Or at least the way I went about sorting the inaccuracies in my mandrel that were driving me mad.
I decided the best option was to fit a 1/4" shaft to my mandrel, this would mean I couldn't use it for slimlines etc as those brass tubes wouldn't fit but more on that latter.
I started by enlarging the hole in my mandrel with a hand held tapered ream
This gave the sort of fit on the shaft that I'd hoped for as previously I'd had to shim the old shaft, you can see the mandrel on the back of the vice in the next photo.
I then turned my attention to the bushings & once again reamed these out.
I also found I needed to ream out my mandrel saver but as with the mandrel & the bushings the amount of material I had to remove was minimal but the fit I now have is as spot on as I think I could get, it just means any new bushings I get I will had to ream out to suit the 1/4 shaft.
As for slimlines etc I've managed to concoct a couple of mandrels out of bits & pieces I've come across as I've been sorting my pen turning stuff out. the shorter shaft of the middle one in the photo will only allow one half of a pen to be turned at a time but fits the tubes better than the longer one (bottom mandrel)which ironically is the new shaft I bought 
