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  • flat bar bender progress

    Most of the mechanical work is done on this project. Here's a few pics of it as it is now.

    [IMG][/IMG]

    A close up of one side showing the guide which keeps the bottom die plate perpendicular to the uprights

    [IMG][/IMG]

    A close up of one of the spring retainers. I have a range of about 2 inches by pulling the pin and repositioning the retainer on each side. When the bottom die is higher up for bending flat bar, these will be set higher. When the upper and lower bending dies are removed, there's about 5 inches of space that I can use for different pressing operations. These retainers will then be set lower. I don't want to stretch the springs, nor add too much to the pressure required from the jack when bending, although that would be so minimal by comparison as to be inconsequential.

    [IMG][/IMG]

    A close up of the upper die. I have a 60 degree V on it at present, and I stopped the milling with about a sixteenth of flat left on the bottom edge. I subsequently rounded that over by drawfiling, then sanding a little. I'm not sure if that is 'sharp' enough, but that's my starting point. I could have kept the angle down to about 50 degrees, which would have left a bit more strength at the edge, but again, we'll see how this works.

    [IMG][/IMG]

    The upper die can be slid out easily, so I can alter or repair it without much fuss. The bottom die- well, I don't have it made yet. Considering the time I've spent on this already, it won't stretch much for me to build a parallel round bar type of bottom die. There will be four carrier blocks on either side of the upright that sits on the bottom plate. These blocks will bolt through the upright (that's the 1 1/2 x 3/8 bar going horizontally above the plate) and each will have a saddle for the round bar to nest into. I'll be able to space them away from the upright by using washers, so I can adjust the spacing of the bars to suit. Without washer spacers at all, the bars will probably come close to touching, which will give a very sharp bend if the material is not too thick.

    The one question that remains is what diameter the parallel bars should be. The smaller the bars, the tighter the bend can be, but I'm looking for what's practical. I'm thinking 1 inch diameter bars. Too small and they will flex between the blocks that carry them.

    Because I want to also eventually use the mark-free bending method with half-round bars, I want to get the right diameter for the bars now, so I only have to machine the blocks once.

    Anybody that doesn't like my pvc tube base can come over and paint it for me ha ha. I figure that one day I'll put something useful inside that tube. I could also sandwich a piece of thin plywood or something between the bender and the tube to make it look a little more finished, but I'm not worried about it. Besides, the rails being mounted the way they are across the base tube- there's got to be an additional use for them - maybe I can add a small diameter rod rolling mechanism there- hmm
    Last edited by darryl; 06-06-2011, 01:52 AM.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    Nicely done darryl. If I had something like that around my shop I'd use more brackets. I have a 20 ton HF press and thought of coming up with a mod to it but never seem to get around to it.
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    • #3
      I built one that looked remarkably similar... built a bar bender, and a flat stock bender, and a "driveshaft press"... along about that time Chevy started pouring plastic into the driveshafts and you had to "shear" them out in a press.

      On the bottom, I welded a piece of 2x2.. so it'd drop into the socket on the truck, and workbenches. Now I have them sockets everywhere including the John Deere..
      Excuse me, I farted.

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      • #4
        Thanks for the comments. This is going to be very handy around my shop. I almost wish I hadn't bought the 3 in one sheet metal machine, or that I had bought a better one to start with. It has been handy, though, and the other sheet bender I built takes over where that one reaches its limit. Now the new bender will take over where the last one is over-stressed for the job. I missed my chance to get a half decent finger brake, but oh well. That can be a future project.

        No one has suggested anything regarding the size of rod to use for my bottom die assembly, so I've kind of settled on 1 inch diameter. Partly because I have it on hand, but mostly because the math works for an acceptable tightness of bend down to about 18 ga., and it will spread apart to handle everything thicker up to some maximum thickness. I'm going to experiment with a 45 degree upper die, with some relief past the 'breaking edge'. In other words, the 45 degree faces will start off at about 48 degrees, then at about 1/4 inch or so from the edge it will turn into 45 degrees. If I press a material into the bottom die with this, bottoming it out, the material should come out at a perfect 90, after springback.

        That experiment is down the road. One thing I would like to do fairly soon on is mill a half-round groove in the upper die and insert a piece of music wire along it. This will become the edge, it will be replaceable, and it will define a perfect round to the ID of the bend. It's not critical that this happens, but I just think it would look good and would probably be less stress in the material being bent.
        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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        • #5
          darryl,

          Would you have time to post some photos of the bends it makes?

          Edit: Oops... I misread - it's a "project in progress"!

          .
          Last edited by Mike Burdick; 06-06-2011, 10:50 PM.

