So, this ball cutting and hemisphere cutting buisness has got me taken and i was in the mood for a "what if" - and this is what if your to damn lazy to make a radii cutter for your lathe.. But you have a mill, boring head and a roundtable.. This is not thaaat uncommon most of us has lying around actually..
So the goal here is to produce a hemispheric space in a piece of material, it could be a parabolic shape or just for the sake of it a radii of a diameter. To some on the board this is water under the bridge.. for me that hasnt worked in a workshop better part of my life and im a bit mathematically challenged i hade to figure this out with a visual aid before i figured out.. its only trig.. isnt everything we do bloody trig. ;)
So what you see here is a 60mm diameter hole, to cut that with equal radii all around, depth and width, you would need to pick out your calculator and see, what is the cutting diameter for a 30x30xY triangle in 90deg. well as it seems thats 42.43mm. you cant for obvious reasont not cut that deptin in one go.. But you step lathed/turnd forehand you would more skim out the "extra" material.. So by setting your workpiece in 45 degree or in my case just tilt the vertical head, you would feed the workpiece rouund and round on a turning table, and for every 40 turn or so (depending on your round table) you would feed the setup down that much your confident your machine can take out.
So i hope this visual aid, helps you guys out as much as it did me.. =)
This will work with a flycutter, boringhead and well such things..
Not sure if this was a howto, so i posted it in How Do I, someone can move it, if its in the wrong section.
