I don't think you'll find many .833 stems with the looong (tall) quill that the Technomic has, but that would be preferable to modifying your stem. I have turned a stem in a lathe and reduced the diameter, but the shape of the piece makes it a difficult job: the angled portion threatens to smack your hands or interfere with the cutting tool, and you have to hand-finish the end of the quill that you had clamped in the chuck. But it insures that you get a more accurate, and more even, diameter...not a job for most people who don't have a lathe to take on, I think, and sanding off that much material would get *really* tiring.