Hi Gwaai, I’m not really familiar with your type of dentisis drills
but I can tell you that on Brush-type electric motors it is fairly
common to see sparks at the brushes. The smell is most often
associated with ozone that is produced by the electric sparks in an
oxygen atmosphere like air. The tool that shows larger sparks may be
in need of new brushes. If the brushes are worn down it can make the
motor tend to overheat and this too can cause an odor. Please
remember to keep safety in mind with these tools. Those sparks are
quite able to ignite flammable fumes from solvents or gasses from
torches. Make sure there are no concentrations of these in your work
area by ensuring proper ventilation.
You may need to contact the manufacturer to get new brushes for
these tools. I advise folks to always have an extra set of brushes
on hand. Breakdowns in the middle of a project can really disrupt
the creative flow. I hope this helps you out somewhat. There are
lots of knowledgable people here at Orchid that probably know more
about this than I do.
Mike