Hi Ian

If it was me, as you have a lathe, I would get a 1/2" or 14mm length
of cold rolled steel, chuck it up in the lathe and drill a fitting
size hole in there, drill another small hole to cut thread into for a
grub/setscrew, that's all you need, then a small flat spot on the
forstner bit shaft and you have what you want, (at low cost).

http://homepage.mac.com/l.vanderloo/PhotoAlbum4.html

Have fun and take care
Leo Van Der Loo


On Feb 7, 10:10 am, "Ian Malcolm" wrote:
I'm aiming to make some tall hollow forms and want to start the hollowing
with a forstner bit. Anyone know where - in the UK- I can get extensions for
forstner bits (which have 5/16" or 8mm shafts)? The extension bars for flat
bits don't fit.

TIA

Ian