I've been wanting to design and build a frame for a long time. I'm 6'7" so I have never been on a bike that
truly fits me and my toes constantly smash into the wheel whenever I turn. Frame design is essentially 1,000 decisions made correctly,
to serve the overall purpose of the bike.
My badass grandpa very generously offered to bring me along to a 3-week frame building class with the legendary
Doug Fattic. He's been teaching people to build steel
frames in the English tradition for over 40 years. The class is a constant exercise in best practices and zero shortcuts.
The goal of the class is that we'll be able to make more frames in the future without handholding.
This is the current state of the bike. It needs to be painted and I need to add things like wheels.
Doug's shop is on a nice green plot of land in Niles, MI. We stayed next door in a house he rents to students.
Class runs 6 days a week from 9–6. We had shop access in the evenings to do lots and lots of filing.
I rode on an adjustable fitting bike to get the hard points located properly. Butt, pedals, hands.
This frame was designed to be a sturdy single-speed monster. I'll use it for short rides around town.
It has an upright riding posture because I'm not trying to hurt my neck for a 5% aerodynamics boost the 5% of the time I'm going over
20mph. It will be able to handle curbs, potholes, dirt, and my size. It's not a race bike. It is lugged steel. There are a million
reasons to choose steel over carbon fiber, aluminum, or titanium.
We then used dummy parts to convert the CAD drawing to Doug's custom fixture.
Laser cut and etched steel and hundreds of little parts to hold it all together.
We decided to start with blank lugs. I did the design in Illustrator with a template Doug provided, and used
rubber cement to stick the patterns to the lugs. Packing tape on top to prevent the paper from wearing away.
I used a Dremel for rough cuts. The lug is held in a specialized lug vise, which expands inside the tube to keep it steady.
These are some of the files Doug has. I got to know these very well.
At this point, I thought I was done. The goal is to get a perfectly uniform surface on the "shoreline" of the lug,
which will be perpendicular to the tube, always pointing to its center. Doug is difficult to impress—he knows students aren't
capable of making master-level work but doesn't want trash leaving his shop, either. A quick glace at filed lugs with a practiced
eye reveals a lot about the skills of a frame builder.
I drilled the holes small so I could file them into the proper position when I inevitably did them wrong. Smart!
That took a couple hours. Small files don't remove much material. Drill your holes right the first time!
All the cast parts have kind of gummy, rounded shorelines.
It's important to crisp them up. This is one of the many things other frame building classes won't teach you. It's
personal choice whether you decide to uphold traditional standards of quality, but it's what Doug teaches.
Cast parts also have a fine sand texture that can be filed off for better texture later. This way, you aren't relying
on primer to make a smooth texture.
You can file these things when they're on the frame, but some tight areas could be more difficult to reach.
Lugs done. Since I have two top tubes, I got to do two extra lugs.
Next, we learned to braze. That's the badass grandpa I mentioned.
It turns out you can use a medical oxygen concentrator and plain ol' propane. This saves the expense and hassle of buying
expensive oxygen and acetylene tanks.
The purple glasses aren't necessary, but they eliminate a yellow flare so you can see easier.
On the third day, we started interacting with real bike tubes! Starting with the seat tube and the bottom bracket shell.
When you miter tubes together, you just use a hole saw that's the size of the tube it's fitting against or the space it has
to leave. A bottom bracket is about 1.375" in diameter.
I also removed the material for the down tube, otherwise it would be in the way.
The bit that's showing gets filed away after the first braze is done.
The touching faces of the joint are cleaned with emory paper. You make lengthwise gouges to facilitate better silver flow.
All lathered up with flux. The flux protects the metal, melts, and allows silver to flow in the joint.
Every joint gets a spot of silver to keep it in place. A flat table is used to make sure everything is aligned. After alignment
is confirmed, a second spot is added on the reverse side to keep the tube from twisting.
Every time heat is added to the joint, the frame needs to be re-aligned. By correcting small errors as they occur, you can
eliminate the need to correct a stiff frame that's 5mm out of alignment once everything is brazed together.
My first real braze is done. I did the work of each braze, and can confidently say I can make a bike that won't fall apart.
Doug, or his assistant Herbie, was always present to go over the shorelines of each joint with the flame to make sure everything looked super
clean. That's the only way to get a pretty bike while you're still learning to braze.
