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The Jaws of Crimp

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  • The Jaws of Crimp

    Once again I'm standing in the workshop looking at a piece of sheet metal I have laid out, with the bend marks drawn, corners defined, etc- but I can't fit it within the limits of my bender. This is a basic sheet metal box, but the corners are not all at 90 degrees- if they were I'd be in business. Two major bends are at about 45 degrees which means that the corners won't allow the bend to take place- unless I could reduce the length of the bottom V die to allow for that. Also I can't accommodate the height of the sides- I can only go up to 4 inches for that, and I have 8 inches of sheet on one side that has to clear the parts of the machine.

    Anyway, these details are not important to my question, which is- how do I make a bender which can reach in to the bend line ( I need about 10 inches depth of throat ) and kink about 4 inches of bend at a time?

    The tool might be easy to imagine- it's just some jaws with a pivot point more than 10 inches from the top and bottom V die parts, which can be about 4 inches wide. I would line up, bend about 5 degrees, move along, bend 5 degrees, etc. When the length of the bend line has been kinked, go again, adding another 5 degrees- keep going until the entire length of the bend has taken the required angle. I would likely overlap with the bender so that all the corners created are equally pressed.

    This was my method before I had a bender at all. I used the vise, some solid bar, and a hammer. Moving the piece back and forth in the jaws let me progressively produce a bend in sheet that was too wide to be bent all at once. It works- it doesn't leave the nicest job, but it can be decent.

    Now I want to dispense with the hammer and instead use a specialty tool to reach to the line and do the same thing. Probably would be powered by a 1 ton hydraulic jack, since I have a spare one. If the sheet stayed flat, the bender would angle itself as the bend progresses, or if the bender is stationary, the sheet would angle up on both sides as the bend progresses.

    Looking for ideas- I don't want to spend a bunch of money, since I don't do jobs like this that often. I'm willing to make something from materials on hand.

    One way I can see to do this is to use a press with a large enough opening between the towers. I would need about 49 inches to handle the width of a sheet- right now the job I have would require about 40 inches. A typical press with that much capacity is not going to happen in my shop.

    One idea I had is to arrange a floor mount for the bottom die, then hang something from the ceiling to carry the top die. I'd be using the weight of the floor above to provide the bending pressure, and I'd have to make sure I could keep the parts in alignment. I would probably rig up a lever to hand operate the thing.

    Or- I would attach parts to my steel column which is part of one of the home made machines. This column usually stands upright when not in use, and it's secured to the floor joists above and the stand below. A bottom die fixture could extend about a foot out from the column, and the top die would have a matching fixture which it could slide up and down in. I'm sure I could easily rig up a lever to operate that. Hmm- I think I have the answer now- thanks everyone.

    Still would like to hear ideas though-
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    Pics would help the analysis but it looks like you figured it out. In any case, many brakes have sections that can be removed so you can bite smaller lengths. From your description, I might suggest a beam that runs across the workpiece and fastened outboard, with "fingers" to reach the scribe lines.


    • #3
      Well, I 'cheated' and got the job done. I didn't make the crimper tool.

      Because the piece of sheet was basically going to be folded up to make a roughly 2 ft square by 5 inches high box, I notched the four corners out to start with. If it was going to have all four sides bent up at 90, it would have been easier, but two of the sides splay out at about 45 degrees, making the mating sides longer than my machine can handle. I ended up curling the corners inwards so it would fit within the columns of the machine. Because the sides are 5 inches high and the machine can only handle about 4 inches, I left two of the bends at less than 90. The bottom die edges are too close together to allow the machine to bend the 22 inch length of this sheet material, which is about 20 ga, so I laid a piece of 1x1 angle in the V. The supporting edges are now about 1-1/2 apart instead of about 3/4, so it made the job just barely possible. That also reduced the height capacity to about 3-1/2 inches, so I basically had to let the machine jam the already folded sides apart even more.

      When I had done all I could with the bending, I un-curled the corners, then folded the angles closer by hand. Then I set it up on a flat surface and placed a piece of rail inside, aligning it with the bend marks, then hammered all the edges in turn to tighten up the bends. That was tedious, and the piece of rail was almost too heavy to handle, but it went pretty well overall. Now I have a box with two 90 degree sides and two sloping sides- and hammer marks all along the bent edges. The corners come together fairly well, so now it's on to the inside bracing and the rest of the project. This box will mount on the back of my van, and will be a container for propane bottles, burners, a fry pan, some fire pots, etc- stuff I don't want to have inside. I mentioned this project a couple weeks ago, and I decided to go ahead with it.

      What's a good adhesive to bond sheet steel to square steel tubing? I don't want to have any screws or rivets showing on the outside, but on the inside I don't care. I'll probably be using PL 9000- that should be fine.
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


      • #4
        I might still build a helpful tool to aid in sharpening up poorly bent edges, but I'm thinking it sure would be good to have a finger brake in the shop- though I have no room for it. In time, I suppose-

        Meanwhile, the tool could be something like a giant C clamp- forget the hydraulic jack, but use a cylinder of some type and maybe a foot pump. I think you'd need both hands to manipulate the tool. Go only about two inches with the top and bottom dies, and round the ends of those to give a softer transition in the bend from spot to spot. I did start to look at sheet metal tools, but didn't see anything like what I have in mind.
        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


        • #5
          Henkel/Loctite H3000 is an excellent adhesive for steel to steel. I used to work at a place that bonded ballistic products for projectile protection and we used it all over the shop. Comes in a two part dispenser with mix nozzles and takes a specific gun but works like a champ. Only way to bust it that we ever found was with torch heat.