Thought I'd make an instructable about this project from last year. I do a lot of strange metal folding for my work and found that there are limitations to the standard pan brake folder due to the shape of the clamp teeth. A brake press can get around a lot of those issues but you need a myriad of tooling and a lot of money, space and electricity to have and run a decent machine. I came up with the idea of putting a small pan apron on the front of a shop press but the adjustable bed on a standard shop press would render the apron inaccurate and hard to use so I went with my own frame design with a rigid bed. I have since made a heap of different top clamps and tooling for this press. It's a very versatile little machine and has proved invaluable to my business. The build cost can vary but if you have access to some heavy steel off cuts you can get away with building this for well under $300.
As a side instructable I'll show you how to invert the 20 ton ram so that when you are pressing you can use the smaller end of the jack instead of putting the massive body of the jack into your work area. This allows for increased freedom of workable area and greater versatility with regard to the types of clamps and tools you can make and fit.
The drawings here are a general overview and should only be used as a guide, you will see from the photos that I altered the final build from the original plan to accommodate a specific job I needed to do. This folder can fold 2x600mm mild steel on the pan brake section and 600x4mm or 100x6mm on the brake press.
Step 1: Making the Bed:
The bed is made from a piece of H beam 200x200x8mm 900mm long and 50x50x8mm angle iron.
1.1 Weld gussets at the ends of the beam and sections of 50x50x8mm angle iron across the web (toes in) every 200mm on both sides to strengthen the beam.
1.2 Then I notched out a recess for the hinge to operate in. (in order for a pan apron to operate properly the pivot point needs to be as close to the center of the hinge as possible, this means that the middle of the hinge should align with the two folding edges of the apron.
Step 2: Making the Frame
The frame is made from 65x65x10 mm angle iron and 18x950mm reinforcement bar
2.1. cut 4 pieces of the angle to 500mm and arrange on the bed so they are at each end standing up with toes facing inwards make a 750mm space between them (length) and a 30mm gap between then (depth).
Tack them into place making sure they are square with the base, parallel with each other and level (Measuring diagonals with a tape and use a set square).
2.2. cut 2 pieces of angle @ 880mm and 4 @ 180.
The 2 880mm pieces go across the top (toes at the bottom facing inwards) with a 50mm gap between so that the angles across the top over hang the upright angles by 10mm to the outside. the 180mm pieces go between the two top angles at each end and 40mm out from the centre. make sure everything is level and square before you tack it into place.
2.3. the reinforcement bar acts like a truss across the top to add strength. It should be bent in the centre @ around 10 degrees and have a piece coming up from the centre of the angle iron frame to the centre of the bend (You could replace this with an adjustable nut if you want some preload action) Tack it into place.
2.4. Welding. Remember when you are welding this: This frame will need to withstand the forces of the 20 ton jack without defecting. always make sure you follow correct welding procedure. All of the structural welds on my project were done with an arc welder because I feel it is more reliable for strength and easier to spot a defect on an arc weld. some of the frame design may be considered by some to be overkill but again, safety is as high a priority as function. This is not a project for the haphazard welder. you don't want this machine to fail under load. you have been warned. ...carry on welding.
Step 3: The Apron
3.1.The apron is made from 6mm plate 900x300mm it was rolled along the width to create a slight horizontal radius (5mm datum) the radius face bulges to the front of the apron, It's not completely necessary but this adds rigidity and resistance to the apron.
3.2. The sides of the apron taper in to allow clearance between the legs of the press. 40x6 mm angle is welded down both sides of the apron. A reinforcement bar (same fashion as top of frame) goes along the base of the press, this makes for a good handle.
3.3. fit the apron to the press: I made my own out of some large hardened nuts that i drilled out and some hardened rod but you could use heavy duty machined trailer hinges for this, try to find some with grease nipples so they are easier to maintain. Remember: the center of the pivot point needs to be aligned as close as possible to the folding edge line. its good to leave around .5mm gap between the folding edges. Once the apron hinges are tacked into place and you are satisfied it will swing straight without the apron contacting the bed you can weld them into place.
3.4. cut a piece of the 65x65x10 angle iron to fit across the top of the apron, needs to bolt on as you want it to be removable and changeable for other sizes.
Step 4: The Base and Air Box
The base is made from 75x50x3mm galvanised RHS, it's two A frames with a piece of 75x50 tying them together. I was going to make this bolt on so it's more transportable but I just welded it in situ and regret nothing.
Later on I added a shelf for the clamp bars.
The air control box is just a few regulators with a foot operated circuit and two outputs, I got the pedal off ebay for $5 and ran the send and return air hoses through an old bike inner tube to neaten it up (the other one operates a sheet metal punch but that's a whole other instructable that I haven't done yet.)
The foot pedal output was simply sent to the air input on the air over hydraulic bottle jack.
Step 5: Invert Your Bottle Jack
I have a lot of people argue with me about how a bottle jack doesn't and can not work upside down, It just isn't true. The reason why the bottle jack won't work upside down is because it picks up the fluid from a small hole in the bottom of the jack. When you turn the jack upside down the fluid runs to the top of the jack so all the hole is doing is sucking air. Air can be compressed so it can't move a piston under load.
The solution? ..You can fit a straw to the intake hole so that it picks up from the top end of the jack when inverted. The images are of a smaller one that i did for an apple press but the principal is the same
5.1. Make sure you are working in a clean environment. Metal shavings, dirt and hydraulic fluid are not friends. remove the rubber plug and drain all of the fluid from the jack into a bottle or tray.
5.2. Remove the large nut from the top of the jack. you will need a vice and a very big spanner, I had to make my own spanner out of angle iron but it worked a treat. put the cast iron base into the vice and turn off the nut
5.3. Very carefully remove the outer bottle from the jack making sure not to damage any seals in the process. you may need to tap it a bit with a wooden mallet to unseat it from the seal on the base.
5.4. Weld up the filler hole on the outer bottle, and drill a new filler hole about 40mm from the base end.
5.5. now is the point to fit the straw. Locate the hole which the fluid draws from, you can do this by putting some fluid across the surface where the holes are and pumping it a few times, watch which hole is drawing fluid. I have used some thin but rigid rubber conduit and cable ties against the inner column to keep it straight and directed to the top of the jack. I tried using copper brake line but I couldn't get it to seal properly around to hole, the rubber squeezed nicely into the hole and sealed the edges. this may restrict the flow a little bit but given its air over hydraulic and you don't need to hand pump it's fine.
5.6. If you are sure there is a nice seal around the base of the straw you can put the jack back together and re fill with fluid. There may be some residual air in the system, this can be bled by fitting the jack upside down into the press and actuating/releasing the cylinder a couple of times. You should hear the air escaping from the release valve.
5.7 The release valve has a few chain links with a rod and handle welded on it so as to extend through the side of the frame for easy release access.
You can get these air over hydraulic jacks from hardware/tool stores or online, they shouldn't cost more than $150.