I need to make a more precision 5/16" mandrel for a diamond drum to put in a mill. The rubber-tire types used for sanding drums SUCK really badly for runout, and it's not just the rubber- the steel mandrel inside it may have 30 thou of runout or more.
I used a 5/16" bolt on the Sherline, it had much lower runout at firsy, but in the final cutoff stage the parting tool bound up near the end and it bent it. I found that on the whole it just bends too easily.
I could get a higher grade bolt... or maybe a screwdriver shaft?? Just looking for stiffer steel here.
Also I may need to make a similar custom mandrel for a Dremel bit. Well the screwdriver shaft, I'm probably not gonna find a 5/16" shaft for the first type of mandrel I just described, but I could probably use it for this Dremel one.