Originally Posted by JerryFlyGuy  ...... One thing I wonder about when it comes to extensions is.. how do you insert the tool into the extension and keep it all concentric with the shank of the extension?..... |
One way to get the extension as concentric as possible is to finish bore the hole for the cutter with the extension mounted in its holder on the machine. Just grip a little boring tool in a vise.
This is not practical for you I would guess and I think you would simpy have to live with things not being nicely concentric...........but as I typed this a wild idea popped up into my head; even before my morning coffee!
An Outrigger Bearing carrying its own collet holder. I did this once on a small mill. It is possible to get ER25 holders on precision ground 1" dia shanks. Fabricate a bracket that can attach to your spindle housing and have a pair of bearings at the end. You don't need really fancy bearings because you are not worried about long life and any bearing will be more accurate and stable than a long whippy extension.