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  1. #1
    mtbr member
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    another question for u garage hacks

    (And I use that term with highest regards)....
    After a bit of a lay off I'm about ready to get restarted again. I have no fancy tools (files, hacksaws and vblocks) but pieces to cobble different things together that might be jig-like (tig btw)
    Can't for the life of me figure out a reasonably consistant way to get the right miter to the CS for the BB without hole saws and a machine.
    Any help would be awsome.
    Thanks

  2. #2
    The cat's name is jake
    Reputation: BungedUP's Avatar
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    What process do you use now, and what are the errors/difficulties in the process? Length, shape, angles, etc.

    I have machines and tooling I've made to specifically make this easy, so I'm just spitballing some ideas, without having specifically tried them.

    To get consistent length of each chainstay, if being filed separate from each other, I might take a piece of coat hanger or wire, bend it at one end to form a hook, then cut it to the length I wanted for the inside edge of the cope. I could use that to get a reasonably similar length without fussing about with a tape measure. I'd hook the coathanger on the axle slot, then use the other end to mark (assuming the dropouts were already attached to the chainstays). Once I knew that distance, I'd add the distance the ears of the cut protrude beyond the inside edge, then cut that length as exactly as I could. Then I might take a round dowel, attach it vertically to a piece of wood to form a stop for the end of the chainstay, and use that along with a compass to draw the correct miter shape, so that it just touches my inside mark (I'm not sure if I described that very well). Then I'd just hack aways at it, test the fit, mark areas that needed touching up, and continue. Just an idea if I had to do it by hand.

    Another consideration, if you have an air compressor, is to buy a pneumatic die grinder, and get a sanding sleeve and rubber drum, about 1" in diameter. With practice, those can become an easier way to grind in, and touch up your chainstay/BB cope.

  3. #3
    J_K
    J_K is offline
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    This is how I do the CS to the BB miter.

    First you need to find the CS to the BB angle, digital angle finder is useful here.
    Then I make a quick 3D drawing to make the miter template


    Next step is to find out the centerline of the chainstay


    Then do the filing


  4. #4
    WIGGLER
    Reputation: todwil's Avatar
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    Another consideration, if you have an air compressor, is to buy a pneumatic die grinder, and get a sanding sleeve and rubber drum, about 1" in diameter. With practice, those can become an easier way to grind in, and touch up your chainstay/BB cope.[/QUOTE]


    This is how I do it, as long as the CS/ST are the same length before sanding they will be so close that most wont be able to tell you made them one at a time.
    PAYASO 36er.....Live the Circus

  5. #5
    The cat's name is jake
    Reputation: BungedUP's Avatar
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    I like J K's method, assuming that one has access to the necessary 3D software. The addition of the centerline as a reference for taping on the template makes it thumbs up.

  6. #6
    J_K
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    Quote Originally Posted by BungedUP View Post
    I like J K's method, assuming that one has access to the necessary 3D software. The addition of the centerline as a reference for taping on the template makes it thumbs up.
    I'm using trial version of the Rhino Ceros 3D software, it's quite easy to use and is fully functional (except the clipboard) and will save 25 times. You can live with the saving limit, once you have the basic design you just make changes for it without saving it once done.

  7. #7
    Harrumph
    Reputation: G-reg's Avatar
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    Nova's tubing notcher

    Or pony up for BikeCad Pro and use the mitre template function, this is what I do in combination a home made jig.

    The real work is still done in the jig by slowly hand filing things, but the mitre templates help to keep things in phase and get pretty close to the final cut.
    Slowly slipping to retrogrouchyness

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