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          • #6
            I'm just starting to cut the parts for the bottom die assembly. Don't know how far I'll get tonite.

            In thinking some more about this bar diameter, and comparing it to the normal V, I see something happening- with the V, the support edges are always the same distance apart. With the 1 inch bars, the initial distance between the edges would start at 1 inch, then narrow down to about 1/2 inch for a 45 degree bend. Once I subtract 2.8 times the thickness of the material, which is about what it would become, there's not enough space to be able to get the full 45 degree bend, and the support points would be basically right under the corner of the bend. The bars would have to be further apart to begin with, and I wanted to avoid that. So- that means a smaller diameter bar is needed.

            I knew this effect was there, but I underestimated how quickly the support points would come closer together. I think someone earlier on in this thread said something about this-

            So now I'm going to draw the geometry for some smaller diameter rods, and see if I can arrive at some kind of an optimum.

            Well that didn't take long. Looks like it will be 5/8 diameter bar. I will definitely need four support blocks over the seven inch length. Ok, back to cutting. Just got a new blade for the b/saw- a lennox diemaster II. It's obvious over just a few second of cutting that it's a good blade.
            Last edited by darryl; 06-07-2011, 12:16 AM.
            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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            • #7
              Nice job Daryl. That looks a lot like a design some bladesmiths use to press damascus billets.

              "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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              • #8
                THE Piranaha break, the lower is a square block with four different angles cut into it. on the end, a pin in the center.. the holder is just a socket with two alignment flatbars to center the pin.. it lifts up, spins around for another side, then drops back in.. THE top knife die, it stays the same.. This is mostly used for 3/8" or thicker stock up to 12" wide.

                All tools are a work in progress to be modified as needed. All the ones here have been modded, including the 5 foot pan break, it has a degree wheel on one end.

                Nobody I know with a HF 3 in one break is happy. two are cracked. They are kinda flimsy.

                I have a 12" finger break I am happy with.. I have bent 1/8" x 3/4" stainless tattoo machines up in it.. it weighs about 200lbs.. Not sure about the brand, looks like a grizzly but I didn't buy it new.. off a auction.. For a quick small electrical box, it is tops.. the 60" gutter break here.. It is like oragami, figuring which bends to do first so you don't close yourself up where you can't get in, or out of the break..

                There are HUNDREDS of types of sheet metal breaks.. I never realized that till I looked on google books.. some have cross rollers to "roll edges". Special buttress edges.. etc.. Some of the things I found that have already been invented is tools that "make" a cowl by rollers and pattern, inventor made them for a major car company for $5 each.. He kept that cow that gave the milk, sold the milk.

                I think the Home-made units are most fitting to the current need and work at hand.

                Not sure what you are working on, but a roller-bender can do amazing things and dies are quickly made on a lathe. Plus rolling a item through? you are not limited to width restrictions of a normal break.
                Excuse me, I farted.

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                • #9
                  I got the bottom die assembly to a usable state tonight. First couple pics show the bars and the support blocks.

                  [IMG][/IMG]

                  [IMG][/IMG]

                  Here the bars are positioned as close together as they will go, which leaves a 1/8 inch space between them.

                  [IMG][/IMG]

                  And here they are as far apart as they will go. I will be making a few spacer strips which will just drop down over the bolts between the supports and the center plate. All I need to do is loosen the bolts, pull the support blocks apart, then insert the spacers, one per side, then tighten the bolts. The bars just lay in place without bolts or pins. The upper blade has been removed just for the sake of these pictures.


                  [IMG][/IMG]

                  Preliminary tests show that it works very well. Thank you to whomever it was who suggested the parallel bars- I bent a test piece and couldn't even see a mark where it contacted the bars. This first bend is the nicest bend I've done ever on anything. With the bars close together, the material very quickly reaches a point where it pinches down between the bars. For thin sheet this gives a very crisp bend. I tested some 3/16 flat bar at this spacing, and though it would only go about 30 degrees or so, the bend was just as crisp. With the right spacers, I'll be able to keep this crisp bend up to about 120 degrees. I'll end up with a chart showing the spacer thickness to use for any particular thickness of material, and the degree of bend it makes with the tightest radius possible. This is the point at which the material is pinched between the upper and lower dies, and the actual corner forms to suit in free air. In other words, it would be the tightest bend possible for the particular thickness of material.

                  Of course you don't have to operate it this way. You can do air bending with the dies further apart, which takes less pressure, doesn't make as tight of a bend, and relies on the operator to pump the jack to just the right point. This is the mode that the bender will likely be used in with thicker materials, and where the bend radius doesn't have to be so tight.

                  From my minimal testing so far, I'm a happy camper. In the next day or two I'll do more testing and show the results.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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