i built a jig stand for a dremel with carbide wheel but that just became another dedicated machine in a shop with too many of them already.
so now i just mark the length on the shaft (any shaft material) with a sharp pencil and then free hand cut off the excess with a carbide dremel, making sure to leave 1/8" proud of the mark. i square up on a 6" bench sander loaded with 120 grit gold 3m. for carbons, i always slow-set epoxy in the insert and make sure the epoxy smears 1/4" above the cut line, to "soak" the cut end well.