Making a mandrel

[MechanoMan]

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.

[jalessi]

What about a 5/16 expanding internal collet?

http://www.jfkprecisionproducts.com/internalcollets.htm

[blades]

Do you have a tool supply place nearby? They would have steel dowel pins or drill blanks you could use. Or if that's too hard of a material, I think you can get steel round stock from Lowes or Home Depot, which would run more true than a bolt.