Here it is, the time has finally come…
It’s time to build SB6398. The end result of this build will be a bike that is 100% original, exactly the same as when it left the work stand of Denton Cycles back in 1984. It will only be the slight patina to the paint and parts that may give its age away.
I want the series of blog posts for this build to be comprehensive, so these posts will be long and detailed, so be warned and be prepared for that!
Every frame is different but every build should start the same way, with frame prep! Good frame prep is the key to an excellent build. It is so tempting to get a build underway and start bolting bits to a bike, but prep is essential. The amount of prep and the number of stages of prep will differ depending on what you are working on. SB6398 only requires a light restore. If you stood back and looked at this frame you would think this frame was relatively new. It is only when you get up close and look at the tube surfaces that you see the patina and age.
To prep a frame you need to consider at least three things, sometimes more. On this build, it is the inside of the tubes (bare steel), the outside of the tubes (paint and corrosion) and the surfaces and threads that are to receive the parts. Other builds may require work on frame transfers or even frame alignment work.
Inside frame tubes
I generally start with this because it can get messy, the bare steel on the inside of each frame tube, blade and stay should be coated. I use BOESHIELD *Developed by the Boeing Corporation no less!.
Frame builders dealt with vent holes in different ways. When I built my frame last year, I sealed the vent holes once the frame was built, others leave them open. Vent holes are required in certain tubes to allow the hot expanding air inside a tube to escape during brazing and to allow air back in after the brazing is complete and the tube cools. If you don’t have vent holes expanding hot air inside the tube can blow brass back at you, or suck brass from the joint during the cool down leaving pin holes in the join. The tubes that require vent holes are…
- Fork blades – they become sealed tubes when the blade and dropout sub assembly are fitted to the crown
- Top Tube – this tube becomes sealed when lugs are fitted to each end
- Seat stays – these become sealed tubes when they are brazed to the rear dropouts
- Chain stay bridge – this becomes a sealed tube when it is fitted between the stays
The seat tube, down tube and chain stays all vent naturally through the BB shell.
Frame saver can be sprayed inside the seat and down tube and chain stays easily – the head tube and fork steerer are the same. Spray around the tubes and try and get good coverage but be prepared for it to drip quickly through the open BB. Most frame saver aerosols come with a straw type tube that can fit into the vent holes of the other tubes. You cannot see how well you are coating the inside of these sealed tubes so use plenty then leave the frame saver to dry with a rag under the BB to soak up the excess. Once it is dry, you should feel a waxy coating on the inside of the tubes – this wax forms a protective barrier and provides the protection to the steel tube.
Have you ever noticed a rattle in the top tube of a steel frame? Turn the frame up and down, does it sound like something rolling around inside the top tube? This is usually debris from the brazing process. Debris like this will fall out of the seat tube, down tube and chain stays through the open bottom bracket shell but unless you have unusually large vent holes in the top tube lug areas, this debris is never going to come out.
Super glue is ideal for this task. Squeeze a tiny dribble of glue into the vent hole and turn the frame over and allow the debris to fall into the glue, give it a minute and check for rattles.
PS, I don’t like my voice on video but had to record it so you didn’t think I just turned the volume down!
Paint and corrosion
There is no right or wrong way to do this. Each restorer will probably have their own methods. I start the task with a clean down of the paint to get the dirt off. I don’t pick at any loose paint or scratch at any corrosion, I just remove as much dirt as I can.
Next comes a paint restorer or cutting compound. Although it is often called paint restorer, I don’t normally use this to restore paint, I use it to get rid of the last of the dirt, that deep ingrained dirt sitting in cuts and scratches. The compound will also remove any loose paint or rust and give a firm, clean key to the next step, the polish.
Any areas of corrosion can be treated with rust remover. Most work in the same way, paint it onto the affected area and let it do its thing. It should chemically treat the rust, allowing you to apply paint back on top of good metal. Rust remover will turn the treated metal black which is ideal on the black frame I’m working on.
Use a good quality soft, clean cloth and rub the polish into the tubes. I then leave it for a little while and rub off with another clean cloth.
My frame is now rattle free, protected internally with a waxy coating and has gleaming paint following a good clean, cut and polish. It’s not perfect, that isn’t my aim, my aim is to preserve originality. That is step one and two of my three step frame prep completed.
Next up is prepping the frame threads, reaming the seat tube and facing the head tube and BB shell. Any work with thread taps or cutting tools should only be done with good amounts of cutting fluid. Cutting fluid not only lubricates the cutting tool and allows the cutter to cut smoothly, the fluid also protects the expensive and sharp tools. If you invest in these tools, you want to do your best to make them last!
Anyone can bolt bits onto a frame, that part isn’t difficult, it is just a few nuts and bolts. But prep is essential. You wouldn’t start cementing bricks together to build a wall without first prepping the foundations. A wall is no good without these firm foundations. Good foundations ensure that the wall is built on a perfectly level base. This is the same with a bike build.
