[CV3]

I generally use 5/16th threaded rod when attaching a topper or cane handle to a shank. And I used a 5/16th drill bit for the hole. A woodcarver friend who makes a cane now and then but is more into caricature carving shared a tip with me. If you drill the hole with a 19/64th drill bit the 5/16th threaded rod will screw into the wood threading as it goes. This has two advantages, first is you can dry fit with real accuracy and second you can glue without clamping because it just screws down tight. I do not know if these sizes are available to our metric users but I am sure there are sizes that will work the same 5/16th = 7.937500MM rod. Drill bit 19/64th = 7.540625 MM . Because the fit is very tight little epoxy is needed along the threaded rod. Too much and there can be an issue in a tight fit. This can be corrected by scoring along the side threaded rod with a hacksaw to give an escape for the air and glue.
I was able to screw on the collar and shank on this cane. I should note that Have a number to toppers with the 5/16th rod already in them when those are gone. I will most likely just use the 19/64th bit for both.handles and shank.

 

[Gloops]

Coming along nicely and thanks for the tip its worth a try, should have the imperial sizes in my old drill stock, deffinitely an advantage for dry fitting.