The DIY frame jig thread

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  • Messed about with my jig a bit tonight and thought we should have a thread for people to post their successes and failures and DIY jig building.

    This is what I started with,

    The uprights weren't very secure and went out of adjustment very easily. I think @biggles had this issue with his jig too.

    The bottom bracket also gets in the way of the mount for the seattube upright and the rear axle was the fixed point so if I set it up then wanted to adjust chainstay length it mean moving everything (and it inevitaby going out of adjustment as I moved it...) and because of the weight of the uprights I'd been horsing down on the bolts that hold the pivot blocks to the base and the t nuts had chewed up the channels in the extrusion a bit making adjusting it pretty difficult.

    All I'd had to make for that though was the pivots for the uprights (cuboidal blocks of ali drilled a few times and faced to be square on the lathe,'cones' for the head and seattubes which I just did stepped rather than tapered as the lathe I have access to has a terrible compound slide and the axle holder which was again just a drilled and faced block of ali.

    Cost of that jig was around £100 I think, main costs being 1x 1m length of 2080 and 2x 750mm lengths of 2060 extrusion.

    This is what I've come up with tonight,

    I can now adjust front and back end geometry independently and (I think) the frame will come in and out of the jig more easily now.

    Also added a little mount to the back so I can hold the jig in my workstand as well as the vice.

    This design uses only 1 of the 750mm bits of 2060 so would actually be cheaper than the original iteration.

    Who else has a home made jig to show off?

  • good work, it looks more thought out than the first one and arranged more like a pro jig.

    I have a pile of extrusion and some lathed up parts so far. nothing to be proud of yet

  • Are you using 20 series extrusion or bigger stuff?

    I think most of the hogs I’ve looked at use bigger stuff but there’s not so much available on eBay for the larger sizes.

  • I bought all my alu extrusions and bits from KJN. They are basically a copy of Bosch profiles and quality seems great.
    And it wasn't very expensive.

  • im not sure of the series as I bought it secondhand but its bigger than 20, I think 50mm section. its going to weigh about 30kg when done, a lot heavier than I ever expected. not a bad thing though.

  • https://www.instructables.com/id/A-simpl­e-bicycle-frame-jig/
    Stumbled on this whilst rambling thru the internet and thought it might provide some inspiration to DIY jig builders

  • There's a guy over on the not frame builders group banging on about something called a chop source jig reckons it goes for about 500 sheckels

  • It does but it’s like the bicycle academy one where you have to supply some metal tubing yourself, it’s a couple hundred $ for shipping and another couple hundred $ for the stand.

  • Well there you go more choice

  • I should have some 30mm Bosch-compatible profiles leaving Germany tomorrow (for a trailer rather than a jig, but >>>>) from motedis.co.uk who have a Worcester office, but do their processing in Germany. I couldn't find anywhere in the UK that sold cut lengths at a price competitive with them, and they do have lower prices for "standard lengths" (1980mm, 1000mm, 500mm) and bulk packs.

    They quote 3-6 days "ex-works": mine took 4 days to go through manufacturing/processing, but has taken a whole week to go through "packing and shipping" to get a message saying it's leaving tomorrow.

    I guess the real solution would be to buy a chop saw and sell lengths to subsidise my own needs.

  • Do you mind me asking what size profiles you're getting and a price? I am just pricing up right now, having bought the kit from Ideas 2 Cycles (thanks for the link, @Rik_Van_Looy). The kit cost 99 euros, and is on its way. I am thinking of building the jig out of larger extrusions to make it stiffer, but costs quickly get big with the larger profiles.
    I've been looking at extrusion prices on aluminium-profile.co.uk, they are about £11 per metre (40x40mm) or £19 per metre for 40x80mm.

    If anyone has any experience with this kind of jig, or thoughts on what I should look out for, I would be grateful!

  • Will the extrusion parallel to the seatpost be in the way when you are welding/brazing?

  • It might if I wanted to do full fillets in the jig but I’ll really just tack in the jig then remove the frame from it to do the fillets as this allows me to check alignment better I feel.

  • Yes. I guess an alternative would be to split that section and have two pieces going up and down at ninety degrees (or more) from your central extrusion.

  • The heat from brazing causes the tubes to expand and contract and as the heat is focused on one side at a time, this has the effect of pulling the tube one way, out of line.
    Apparently, since the jig holds it all together, the tube will pull but be held in place and when the fillets cool, you'll have built tensions into the frame which can cause cracking or failures in the future.
    Don't think any framebuilders will braze a full frame in a jig, just tack as M_V says.

    (This is what I have read, I don't have enough experience to say either way)

  • Point taken. Nonetheless it seems like better access is better, even if it's just for tacking.

    On the other hand I suppose the single section may simplify setting the seat tube angle.

  • Back in the early 90's when cheap lugged 501 frames were mass produced this was a common failure mode, e.g crack s between head tube lug and shifter boss.... Raleigh, falcon, Holdsworth etc brazed in jigs by factory workers

  • Interesting, I hadn't heard that before

  • That cheap Holdsworth I chopped up sprang like a fucking kangaroo when I cut through the seattube.

    To be honest though, I don't think I've ever cut up a frame (and I've cut up a few) that didn't twist at least a bit once given the opportunity.

  • Sounds about right.
    My bro had a headtube crack on an early 90's falcon team bike and took it to our framebuilder (Abilita) - he said that Reynolds lugged frames shouldn't be jigged during braze. He then showed us a pile of mass produced 501/531 with cracks around the HT/DT area .
    He said you get away with this technique on gas pipe but not fancy alloys or butted tubes

  • Hey @scarlet, have you had the chance to use the jig already? What profile did you end up with?
    I'm in two minds about sourcing the materials by myself and machining the parts at the local artsy space, or skipping this step altogether and getting the complete jig to begin with, learning basic machining later on if the whole framebuilding thing takes off.
    When it comes to buying a jig, price is too steep most of the times for me, but 100€ is really hard to beat in that regard, but also a little suspicious :/
    I read through the instructable a couple of times and didn't notice anything fundamentally wrong, but I've no clue.
    Do you have any feedback regarding that one? I'm looking for something to get a feel for it really, moving on to a more legit jig if I find this one limiting after having brazed a few frames.
    Any input would be helpful, cheers!

  • Bear in mind that for 100€, all you get it this:

    You still need to buy all the profiles and angles

  • I have heard about the frame stress caused by a ridged jig..in fact I remember Jason rourke saying his jig has a enough flex to cope with movement.
    Old school london frame builder Ron Cooper (now sadly passed away) did away with the jig completely for the same reason.

  • Right, I see now.
    Thanks for pointing this out!
    I'll then do more research on the jig designs if I ever decide to go with the kit.
    Having to source the extrusion separately it may as well make sense to build something else entirely.

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The DIY frame jig thread

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