Hey,

The .833 is 21.1. I needed a 21.1 stem with a higher rise and longer extension for my vintage Takara touring bike a while back. I found a 22.2 Trek MTB stem that had a 26.0 clamp. I turned down the shaft to 21.1 (using a file and a homemade jig), and have been using it ever since. Funny thing is, I need a shim for the clamp because I'm using a 25.4 straight bar on the bike.

I would think you could do the same. It's not that much metal that needs to be removed, as long as the stem wall is thick enough to begin with. Hope this helps.

2tall