tubing answers for threadless stems

Hi Vincent

None of our esteemed mentors have replied for four days; so here are a few thoughts from me.

As a first step into the world of framebuilding I would like to start by welding chromoly threadless stems, in different clamp diameters. I made some research and think I have kinda figured out the tubing selection, but I would need some reassurance.

1. What is generally the O.D of the extension tube? From what I have gathered it seems 1-1/8" is the way to go, independently from handlebar clamp diameter.

yes, this is a good place to start.


2. The most suitable tube I found for a 25.4 handlebar clamp tube was 1-1/8" (28.6mm) O.D, 1.009" (2.62mm) I.D and 0.58" (1.47mm) thickness. My question is, what dimensional tolerance do I have for the handlebar clamp diameter? Could that extra .22mm cause problem? Other option I found was 0.995" (25.27mm) I.D with .065" (1.65mm) thickness.

that .22mm will cause problems. the 1.65mm wall, and a reamer, is a better solution.

3. Is .058"-.065" (1.5mm-1.6mm) thick enough for stems? Would .049" (1.25mm) be suitable for the handlebar clamp tube only? I would like to make 26.0 clamp stems too, but the only option I found is 1-1/8" (28.6mm) O.D, 1.0270" (26.08mm) I.D and 0.49" (1.25mm) thickness.

i personally would start and stay with thick stuff. if once you're super confident and competent there, you want to begin exploring, thats up to you. Again, a reamer and/or small lathe is your friend here


4. Where would one order tubes and binders? I did manage to find tubes on Aircraft Spruce and other websites, and M6x1.0 binders on Nova Cycles Bike Fab Supply (althought I'm not sure they would work for every handlebar clamp diameter?), but I'm still curious if you have other resources.


google is your friend here, paragon machine works, bikefabsupply , framebuildersupply.com


Thank you for the help

also, we use first and last names attached to each post here, its a rule.

post up some photos of how you get on!

I will agree to a large degree with what Patrick says.

The few stems I have made have used 1"x.035"tubing for the extension. In my eyes bigger is more an aesthetic issue then a functional one.

I suggest using a reamer to size the bar clamp after brazing/welding the stem as distortion will be a real happening. Here is where thicker walled tubing is better for a beginner.

Straight gauge 4130 tubing is available from a number of industrial suppliers like MSC or Master-Carr. Other non bike world sources are Stockcar Steel and Aluminum. I have ordered various tube s in 3' lengths for future projects from these suppliers.

While the common M6 binder barrels, as used for seat post clamping, will work well for the stem I find a slimmer/smaller M5 binder looks better and holds well. I have had my own stash of these made up by a job shop. This is another reason that a lathe is a beautiful thing, turning out a couple of one offs is easy. Andy

Or just use the stem kits Dazza has developed for stems https://www.framebuilding.com/Llewellynstemlugs.htm

Thanks everyone for your insights, making stem definitely requires more equipement than I originally thought, guess I will have to wait and invest in a small lathe!