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  • Bent Miter operation

    How would you cut this using a machine? The dimensions don't matter - the assembled part should explain it all. It is a 90؛ quarter round at one end of the gap, square at the other, the left side wraps around the quarter round so the gap is Circumference/4 wide.

    To get you started assume a radius of 1 and go from there. Any flexible but non-elastic material that can be made to bend in this fashion.

    This is a common construction method in the PNWet that some of you locals may recognize. It is a bent wood box corner.

    Last edited by dp; 09-04-2011, 11:06 PM.

  • #2
    I've seen those bent-wood boxes in the museum on the UW campus, made by the Haida, I think, or some related tribe. I'll be interested in the answer to your question.

    Do you know how the Indians made the cut without a machine?
    Allan Ostling

    Phoenix, Arizona

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    • #3
      A Scroll Saw.

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      • #4
        Originally posted by aostling
        I've seen those bent-wood boxes in the museum on the UW campus, made by the Haida, I think, or some related tribe. I'll be interested in the answer to your question.

        Do you know how the Indians made the cut without a machine?
        Not sure. Did Indians have Coping Saws?

        Really though, they were using stone cutting tools when the Europeans arrived, or are you referring to India Indians?

        Chris

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        • #5
          Originally posted by aostling
          I've seen those bent-wood boxes in the museum on the UW campus, made by the Haida, I think, or some related tribe. I'll be interested in the answer to your question.

          Do you know how the Indians made the cut without a machine?
          They also make simple 45؛ bent miters, but this one from a museum in Victoria caught my eye as I'd not seen the style before. The Haida had access to volcanic glass and there is quite a bit of flint on the northwest coast. An original pre-contact bentwood box is worth a load of money though if I had one I'd give it back. They were used for all manner of things. I thought it would be an interesting project to try this particular corner method. The final corner is stitched. The bottoms are either stitched or inset and the box wrapped around it.

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          • #6
            Originally posted by Chris S.
            A Scroll Saw.
            I think a series of form cutters in a shaper can do it. A chisel can do it in wood, of course, as can a plane, but to do this in steel or aluminum requires a machine.

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            • #7
              In wood and some plastics, that would be two passes with a router. I'd imagine metal to be similar but the radiused tool would be a bit more rare.

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              • #8
                Plow a groove with an endmill first,then grind a custom form mill to mill the radius and undercut.Could probably start with a dovetail cutter for the blank and grind the radius in it,
                Last edited by wierdscience; 09-05-2011, 10:37 AM.
                I just need one more tool,just one!

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                • #9
                  I'm not sure what that joint is called. As was said you see it in Haida and Kwakiutl storage chests.

                  Can't make that joint with a rotary cutter. It has to be shaped. Do the math. A rotary cutter has to be twice as wide as the profile it cuts and add for the shank. The width from the tangent to the shoulder is r * pi / 4. The gap is 0.2146 * r. Steam to bend.

                  It makes a strong joint. Handsome too: the grain wraps right around the corner. I've tried them on narrow stock and a bandsaw with a skinny kerf works well but the interior angle has to be incised if the joint is to be invisible. Back in the day the native craftsman split and joined 30" wide boards from cedar downed 100 years earlier. No such material exists today.

                  I've seen these boxes in the Bagley Write Museum and the BC Museum in Victoria and they are superbly made. Before the white man and steel came along the Haida and PNW Coast Indians (yeah, I know Native Americans or First Nation but the local Suquamish glare at you when you refer thus to them over the fireworks counter or the salmon stand.) Anyway, it's amazing the quality of the craftsmanshi attainable with shell, bone, and stone tools.

                  It aint the tools. Tools make it quicker not better.
                  Last edited by Forrest Addy; 09-05-2011, 02:49 PM.

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                  • #10
                    <snip>
                    Originally posted by 2ManyHobbies
                    In wood and some plastics, that would be two passes with a router.
                    A rotary tool would leave too wide a kerf and produce ugly "gaposis".

                    Chris

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                    • #11
                      I'd use the router and make two passes. One pass with a strait shaft to open up the groove, then the second pass with an inverted radius cutter to do the undercut. Use a fence with clamps on the end to make the cuts strait.
                      Andy

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                      • #12
                        My best guess is that after the cuts were made, the artesian soaked the wood in water or steamed it, then stretched it tight when bending the joints. Roy Underhill demonstrated this on one of his shows. He steamed the wood. With modern yellow glue the joint will swell on its own accord. Since the glue penetrates the wood fibers it will not shrink when it dries. Either way, wet or steamed wood is best for bending.

                        FYI, a very old wood workers trick for removing a dent is to lay a wet cloth on the work and heat it with a hot iron. When it dries it does not shrink back.

                        Chris

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                        • #13
                          Originally posted by Forrest Addy
                          I'm not sure what that joint is called. As was said you see it in Haida and Kwakiutl storage chests.
                          I'm fairly certain it's called a "Bent Miter".

                          CYA, I could be wrong.

                          Chris

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                          • #14
                            Originally posted by Forrest Addy
                            Can't make that joint with a rotary cutter. It has to be shaped. Do the math. A rotary cutter has to be twice as wide as the profile it cuts and add for the shank. The width from the tangent to the shoulder is r * pi / 4. Steam to bend.
                            If it's going to be bent anyway, what's to say one couldn't bend the squared shoulder section back out of the way, whilst milling the radiused portion?

                            If I were doing it in wood I'd probably do something like that. Or just produce the radiused end on a thinned down piece, then laminate the square shoulder section, with a thin extension, to build up to final thickness at the same time the bend was to be finalized. Paying attention to grain matching of course.

                            Or... what about just doing it with some careful band saw work?

                            There's no way it's going to be an invisible joint, at least when viewed on edge, due to long grain crossing end grain.
                            Last edited by lynnl; 09-05-2011, 02:33 PM.
                            Lynn (Huntsville, AL)

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                            • #15
                              Originally posted by lynnl
                              If it's going to be bent anyway, what's to say one couldn't bend the squared shoulder section back out of the way, whilst milling the radiused portion?

                              If I were doing it in wood I'd probably do something like that. Or just produce the radiused end on a thinned down piece, then laminate the square shoulder section, with a thin extension, to build up to final thickness at the same time the bend was to be finalized. Paying attention to grain matching of course.

                              Or... what about just doing it with some careful band saw work?

                              There's no way it's going to be an invisible joint, at least when viewed on edge, due to long grain crossing end grain.
                              Making this joint in wood is rather trivial but esthetically interesting. Doing it in metal, which is actually my objective, is mechanically challenging. It cannot be done with a conventional rotating cutter. It will require a broach or other linear cutter.

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