would be a lot easier to put the wheel in a manual lathe and open the bore radius .040." should be a simple job.... assuming you can fit the wheel to the lathe.You get the front wheel spigot diameter bored to 60mm. the hub spigot is slightly smaller to account for tolerances. The hole has to be concentric, since the wheels are hub-centric, they rely on the fit to that hub spigot to hold the wheels concentric to the hub. You will need a machinist who can do that part correctly on a CNC mill. Not a hole saw!