In article ,
Ignoramus6679 wrote:

Thanks to Steve's, he lent me a MT5 test bar. It fits into MT5 opening
in the spindle. My problem is that there is some sort of crud (or
rust) in it and the bar does not seem to be well aligned. So I would
like to remove that crud by some non-intrusive means, any ideas how I can do
it without runing the accuracy potential of the spindle.

What I use for crusted oil spooge is mechanical scraping (to get the
bulk off) followed by acetone (which gets the last residue off).
Acetone will also strip paint, so be careful where it splashes or runs.

Then shine a very bright light into the bore and take a look.

I ended up very lightly stoning the inside of the taper to take the
dings and rust spots down, the point being to grind away only the stuff
that sticks up above the surface.

I also used the hi-light blue and selective sanding approach to find and
remove some larger dings.

But do all this with great caution, to not make things worse. The
surfaces need not be pretty to mate properly and yield low runout.

Joe Gwinn