Posted by not done it yet on 04/11/2017 06:42:51:
5C collets also fit spin-indexers , indexing fixtures, and other gadgets. To the best of my knowledge none of these things are made for ER.
Knowledge improvement time!
I believe you will find, if you look hard enough, an ER spin indexer available from ArcEuro. Named after the late John Stevenson?
It will accept both 5C and ER32 collets. Look it up, along with the square and hex indexers.
They cheated. It is a 5C indexer with a 5C/ER adapter. Actually, the 5c/ER adapter seems like it would be a great addition to my shop.