Building A Uni From Scratch

This is my senior project at my highschool and I’m just getting started. I picked up a “dead” bike frame from Recycled Cycles that is made of Reynolds 531 tubing (Manganese Molybdenum) and just ordered my bearing holders from

Does anyone know what method to use to weld 531 tubing? All types (MIG, TIG, arc, and a few others) and available at school. Anyone know if I can heat and hammer the stuff into shape?

How should I keep the frame at 90 degree angles and perfectly flat while I weld it?

I know there are a few frame builders here and I hope that they can help me out so I don’t have too many tramatic experiences while I buil this :slight_smile:

I hope this helps:


Soo, sounds like ovalized the tubes will be the hardest thing for me to do since my school doesn’t have a press. I’m hoping I can keep the tubes circular at the top then start ovalizing the tubes when they get closer to the bearing holder. I’ll have to do it by hand with a hammer and forge :frowning: I do love hitting red-hot metal but that sounds like a of careful work.

this guy I new made a wood uni

The results aren’t as nice, but you could ovalize the tubes near the bearing holders using a large vice. Only the lower 6 inches of the tubes will have to be ovalized. Place the tubes horizontal in the vice with a piece of steel plate about 10 inches long on each side of the tubing to keep the vice jaws from denting the tubes. You may be able to ovalize the tubes without using any heat by compressing it in the vice, depending on the wall thickness.
If you cannot accomplish this without the use of heat, using a torch to heat the tubing and a vice to compress it will yield much more accurate result than banging on it with a hammer. Leave the frame legs longer than you need them while going through the ovalizing procedure so that you can cut them to length from both the bottom or top to achieve uniformity in the taper. This will make it easier to keep them symetrical

For frame fabrication TIG is really the only way to go. MIG can be used, but TIG will yeild far better results.

Ovalizing the tubing isn’t always neccessary. Using 1/2" round tubing you can make a plenty nice Hunter-esque frame.

Have you considered machining the frame instead? TIG welding is very difficult, and unless you already know how, you probably won’t be up toi welding up your frame by the end of the school year. You will need to make a welding jig, used to hold everything. You then tack everything together, check squareness, and then do the actual final welds.

I am machining a frame from aluminum right now, and it takes a long time to machine, but it works. It’s far easier to learn to do simple milling operations than it is to learn to TIG weld.