So this is something i have been pondering about for quite some time. Not only is there a problem setting this up in my machine due to its size, but ridigity soon comes into play as well where my boring head is of the flimsy crappy kind and i need to hold it in my ER32 collet.. So it stacks up quite fast. (W20 boring head is wanted, anyone? help?)..
Any way the basic principle for this is using the mill as a lathe setting up with some trigonometri and move the piece of metal your cutting by hand instead of letting it be stationary.
This would be the basic principle crudely showed. A cutting plane in the form of a circle gets created and the it will cut the the spherical shape by ofsetting it in 45deg. Note now, 45 deg is what you will need for half a sphere. Lets say you wanna cut a dish or parabole then you need to rethink your trig. The base triangle will shift with the new approach to the material.
I set this up so i cut from center and out instead of the usual way from the edge to the center.. This is cuz i have issues with clearance. And my rotation table is large as – !#%%. Anyway last image in gallery is the result of the testing. Cut from a 30mm piece of aluminium roundstock.
So what could this be used for? Well, seen balljoints?? Those nifty little things that you can bolt through and they have full range of motion.. Well the dish shape cut into the plastic bearing of those is a part of a dish. So calculate how much contact the bearing will need to have with the ball and you can make your own joints. Or why not molds? Or the end of a pressure container thats get screwed and welded into the end of a pipe.. The applications is quite a few actually.