar.
Reply:50 ton at work has 2 rods (1 1/4) on each side. Attached ImagesLast edited by Scott0303; 10-22-2012 at 01:50 PM.__________________Miller MM252Lincoln AC Buzz BoxCentury 155Victor O/A
Reply:Hi, mild steel will break when a cross sectional area of 1 sq inch has a tensile stress of 27 tons applied to it.Divide that by a safety factor of 3 and you get the 1 sq in resisting only 9 tons.....if you exceed the tonnage you reduce the safety factor.A bar of mild steel 1.3" diam is approx 1 sq in.Ian.
Reply:A press puts those pins in shear, not tension. Plus, there are 4 of them.Lincoln 175HD
Reply:Hi, yes I know,  the shear stress on Mild steel is also around the 26 tons per sq in mark.......can't be absolutely certain on the figure......so for 50 tons each pin has to resist 12 1/2 tons + the safety factor.I was pointing out the shortcomings of the top beam ( and table) when you apply the tonnage as these are the most difficult to design unless you just design with over engineering to be safe.With a beam, the beam will deflect ( has to) before it can resist the designed load.Personally, with a press of this tonnage, (50 tons) I would make the ram moveable in that it can be moved as close to the side frame as possible to resist the bowing of both the table and the top beam when the tonnage is at the max....the pins and top bolts on that side must then resist the full 50 tons. force.Ian.