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.