HPosted by Vic on 15/11/2021 21:44:42:
Thanks John, all useful info. At some point I need to grind a tiny boring tool for jobs like this!
Best way is use say 3/16” dia HSS and grind similar to the ones at the RH of this photo, more pics In my albums. You need to reduce the cutting end only to about half the diameter, grind some clearance behind this, simple to do free hand. The only reason for boring the collet after drilling was to ensure the hole was straight before reaming.

Edited By JohnF on 16/11/2021 09:49:48