Or presumably plastic knobs also. Owner of Roland piano had a flight case
made up for it but he did not allow for the knobs. Hacking into the foam
still leaves the knobs pressed against the outside face of the case.
Replacement knobs not possible as would have to be only 8mm high and do not
exist that shallow.

How to mount in a lathe to cut down ? Cutting tool sufficiently sharp but
grip the knob in the jaws too tight and the Al of the knob deforms. Too
loose and it slips of course. Jubilee / hose clip around it and not enough
space between the jaws for the clip boss.
Nylon cable tie worked well enough to form a neat level line to then hand
hack saw / and bench-grind down to, but not enough force to fully lathe cut
the height down. Anyone been here before/ know the secret? for the next time
I'm confronted with the same predicament.
Perhaps an engineering solution, if an oft repeated job. A 5 to 10 mm thick
anulus of aluminium , with a radial cut and dimensions so a tight and
rigidly held grip in the lathe-juck.
Perhaps a smaller ground down boss structure of a jubille clip , for a more
general work-around, replacing the tightener with an Allen key grub screw
(hex set screw) to reduce the size.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/