Brazing a bottom bracket at the Asylum

Building a bike frame from scratch

My 9 month experience building a bike I could call my own

Mike Swartz
6 min readAug 14, 2013

I pride myself as a builder of things. In my day job at Upstatement, I build websites. But in my daydreams, I think about building physical objects. I’ve built a few wooden tables and fabricated a couple steel pieces with MIG and TIG welds, but I wanted a project that would push me to learn more about metalworking and the metal shop itself.

So I chose to build a bicycle frame. I found a framebuilding class at the Artisan’s Aslyum, a local makerspace with all kinds of tools, materials and colorful characters to show you how to use them. This past winter I sketched, calculated, sanded, filed, melted, burned and sandblasted my way to a steel bicycle frame of my very own. Here’s how it went.

Planning the build

A diagram from Paterek. Doing the math was critical.

A bike frame is an object with specific performance parameters and tolerances. Unlike say, a table, where performance includes not falling down or tipping over, a bike frame is built to endure a lot of specific stress and convey its rider safe passage. Basically, I wanted to make a bike that not only fit me and accepted standard parts, but also didn’t kill me when I rode it. This involves a lot of planning, measuring, and calculating.

Our instructor Paul Carson pointed us towards the Paterek Manual, a classic handbook for the framebuilder. Based on your measurements and the type of bike you want, the manual will tell you what length of tubes you need and what the angles should be.

After plugging in my measurements (and realizing that my legs are freakishly long compared to my torso), I had a sheet full of scribbles and drawings. If I could get some steel, cut it to length, and somehow glue it together, this piece of paper said I would have a bike. So now I need some steel.

Skills unlocked: Planning, Trigonometry, SAE/Metric conversions, Patience

Gathering materials & prepping the parts

I knew what size bike I needed, but I wasn’t quite sure what style of bike it was going to be. A touring bike? A city commuter? A cyclocross/mountain-y thing? I considered all of these options, but had a few guiding principles. The bike needed to be:

  • Versatile. I want to be able to change it and bolt stuff on/off as my needs and whims change. Room for big tires, fenders, and lots of braze-ons for racks and things.
  • Stop-able. I knew I wanted Paul cantilever brakes, and basically planned the build around that. I like to be able to stop, especially in snow and rain.
  • Cool. I wanted the bike to be unique, and had a vision for it from the beginning. A simple flat black paint job with silver and gold parts. Not a knockout with flashiness, but a sleeper.
This is what a bike looks like before you add the blood and sweat

After a ton of research, I ordered a whole box of Columbus steel tubing from Nova cycles, along with assorted small parts like dropouts, rack bosses and cable guides.

Based on my measurements and the ideas in my head, I mitered the tubes on a small engine lathe. This was kind of nerve wracking to take a bunch of beautiful bicycle steel and cut, grind and file it to size. But the fit-up was pretty good, and I was on to the next stage.

Skills unlocked: Amazon Expert, Lathe Operations, Patience

Melting metal

This was by far the most fun, scary and rewarding part of the build. I decided to fillet-braze the bike, which means mastering the handling of the oxy-acetylene torch. If you’ve never seen one, it’s a pretty hardcore setup. One tank of oxygen, one tank of acetylene, a ridiculously flammable gas. This potent mixture can produce a flame that burns at around 6000 degrees Fahrenheit. It can also explode and kill you. So being careful is pretty key.

Before …
… and after. I bit off a big project with the slash-cut seat-stays, but it was fun
The frame and fork after brazing

The art of brazing involves heating the work to a temperature where a filler metal will melt and flow onto both pieces to be joined. You start to get a feel for how hot you need to get it. Especially when you’re dealing with really thin pieces (like dropouts) and thick, slowly heating parts like bottom brackets. The trick is getting the metal hot enough to push some melty filler-rod in and get it to bond, but not so hot that the steel starts to melt. It’s hard. And really really fun.

Once I tacked each piece of the frame together and assembled the fork and crown, I had a bike frame. It was covered in lumpy bronze and flux (a paste that keeps the melted metal from alloying with crap in the atmosphere), but it was definitely a bike. After a ton of filing and grinding, I was ready to get it painted and bolt some parts on.

Skills unlocked: Burning Stuff, Burning Myself, Filing x10, Patience

Putting it all together

Starting to get excited and hang some parts on the frame

It seems like the hardest part was picking all the parts that make a bike frame into a bike. I had three boxes from Amazon showing up every day for two weeks. Everything from spokes and rims to a headset and three-speed hub.

The actual build-up went pretty smooth, with the exception of having to use an angle-grinder to shorten my headtube at the very last minute, and having Paul cut off and re-braze my canti-bosses when we realized the jig was off by 40mm.

It took about three weeks to build the whole thing with the setbacks, parts that didn’t fit, and the wheel building. There were a few nights out in the garage where I was tempted to just rip through and finish the build if I had to stay up all night. But I decided to wait, and give myself some time to think about the problem or order the right part instead of scrounging/modifying what I had. I heard a great piece of advice from another guy at the workshop:

Whenever I think I’m 30 minutes away from finishing a project, I stop and come back to it the next day. This way I don’t rush, and force myself to be smart and do it right.

I think about this a lot and how useful it is when applied to basically everything. Don’t rush, do it right. You don’t want to ruin 9 months of work because the hardware store was closed.

Skills unlocked: more Patience

Riding the bike

The finished bike sitting outside the office.

Since the day I put the last bolt on back in May, I’ve put about 700 miles on the bike. It’s not the greatest bicycle around. It’s still got some lumps in the fillets, leans a little to the left, and a rack boss snapped off the other day.

But every time I ride it I think of what it represents. All the learning that went into it and all the great people I met along the way. Even if the bike eventually rusts away to nothing, it’s just the physical manifestation of an incredible journey that I get to keep forever.



Mike Swartz

Principal, Creative Director at Artist, guitarist, maker and breaker of things.