The simplest bicycle framebuilding jig I could come up with...

Picture of The simplest bicycle framebuilding jig I could come up with...
Here's a jig for building bicycle frames. This design is something I've been slowly picking away at for several years. Being both a cheapskate and not having much in the terms of machine tools and/or skills to use them, I've slowly come up with this design.

It's based off the easily available 8020 extrusion, and repurposes a lot of the 8020 small parts. I've tried to make every part requires as little machining as possible. In many cases, I've designed individual parts so that they can be initially made with as little tooling as a drill press, and slowly replaced with nicer machined parts as time/money/tooling allows.

If you want to machine all the parts yourself, you will need a small lathe (a 6" mini lathe is big enough) with a four-jaw chuck and a milling machine (or a milling attachment for the lathe) to make some of the parts. All the machining is simple and would make good practice in a community college machining class, if you don't have the machinery. If you do have to take it to a machine shop, it shouldn't be too expensive.

This Instructable doesn't give exact dimensions or step-by-step instructions. I've left it slightly vague to encourage the builder to customize it. If you want to build BMX frame or XXL 29ers you might want to change the overall dimensions. I've also some included some fancier or alternate parts to consider, if you want to make a nicer jig, practice your machining, or just have an easier time spending money than I do.

In case you're wondering, I don't have plans for sale at the moment. However, if you like the design, you can show your appreciation at my Amazon Wish List. If you get stuck on a part let me know in the comments and I could post more detailed plans. I have some parts drawn in Autocad.

This design and accompanying directions are licensed under the Creative Commons Attribution/Share-alike license. That means you can do anything you want with this design, as long as you give me credit, and allow derivative works to share this license. If you want to machine parts for this design and sell them, go for it. Heck, if you want to build full jigs and sell them, that's fine with me. Just give credit, and maybe buy me a beer if we ever meet. If you do make and sell new and improved parts for this design, I'd love it if you could send me one of your parts too.
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Tman19653 months ago

For the cones a Half Conical Coupler for lighting truss should do the trick. Tey are less then 10$ per piece and come in different sizes F33 should have about 40mm max diameter and F23 about 27.

jastilix2 years ago
Just curious if you've had any more mental revisions to the jig since you've created the guide almost 5 years ago. What comes to mind is the torsional stifness of the 8020 and to what extent one can assume that the surface is flat with just bolting it together over relatively long distances. Since the plane remains, the error seems shared and probably within tolerances. Comments on repeated or potential alignment issues you've seen come from the design? (DocW and others) Nice writeup!
drwelby (author)  jastilix2 years ago
Well, after 5 years of use I haven't run into anything that suggests the 8020 doesn't provide enough accuracy. You will have WAY more accuracy problems with your joining technique and sequences.
I haven't changed anything on the jig. I did add a simple seatstay holder and wondered why I didn't do it sooner. I also built a simple stand on casters - while clamping it in a Park stand is clever, it's a little bouncy.
Given the chance to build it again, I'd use the 1530L extrusion to make it lighter, and I'd make it a couple inches taller to handle long travel 29ers.
What else - seeing many other 8020 jigs pop up, I'm surprised I don't see more that use the angle bracket as an angle indicator at the top of the beam. I always thought that was super clever, but maybe it's not clear?
yangoose2 years ago
Maybe you have addressed this but how do you get the seat post to be on the centerline of the bottom bracket. The #4304 is 2" or 50.8mm. If thecenter of cone is anywhere other than the edge of the #4303 it will be off center.
drwelby (author)  yangoose2 years ago
The #4304 is 3" on a side, which should be obvious since it matches up to the 1530 extrusion.
Sorry, How silly of me.
bamboodood3 years ago
Hello drwelby,

great design! I just wanted to ask a question. How long should the button head bolts be? Are they all the same length? Thank you for your time

drwelby (author)  bamboodood3 years ago
16mm M8's
jimn6 years ago
Hi, Maybe this is a dumb question, but how do you hold the unwelded frame tubes in place? Isn't that one of the primary jobs of a frame jig? Thanks for your response and sorry if the question seems snarky -- it is an honest question! Jim
ragus6 jimn6 years ago
You tack weld...
jimn ragus66 years ago
Ragus6, I got that, but if you're building a lugless frame, you still need to hold the tubes in place as you tack weld.
I think the fixture holds some of the tubes (e.g. the seatpost) and the reminder are held in place via friction.

So you get the seatpost in place, you get the head tube in place, leaving it a tad loose, and then you cut and grind and machine the top tube until it fits perfect. then slide the head tube over a tad to hold it via friction.

When everything is in place, I guess a few tack welds or a bit of braze would let you take the frame out of the fixture and then weld everything 360.
drwelby (author)  jimn6 years ago
The only tube that needs to be held in place is the top tube, though often friction will hold it in place. If not I use a small clamp under the tube to keep it from sliding downwards. I have designed some tube supports for the top tube and seatstays and I'll add them to the instructable soon.
ragus6 jimn6 years ago
The jigs main purpose is to keep your HT angle and ST angle. If your copes are tight enough the jig should hold everything. (on the front of the frame)Check all your tubes in the jig then tack it up. (One tube at a time)
CementTruck3 years ago
This is a really great idea.

