Hi Pilou,
the method you have shown does not seem correct.
Although Lara had drawn his shape straight he then flowed it to get it curved.
The method I showed worked directly on the curved ring so removing the need to flow.
Your cutter as a straight cut through it not curved to match ring.
Also there is no chamfer.
Hope this clarifies the method.
Barry

I made a chamfer and then Fillets on each side of the chamfer...
...but surely miss something...because the video is some speed ...(maybe my fillets are too strong)
if you can make a little image for clarifyed... (or a 3DM of the cube...

Hi Pilou,
hope the attached photo's help.
Cheers
Barry

Perfect i had just added one fillet more on a side on my cube so false result! :)

Seems more easy than the analytic Michael's method!