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bending brass hinges slightly but neatly

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  • bending brass hinges slightly but neatly

    In building the New Yankee Workshop Federal style game table, I need to bend some brass strap hinges to a 17.75 inch radius. They are about 1/8" thick, 3/8 inches wide and 2.5 inches long on each side ( 5 inches OAL when open). There are mounting holes with countersinks that might buckle if I get carried away and the middle part has the pin and is about twice as thick, it wouldn't bend at that point very easily. Any suggestions before I try my own ideas and ruin a pair of $24 hinges?

    These are mortised into the edges of a table that folds onto itself to only take up half the space for storage and yet fold out for a full round table to play cards on. If the hinge pins of both hinges aren't in the same plane, they will bind when moved so that is why they need to be bent as required to fit the edge of the table. Any ideas? Thanks--Mike.

  • #2
    Mike, how about making a male wood die equal to the inside radius minus half the brass thickness and also make a female wood die equal to the inside radius plus half the brass thickness and pressing the two dies together with hinge inside maybe using a bench vise. If there is too much spring back the hinges could be annealled or a new set of wood dies of smaller radius made.
    Gary

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    • #3
      It never ceases to amaze me how all Norm Abram's cuts are perfect and everything fits together with no gaps. On top of that, he builds pieces of furnature in less than 30 minutes.

      One thing I've noticed in most all his shows is that he uses a lot of jigs. If you make a bending jig, you should be able to get both the same. Yeah I know it's a lot of material but if you want it right, make a jig. I've made wood bending jigs to bend car drip rails and trim.

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      • #4
        Bend them around a form, but back them up with a piece of flat bar, with the hinge strap pinched between the bar and the form. Both the bar and the hinge are bent to a radius at the same time. You'll have to sacrifice a piece of flat bar probably 6 inches longer than the length of both hinges. Each hinge is bent with a fresh end of the bar. There's going to be some springback, so for the radius you want, maybe make the form with a 15 inch radius. If you'd be concerned about over-bending, maybe use a 17 inch radius and plan on reducing that on the form after you make a bend and test it. My hunch is that a 15 inch radius will be about right.

        Put some kind of tape on the flat bar to protect the brass before clamping the setup together. You'll have to get the bulk of the clamping pressure as close to the hinge pin as practical, or you won't get any bend for the first part of the strap.

        For that width of the brass strap, I'd be using flat bar that's about 1 inch wide by 1/8 or so thick.
        Last edited by darryl; 04-04-2007, 02:27 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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        • #5
          Originally posted by gary hart
          Mike, how about making a male wood die equal to the inside radius minus half the brass thickness and also make a female wood die equal to the inside radius plus half the brass thickness and pressing the two dies together with hinge inside maybe using a bench vise. If there is too much spring back the hinges could be annealled or a new set of wood dies of smaller radius made.
          Gary
          I think Gary has a good idea. Make the whomping mandrel out of end grain oak or maple and not bigger than 1 - 1 1/2 inches square and maybe wrap the business with some wire to act as a ferule around it to keep it from splitting out. A little patience and a not-too-big BFH will have you wrapped up in about an hour with perfect bend and no dimples or scratches to deal with. The secret here is to not try and get it done in 10 massive whomps of the BFH but rather a multitude of lighter whomps
          Last edited by Your Old Dog; 04-04-2007, 06:35 AM.
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          • #6
            Is the bend the "Easy Way" or the "Hard Way"
            I'm not clear on this.
            Norm should have given some instruction on this
            operation.
            Kap

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            • #7
              underlayment plywood of baltic birch may not be pretty but the stuff is "hardishly stout". You can make spinning forms from the stuff. Bending jigs (edge grain) from scrap size pieces would be a "piece of cake".

              The wood from scrapped pallets and skids is also not very pretty but makes fine BFH blocks.

              Always make the jig underradius because of spring-back.

              Then there is residual stress left, so if the part comes out a little to much bend just line the male jig with some card stock (old file folder, or masonite, or whatever) and open up the bend a bit with light taps of a hard rubber mallet.

              Hth Ag

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              • #8
                Could they be used as they are?

                I made a quick layout and you are talking about a [.176] bow in the hinge. Could the mortise that you must make be flat? [.125] deep at the ends and [.125 + .176] deep at the hinge point.
                I hope I understood the problem.
                Good Luck,
                Bob G

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                • #9
                  I'm not firing on all cylinders this morning, so please explain how a bent strap hinge will actually hinge.
                  Last edited by bhjones; 04-04-2007, 11:23 AM.
                  Brett Jones...

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                  • #10
                    Yeah, I thought that but it's a strap hinge not a piano hinge so if the pins are in line the hinges will operate

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                    • #11
                      The hinges look like miniature slap type staple guns from the side and the pins actually slide in a track inside the hinge to accomplish the 180 degree bend and still keep the table leaves (halves) close together in either mode--open or closed. The horton-brasses website shows them--the number is h-53.

                      The Horton guy said that Norm bent his in the vise. That sounded like lots of scratches and buckled metal around the mounting holes to me. This is for a charity auction next week and I don't have a lot of time to ponder a solution, so I asked you guys.

                      After reading the replies here, I got an idea. I still had the scraps from cutting the top out and they were obviously the right radius, so I put one in the vice on edge and used the inside curve as a mandrel and tapped lightly , but repeatedly on the inside of the hinges and it worked like a charm. Thanks--Mike.

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