8020 is awesome! Tinkertoy/Lego/KNEX/Erector for grownups.
Awesome, i am going to build a series of L.W.B Cycles and this frame building jig of yours will be really helpful.
will post pictures here when i am done doing it.

once again bravo.
drwelby (author)  Bilal Bin Siraj3 years ago
Thanks! Look forward to seeing your bikes.
davmaldo3 years ago
So how come you put the head tube and seat tube holders at an angle? Since they're parallel to one another, wouldn't it have been easier to just make the whole thing square (i mean everything at right angles, i realize the jig is rectangular).
drwelby (author)  davmaldo3 years ago
I've played with designs that have a fixed seat tube and you just set the head tube at the difference between the head and seat tube angles - there's actually a picture of one in my other jig Instructable. However, I prefer to keep everything aligned with the XY system i'm used to, especially for stuff that's measured horizontally or vertically like top tube length, bottom bracket drop, standover, etc.

Also if my main jig is level, then I can measure tube angles with a digital angle finder.
Point well taken. I am in the design phase of a jig that i'm going to use to build a bamboo fixie. since i'm going to take an existing frame, chop it up, and replace the top tube, seat tube, down tube, & stays with bamboo, there is less need for those type of measurements as there are with actual bike fabrication.

on a different note, since i don't have access to a machine shop (or rather, i'm trying to keep things relatively inexpensive), I thought spheres might be just as good as fabricated cones for the seat tube, head tube, and BB brackets. To that end, i thought a few of these might get the job done:

only 8 bucks a pop, free shipping, no fabrication, and they already come with a tapped hole!
drwelby (author)  davmaldo3 years ago
Those could work for a bamboo bike. I've also heard of people using tow hitch balls and shower nozzles.
Also, what would you say you spent on all the 80/20 extrusion and hardware?
drwelby (author)  davmaldo3 years ago
$200 or so.
mcflorry4 years ago
this is an awesome frame jig! Thanks for the inspiration :D just one thing,what length did you make these angle beams?
drwelby (author)  mcflorry4 years ago
I think they're around 55 inches. You might want them taller if you're building frames for longer travel forks.
bikerusl4 years ago
Thanks, that's so awesome. I helped make a fork fixture using your guide as inspiration. It was so much better than the old jig (mode from MDF and scrap steel) I tacked up 3 forks in about an hour and usually it would have taken that long for 1.
nameofdane4 years ago
How does the jig react to the heat from welding or brazing? Any problems with distortion or with splatter damaging the jig? Excuse me if this was addressed in the 'able, but its been a while since I read through the whole thing.

Thanks for putting this together, I look forward to putting one together.
drwelby (author)  nameofdane4 years ago
Well, you should only tack in the jig so it's not going to get all that hot or exposed to damage. Plus it has a lot of mass and surface area to keep it cool.

On a technical level, as an extrusion the aluminum will distort in more unpredictable ways than mic 6 aluminum tooling plate when it is heated. But if you're that concerned about accuracy., you shouldn't be making this jig.

bpvh5 years ago
Do you have a parts list for this jig? I want to make sure I get everything I need from the 8020 distributor. Thanks
ahford5 years ago
I wonder if there's a nice way to mount a spare set of external bottom bracket cups to fix the BB shell via the threads? That could be a good no-machining way to fix the shell via the threads if there's a good way to mount them parallel and spaced out a little.
ajf3425 years ago
How wide did you make the recesses for the drop outs?
drwelby (author)  ajf3425 years ago
I made them 3/8" wide.
Spency5 years ago
Could this setup be used for a track bike? I'm just starting and I was curious. If this current setup can't be used to make a track frame how would you alter it?
drwelby (author)  Spency5 years ago
It will work fine for track frames.
Great job, nice jig, i'm just going to have to build a similar one now!
jimgskoop6 years ago
If making a cone on a lathe is difficult, could you use a BALL shape instead? Something like a small trailer-hitch ball? See this or this.
drwelby (author)  jimgskoop6 years ago
yojimg- I don't see why it wouldn't work. I'm not sure how round and on center those ball hitches are, but I'd think they'd be close enough to get someone started on their first couple of frames. Good idea!
might want to try out some harbor freight plumb bobs....6 bucks a pop, chop the fat end off then thread into it. not sure if they have a large enough diameter but they come in all sizes.....
srice5 years ago
Hi - great looking jig. I am looking at building one and I a confused by the attachment of the seat tube beam to the bottom rail. It looks like it pivots on a single bolt. Can this bolt slide along the bottom rail? If it can slide, how do you set the chainstay length?
drwelby (author)  srice5 years ago
Yes, there is an allen bolt inside of the cavity of the seat tube beam extrusion, and it mates to a T-nut inside of the top slot of the lower frame rail. You access the bolt through the hole that you thread the bottom-bracket hold-down into. So yes, as you asked below, the center of the BB, the BB mount, and the allen bolt and T-nut are all concentric, and the T-nut rides in the center of the top slot of the lower rail. To set the chainstay length, first set the BB drop by moving the dummy axle up and down. Then loosen the allen bolt inside of the seat tube beam and slide the beam along the lower rail, until the distance from the center of the BB mount to the dummy axle is correct.
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