On Mon, 23 Apr 2018 22:10:53 +0100, "Andrew Mawson"
wrote:

snip

Did you design this tool yourself Andrew? A thin walled tube with a
couple of lugs up inside a bit to give you some turning purchase?



I drew it up in Fusion 360 and printed it on my Cetus 3D printer - it's a
simple tube with two ridges on the inside. The dimples are only 2mm wide so
difficult to do with wood and screws, but dead easy with a 3D printer

Do you use a .stl output file and would you be willing to share it OOI
Andrew?

I
suppose without the 3D printer I could have milled one out, but not an easy
operation.

Quite. It's not one of those things you would buy (or build g) a 3D
printer for but once you have one it sounds like a good use. ;-)

Cheers, T i m