Silver flux is water soluble, so warm water for 15 minutes after each braze is done dissolves it all.
If you look closely, you can see silver has come through the joint. It's more difficult to tell when it's covered in flux and
you're trying to figure out if the joint is completely solid.
The joint is sandblasted and needs to be faced. The drive-side face of the bottom bracket is used as the reference surface to align
the rest of the frame. This tool taps the threads and makes the two faces flat and parallel.
This assembly keeps the bike elevated and parallel to the flat table.
A surface gauge is used at each end of each tube to ensure it's parallel. If it's not, you just push or pull.
This is used to determine where the tubes change thickness. Bike tubes are butted at each end, so the walls are thicker
at the joints for strength while the middle section is thinner for weight savings. I'm using .9-.6-.9mm thick tubes.
Two top tubes mitered to the head tube.
Custom v-blocks fit into the fixture to hold things steady and flat.
Balancing the length of thicker tubing at each end of the tube is one of the many decisions you make when you're building.
Yet another reason this bike is heavy is the fact that the tubes are long, meaning very little of the thicker portion was mitered away.
The lugs need to be a nice close slip fit. Silver needs about .002"-.004" to flow. Too much and it won't fill the joint.
Holes where the top tubes meet the head tube allow for airflow. Otherwise air tries to escape the joint you're trying
to fill with silver.
A thin film of flux on touching surfaces before spot brazes.
This lug didn't have much to grip onto, so I used a little clamp to keep it tight.
The whole thing is spotted together, and needs to be realigned. The second top tube goes on later, so it's easier for me to file
the lower set of lugs.
That's what too much silver looks like. The extra tube is used as a "dumping ground" and heat sink, since it will be removed
later, so it's OK that the silver piled up there. The visible shoreline is crisp.
If you chopped off the top parallelogram it would be a normal sized bike.
The lugs need to be filed to remove imperfections and take them down to a uniform thickness. This is where you can tell a
high-quality custom frame from a production one. The best traditional framebuilders have paper-thin lugs that are entirely uniform.
Marks on the tubing surrounding the lug are a sign of a rookie still learning to use files properly.
Finer and finer files followed by emory paper. This takes hours.
This is my grandpa at the same stage. He's better at filing. His lugs have a more ornate design, but still classy and simple.
Custom wood blocks with holes of different diameters let you put a frame in a vise at a variety of angles without
messing up the tube.
Using flat and square things to get the seatpost binder bolt lined up.
Fillet brazed into place. There's some porosity but it's pretty clean for my first one.
Forged lugs are pretty gummy looking so it's good practice to file the outer faces to be perpendicular to one another.
Doug does it all by hand. I used a belt sander. I could see how easy it would be to sand too far.
Chainstays are dry-fit into the sockets to roughly position the dropouts parallel to each other with an axle. This doesn't
need to be very accurate since they can be so easily bent around later.
You have to add way too much brass to fill the joint, so you can file it back later into nice scoops.
Filed into a scoop on the outside, a bevel on the inside. Bevels are for rear cog clearance, and I did them even though
my bike is a single speed because I like the somewhat traditional look. I chose a very gentle bevel and feathered it into the tube.
Half-round files are made with a specific descending series of diameters so it's easier to hand-miter a tube. This is
The tubes start as round, but it's common to squish them in a vise so they're ovalized in the middle for tire clearance.
This is a bad photo of a T-shaped fixture that simulates the seat stays, holding the chainstays in the proper position.
My class manual is filled with rushed drawings of such devices. Herbie made this one, and I'd have to replicate it if I wanted
to make the rear triangle in the same way in the future. There are expensive premade fixtures out there.
Silver drips into the threads of the bottom bracket so it needs to be re-faced and tapped.
This is my favorite thing in the shop, the Campagnolo H tool. It's two pieces, each of which attaches to a dropout or fork end.
Each piece has a cup, and the goal is to align them. You bend the dropouts so the cups are perfectly aligned, as shown here.
Everything's aligned. That's tested by putting a true wheel in the dropouts and measuring each side to check that it's in line.
Time to assemble the rear seat stays! I'm using a beautiful wishbone cast part. I brazed the top stay in because it already
fit perfectly, and it can be cut down later.