The headset and bottom bracket bearings require two parallel surfaces – this allows the bearing that attaches to each side of a tube to run smoothly without any pinching or play as the bearing rotates. Hand built frames like any SBDU frame are faced during the actual frame build. Head tubes are left slightly long during the build and are then trimmed and faced either on a lathe or by hand, using a facing tool. This is my own frame on the lathe having the head tube cut and faced.
Two cutting operations are happening here. The face of each end of the tube is cut parallel to the other while the internal size of the tube is cut to the correct size to accept the press fit head set cups. One operation delivers both cuts.
Some builders will paint the frame and face the frame again to remove the layer of paint that has subsequently covered the clean edge of the tube. If it isn’t faced again by the frame builder then whoever takes on the task of building the bike should carry out this second facing process to remove the paint.
SB6398 has clearly been faced in the past but there is just a touch of paint present on the edge which I’m going to remove. The ideal outcome of facing is to have a perfectly clean, bare metal surface.
Facing tools work by facing one surface at a time. A cutter is placed in one side of the tube and is centralised (to maintain a parallel cut) by a self centering cone located in the opposite side of the tube. A spring is then tensioned to keep the cutting teeth in contact with the tube face to maintain a smooth cut. If the spring tension is too weak then the cutter will bounce and not cut cleanly… if the tension is too much then the cutter will bind and not cut smoothly. As you cut and face, the tension should be checked and adjusted to maintain just the right amount of tension.
Facing tools like this should always be used in the ‘cutting’ direction and never turned back on its self. Always remove the facing tool by turning in the direction of the cut and lifting at the same time.
The head tube is now done and looks so much cleaner. Both ends have been done to create two parallel surfaces. The facing cut has left clean metal and the cutting tool also cuts a slight chamfer into the tube face.
Bottom bracket shells are slightly different. The BB shell should be faced to provide the parallel bearing surfaces and the BB threads need to be cleaned (tapped) to allow the bearing cups to thread easily into the frame. However, these two operations can’t be done at the same time or even with the same tool.
I start by cleaning the threads with one tool and then face the BB edges with a second tool.
Using plenty of cutting fluid, turn the cutter into the threads and then remove. Cleaning the threads first allows the facing tool guides to be screwed into the frame. As you can see, the face of the BB is ok, but could be better.
The Cinelli bottom bracket shell is now ready to receive the Campagnolo BB – the threads and shell face are perfect.
Not to be overlooked, frame threads are important too. The last thing you want is a stuck or snapped bolt. This frame has one set of bottle bosses, the seat lug boss, the gear lever bosses and gear hanger. It has vertical dropouts without any end adjusters.
The seat lug, bottle bosses and gear hanger are all open ended on this frame but you need to be careful with gear lever bosses as they fit directly against the down tube. I have a tap that has been ground flat on the tip specifically for gear lever bosses so it can’t cause any damage to the down tube.
** NOTE Now here is a little known fact. Most gear hanger taps have a M10 x 1.0 thread, but most gear hanger threads are Campagnolo, and they are a slightly different thread , M10 x 26TPI. SB6398 has a Shimano gear hanger which is M10 x 1.0 so my tap is correct, but I’ll be fitting a Campagnolo derailleur which is M10 x 26TPI.
The M10 x 1.0 is actually 25.4TPI and not 26TPI
My point is that you just need to be careful with gear hanger threads.
Seat Tube Reaming
The last task on the frame is to clean the inside of the seat tube. I’m going to be fitting a very expensive seat pin into this frame so I need to make sure it fits perfectly. How many seat pins have you seen with deep ‘zig zag’ grooves in the alloy? I’ve seen lots, so I want to avoid this.
This frame is Imperial (28.6mm) Reynolds 753R and takes a 27.2mm seat pin. You can buy a fixed 27.2mm reamer but they tend to be on the expensive side, so I use an adjustable reamer. They are cheaper but still work ok and give the option of using it on more frames. I have frames with seat pin sizes from 26.6mm up to 27.4mm and this reamer does them all.
I clamp the BB shell in the vice for this task as reaming the tube can be quite tough! A reamer is the same as a facing tool and should be removed from the tube by turning in the cutting direction as you lift it from the tube.
The very last thing to do to the frame is fit the original hardware. Nice new bolts would be lovely, and I would do that on other builds, but this is going to be original, so I’ve cleaned up the seat bolt and bottle boss bolts and fitted them with some anti-seize compound.
So far, I haven’t really mentioned the forks. But the same applies, they need to be cleaned and polished and the bearing faces and threads need to be prepared.
The fork crown race needs to be cut and faced so that it provides a flat seat to the head set bearing, and cut to accept the 26.4mm diameter crown race.
The threads on a Super Record head set are very soft so fork threads need to be very good, crisp and clean.
I run a fork thread die along the threads and check them with a Campagnolo British thread nut (part of the crown race tool). I want that nut to spin onto the thread smoothly, which it does!
The forks are now fully prepped. In fact, the frame and fork prep is complete.
That is a lot of work but it is so important. I started the morning with a frame and fork and ended the morning with a frame and fork, so not much building has happened, but at least when I start, it should be plain sailing.
Now the ‘bolting on’ can begin, starting with head set and bottom bracket – but that is for Part Two!