Hi.

I have an old Japanese folding bike, threaded fork, 22.2mm insert.

I want to make use of my alt bar, but the stock quill stem is a single pinch bolt type so, I can't slide it in.

I'm thinking of making a quill stem and clamp a stem with removable plate.

My idea is using a 22.2mm steel seat post and cut an angle below to match the wedge.

The question is, is it safe?



Handlebar and the quick release mechanism.

safe? Probably not 😳

hmmm... 22.2mm... a schwinn seat post?
gotta be stronger than one of these i guess.... they're aluminum...
Ebaty Search: "Adapter 1" Threaded Fork to 1 1/8" Ahead Stem 22.2mm 150mm Alloy"

the quality of the welding you mention, and any ANNEALING required to reduce embrittlement, is what will matter the most.

Velo Orange and Nitto both make quill stems with removable faceplates. You can also use a threadless stem with quill adapter.

I've built a few quill stems. After cutting the angle of the quill I'd braze a short length of tubing inside and cut it again, so the wedge had a good surface to push against. I don't recall the details, I guess we were using 7/8" 16 ga. seamless for the quill and 3/4" for the insert. Then a 1" collar at the top to give lots of area for attaching the extension, which was probably an offcut of 531 seat tube notched and squashed to fit the quill, and similarly at the clamp end. These were not lightweight but they were strong, they were for specific use cases like my girlfriend who needed a very short stem, my experiments with funny handlebars (a few tandem stoker stems too, but they weren't quills obviously).

You can find face plate quill stems on Ebay and whatnot for <$20 all day long:

What diameter is your 'alt bar' now?

"is it safe?" Depends on how well one can fabricate. I always get a bit of a smile when I read this type of question. The folder's stem was made by someone's hands and it's proven to be safe. many of us here have made their own (and their stoker's) stems and not have had failures. So to paraphrase an old slogan "only you can prevent unsafety".

There have been a few stem kits that builder suppliers sold BT (before threadless). Basically what grumpus described but without the added wall at the wedge cut or at the quill's top either. The handful of self made stems I've done didn't have any issues with a single walled quill but I did choose fairly thick walls (.058" IIRC for the quill). here's a shot of our tandem that has both stems made by me (as well as a custom brake cable hanger and some of the rerouted cable stops). The bar clamp uses M5 bolts in binder barrels patterned after the common M6, but down sized by about 80% (and I still have some of these binder barrels available). The two bolts have held the bars quite well.

If you do try to make your own stem (or mod an existing one) take care with the alignment. With bars that have a 20"+ width any slight misalignment will be greatly magnified at the grips. Tacking and checking will be your friend. Andy

I should think a seat post would be strong enough, unless it’s off some lightweight kids bike.