My frame building jig- Mtbr.com
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  1. #1
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    My frame building jig

    As per a few people on another thread, here is what i made.

    I made it primarily to make my first lugged steel road frame, so it was buit with that in mind. (but has since proven fine to make a full suspension, and kids bike as i built it a lot of adjustability.


    My rational was that i could use it to hold tubes in place for brazing/tacking, but also use it as a jig to help with tube mitreing. I wanted it so that i could quickly drop individual tubes in and out, to a repeatable position, to be able to quickly see if my mitres were correct.

    Also it obviously had to have the correct geometry, i figured 1 way of achieving this was to have the struts of the jig, mirror the actual tube locations and intersections.

    It's basically all made from 40mm aluminium uni-strut extrusion.
    The long bottom horizontal strut is actual wheel base, with slots cut into it that will except 10mm rod for front and rear axle. (even tho front is fairly uneccessary). Downtube strut and seat tube strut are milled to half thickness at the ends where they overlap, and an M8 rod joins them, this also extends so that i can screw 2 conical spacers on to it to hold the BB in place. I've got Tee nuts slid into the struts in various places, these then connect to the T-shirt shaped pieces of plate via M8 threaded bar to make V-blocks which hold the tubes.

    Head tube is is held in place by 2 short sections of extrusion mounted on 90 brackets, then another M8 threaded with 2 more conical spacers, this clamps in via Tee nuts. And 2 stops behind tee nuts so i can remove easily, and replace in exact same spot.

    Rear axle/drop outs are held in place via an M10 threaded rod, this has flats machined onto it to help locate in the 8mm grooves of the uni-strut, just a load of nuts, washers and spacers to replicate any axle width. Not pictured but there are 2 extra steel strips which slot over rear axle rod and BB threaded rod to gurantee squareness.

    To actually use it can lay it flat on its back on a surface table and set height of everything. I start by setting BB height(from table) and drop outs relative to this. Next i have a vee attachment in a height gauge this makes it easy to work to centre line of any diameter tube, and simply wind all my little T-shirt vee blocks up/down until it all matches. Finally I then set all lengths and angles of the frame on the fixture, and clamp it all tight. Now i don't need to measure individual tube lengths or mitre angles, i can simply drop tubes into my vee blocks and use the jig as a master.

    Sorry if that was rather long winded! I'm currently couch bound with a bad back and this is me filling time!!!!!

    More than happy for comments/criticism, this is my first attempt!

    My frame building jig-img_0061.jpgMy frame building jig-img_0066.jpgMy frame building jig-img_2152.jpgMy frame building jig-img_2271.jpgMy frame building jig-img_2292.jpgMy frame building jig-img_2299.jpgMy frame building jig-img_2958.jpgMy frame building jig-img_2983.jpgMy frame building jig-img_2996.jpgMy frame building jig-img_e0236.jpgMy frame building jig-img_e0047.jpgMy frame building jig-img_0063.jpg

  2. #2
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    Very nice. Thanks for the write up!!


    Sent from my iPhone using Tapatalk Pro

  3. #3
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    Awesome!

  4. #4
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    thanks for posting this!

  5. #5
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    More details on that kids bike you have loaded in the jig. Looks cool.

  6. #6
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    its an adult bike heavily chopped up to suit 20" wheels. Is that enough info? I can post up a thread and a million pictures if you are interested. It was a project for a friends son.

  7. #7
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    Always eager to see other people's projects. If you have a link to a gallery of pics that would work.

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