Machinability is not a problem and I wold also be using bar stock not existing balls.It might be because I have a fetish for stainless(mmmmmmmmm....shiny). If there is no major problem with using this material I think it will be SS. I know the pricing for off the shelf dent balls is not too bad but by the time I get them shipped to OZ I can't justify the expense. I should be able to knock up a dozen in about an hour so time is not a concern either(arn't CNC's wonderful) I was thinking of using 3/8 unc/whit thread(trumpet sized balls) What size increments would you recomend? I was thinking of 0.0025" steps. If anyone has any photo's of other repair equipment they have made/bought it would be great. So far I have made some bell mandrells to suit my Getzen, conn and ambassadoor. some leadpipe mandrells and I'm making a work jig for holding the trumpets by the bell(similar to the one from Votaw) It's a hobby at the moment.