Boring out the spindle nose adaptor

Lots of distractions since the last post due to business trips (Korea, N Ireland etc), family, birthdays, dog, bathroom update etc etc. Finally got some workshop time last weekend and made a start on rectifying the cockup on the spindle nose adaptor. I needed to deepen the tapered bore by around 1.5mm to avoid the adaptor bottoming out on the spindle nose taper which seems to be longer than the ISO spec suggests it should be. 

I'm suspected that the Tree spindle nose dates from a period when the ISO spec was either in its infancy or hadn't been defined, given that the Tree was made in the early 1980s and the ISO spec was published in 2009. These tapers were US inventions, from what I can tell. Certainly, the Tree spindle nose includes imperial threads which again are not shown in the ISO version - but perhaps that shouldn't be a surprise.

Anyway, here's the 4-jaw chuck removed from the spindle and the adaptor fitted. 

FWIW, here's the state of play of the adaptor:

Let's set it up and see what we are dealing with:

At this point, The Stupid Fat Bloke slapped some Plastigauge worms in between the adaptor and the spindle nose. These are made of a fairly viscous wax. He managed to squash them down to around 50um thickness. But so what? Assuming we actually had zero mechanical clearance between the parts, he'd never be able to fully mate them with a slug of thick wax between them would he?

After seeing this nonsense, I thought it best to take over and do the job properly. Namely by fitting the adaptor, checking for zero clearance at the joint and then checking the runout.

That's something like 200um max axial runout on the front face

..an about 30um radial runout on the taper. I will start by skimming the front face. Then I will see how tight the taper actually is - ie how much if any I can remove from it.

But first, I need to extend the bore at the back of the adaptor. Like this, which is just over 1.5mm...

..using one of my Chinesium carbide boring bars.

That fits rather nicely, so now to finish machine the front face of the adaptor once it's fully mounted in position.