What I'd recommend is to find a metric to inch conversion chart. Knot size varies so you will have to adjust your your bit size accordingly. Expect a learning curve to figure things out, plug size and true knot size can and will vary. I like using forstner bits. To answer your original question the hole in the handle above is 1 3/64". I had to use a dremmel to slightly enlarge it.
Just ordered some bottle stopper blanks from PSI, maybe that will get me off my backside to get the lathe.
This brush turning might just be a sideline for him. His true calling seems to be in the excavation business, he's very passionate about it.
With all the utilities going underground these days, every town/city needs at least one good excavator. Keep diggin' Sparky!
