CNC milled bicycle frame jig

This bicycle frame jig is cut from MDF. It’s the latest in a growing trend that we love to see: the increasing availability of manufacturing techniques for the common hacker. This is a Kickstarter project, and alas it appears the designs are not available for you to cut your own. But we love the potential this shows, and maybe you can use the concept the next time you’re welding together a frame for something.

We really never look at building traditional frames at home. Mostly it’s the oddities that catch our eye. But if you’re into cycling and want to get your own custom-fit frame this has got to be the lowest-cost option available. In fact, you can get the jig and a tube set for under $600. The frame can be fit with just a few hand tools (a hack saw and a file). It uses lugs so the joints will be strong as long as you get the pipes fitting well enough for a quality welded joint.

22 thoughts on “CNC milled bicycle frame jig

  1. This is really cool but it shouldn’t be on Kickstarter.

    They aren’t looking to fund a project,they are trying to sell it.

    Plus,it’s not even opensource, Mr. Szczys,you should stress more that fact.

    This is more a product showcasing than a hack,I think despite the cool factor it shouldn’t be here,in that particular form.

  2. So… no one sees the problem of making a welding jig from something flammable? Also, I weld and I do not think MDF will be able to hold the tubes in place once you start welding. The amount of force that is generated via the expansion and contraction of heated and cooling of any metal is in the tons of PSI. This jig would have to made out of steel to work at all.

  3. It’s not a bad idea but unless you tig weld the frame spatter will eventually get the jig smoldering. More importantly MDF isn’t really strong enough to keep the frame from warping under the heat so you would have to jump around with your welds and use tig just to keep the heat to a minimum.

    1. Electronbee types faster than me, glad I’m not only one who welds. Forgot to mention the fact that among the things used to bind MDF together, formaldehyde is probably the worst. So while you get a warped bike, risk starting a fire, you also increase the chance of lung diseases/damage. I use a air filter &cyclone in the shop but still put a mask on just to cut MDF.

      1. The hackerspace I’m in has discussed the issue of the formaldehyde when dealing with our laser cutter. Apparently, there are some MDFs out there that don’t use it.

        As for the warping, that was the first thing I thought of with this. One way to avoid warping might be to just do tack welding at each joint on the jig and wait for everything to cool down between joints. Once everything is tacked into place, you could remove the whole frame from the jig and finish the welding. Of course, my welding experience is extremely limited to someone with more welding knowledge may be able to blow a hole right through my idea.

        As for lighting the jig on fire, you may be able to coat the jug in high-heat paint to avoid problems from sparks and there may be some kind of ceramic stand-offs that could be used where the MDF would, otherwise, come into contact with the hot frame.

  4. You vastly undersell the difficulty of frame building. I can see my frame building friends over at gnashing their teeth over this. Also, as has been pointed out; it is doubtful MDF could withstand the deformation the tubes go through when heated; so it is likely that the would be builder would end up with a crooked frame. Most frame builders make jigs out of aluminum extrusion.

    Still, it is a good idea and maybe it ever works! I’m even tempted by this one. I’m not sure why anyone objects to this particular kickstarter as the goal is modest enough. It’s a far more worthy project than yet another iPhone holder.

    – Robot

  5. I’ve done a little research on frame building and one common theme from professional builders is the need to cold set most joints after joining due to warp. This seems to be an accepted byproduct of joining with heat and is easily correctable using a little leverage. Another common tactic was to use the jig to tack the frame together and then finish the joining out of the jig.

    1. Seconding this, I’ve been watching far too much of the series “How it’s made” and even after multi-torch brazing in a metal jig cold-setting is usually required afterwards to get the dimensions just-so.

  6. Correct, you will probably have to true the frame after it is done regardless of the method. However, you want to do as little adjustment as possible and I think this MDF contraption will just make the frame more offset in one direction over the other. I think if one is serious about welding bike frames, investing in a piece of 3/8″ steel plate and then mounting, adjustable, steel posts, is a better buy in the long term. I just see so many other ways to make this that are better buys for the money.

  7. First: This is nowhere near the cheapest way to build a sweet bicycle frame. A piece of MDF with 2×2 (50mmx50mm)lumber screwed onto it and a few shims will do the job. Thanks to Henry James (bicycle lug maker extraordinaire) for this beginner’s tip. Add a tubeset for under $100 (again from HJ) and you’ve spent less than 1/4th the $600 quoted. This will get you started on a sweet butted CrMo frame, but you have to add the costs of BB, fork, dropouts, braze-ons, etc.

    With today’s metals, butted tubes, and construction techniques, lugs are essentially a fashion item, and do not make a frame appreciably stronger. But note that lugs are brazed, not welded! Regardless of the technique you use (lugs, fillet brazing, TIG, etc.) practice before you build a bicycle that someone will actually ride.

    Regarding movement when welding/brazing. Typical hand builders either pin or tack the frame, then move it to a stand for better access when forming fillets, filling lugs, etc. The jig is not used for support during this process. The frame I built this way (lugged BB, fillet brazed elsewhere, set up on a piece of melamine coated particle board) ended up perfect, requiring no cold alignment at all.

    Building a bike frame is a moderately complicated undertaking. Rewarding if you get it right, but a lot of people will be better off taking a class from a pro.

  8. For a second I thought you meant a CNC milled cycle frame.

    That I would like to see. And no messing about with starting from a sand cast. I want to see it machined from one giant hunk of depleted uranium for downhill speed.

  9. How many frames are people planning on building? Going to the effort of making a jig for 1 or 2 frames seems overkill! Doubly so if previous comments regarding MDF’s durability are accurate.

    As always with space frames, tack then seem or you’re asking for heat warping trouble!

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