Robert Swinney wrote:

General question: Can't the 5-C collet holding "spin indexer" be used for
sharpening the flutes of end mills?

Yes, occasionally. Do much more than that and the grinding swarf will find its
way into the unshielded mechanism, and you will be buying a new indexer. A good
friend of mine, excellent machinist, had this happen to him so I know this is
true. Maybe it might be possible to modify an indexer with a plastic seal ring
or something to help keep grinding grit out, dunno.

GWE