This is a fork building fixture but it works just fine for assembling the seat stays. The first time I tried to build this, the
stays were spread too far apart. I used a fork blade bender to pull them just a little closer, but the tool turned the round tube into a square.
Oops. It was a $50 mistake since I had to order new tubes.
You braze the joints in the fixture.
My next mistake was cutting the stays 8mm too short by measuring from the wrong location. Luckily, I had the old stays that I had
messed up, so I was able to create a little extension.
Doug did these brazes—it's harder than it looks to get the metal just the right temperature.
Once it's filed down, the difference is undetectable!
I used a scrap tube to make a 1" collet for holding the tapered stay in the machine vise.
I used a protractor to find the approximate angle of the stays for a hand miter.
The dropout tabs needed to be filed so the stay ends would fit properly.
My hand mitering got us close and allowed for a position check.
This milling setup took over an hour. It's important that the mitered fit is perfect. Slop makes brazing more difficult.
I hand-bent the chain stays so they would be applying pressure on the joint, and used heavy blocks to keep the miter in
As the frame gets more oils on the inside, each braze creates more smoke.
Herbie did this braze since it's a little do advanced for me to do confidently without messing something up. Brass melts
at a higher temperature than silver, so the underlying joint is always in danger of being messed up somehow. He did a great job, and I filed
it so that it would be perfectly round.
A hole needs to be poked in the tube so gases will escape from there rather than the hole you're trying to fill with brass.
It's filled with a tiny scrap brass rod...
That's the main frame geometry completed.
The seat tube needs to be reamed.
Two hacksaw blades side by side create a perfect width of slot for the binder bolt to clamp around the seat post. They separated
for one stroke of the saw, and gouged the sides of the binder bolt a little. Disappointing, but hardly noticeable.
Tiny little rounds. The bottom of the slot gets a U, also.
Adding a chamfer to the inside of the slit so that it doesn't mar the seat tube by pinching.
This is a hone, typically used for engine cylinders. It just makes everything nice and smooth.
This tool reams the first half inch and faces the head tube.
I love being able to see the little layers.
Onto the fork! I chose these decorative lug-style ends to match my lug ornamentation.
Steerer into fork, and excess filed away.
These are thick, sturdy blades.
This is the fork blade bending tool, or "seat stay ruiner" as I have dubbed it.
You just push a little harder every time until you achieve the rake you're looking for.
Sandblasted. You can see a tiny silver ring at the joint. Pretty cool.
The fork crown tips need to be tapped into place to make the smallest possible gap between the cast part and tube. Silver can't
fill that gap, and besides, to quote Doug: "It would be butt ugly."
This braze is a little tricky because you can't see how much silver you're adding to the joint. You just have to make sure
your heat pattern is pulling silver in.
The fork building fixture has mechanisms to ensure that the rake is correct. In my case it's 50mm. The hole is for air escape,
and I positioned it in the ornamental hole, which happens to be about the same size as a water bottle boss. That way, I can use that threaded
insert as a mounting point for future fenders. Again, I drilled the holes badly and had to file them into the right position before enlarging.
Steel tubes are squirrely!
I could mirror this one so it would match the others but that would be dishonest.
I filed away the flange so it's pretty tough to tell there's a threaded insert there at all.
Facing and externally reaming the fork crown race.
Alignment completes the fork.
These are all the little gubbins to braze onto the frame. Not pictured are water bottle bosses.
Getting the brake cable guide post at the right height.
Some clever fixturing to get it in position.
Scrap tubing of the right size—an optical judgment—is drilled and hand mitered to fit for a bridge. This adds
stiffness, which I do not need, and provides a place for fender attachment, which I may need.
A water bottle boss finishes it.
These clamps are designed to hold slotted cable guides. Pretty cool.
These are stainless. At some bike schools this is the first braze you ever try, but I did them last.
Doug would never use a dremel to clean up spilled silver because he would never spill giant globs of it on his bottom bracket.
The sandblaster could fit a tandem bike. Comfortably.
You can see a pinhole in the silver on the top of this lug. That happened because the heat added to the joint when fillet
brazing the top stay sucked silver inside. You can either re-heat the joint to add more silver, or use spot putty later.
There are a few little places to fill, but I'm very happy with the frame. Soon it'll be painted and rideable!