There is another way to cut spheres (or concave or convex shapes) on the lathe.  Actually, you can cut any kind of curve you can think of.  Essentially what you do is calculate the necessary x and y positions that the carriage and crossfeed needs to be at in order to create a series of steps.

For a sphere I start making the right hemisphere by putting the left edge of the parting tool at the middle of the sphere, and then continue to the right adjusting the carriage and crossfeed according to the results of the trig calculations.  For the left hemisphere, I put the right edge of the parting tool back at the middle of the sphere and start cutting to the left.

When you're done with this process, you have a series of steps with the inside corner of each step lying on the sphere surface that you're trying to create.  You start filing these steps down, and when the steps are all gone, you have the desired sphere size.

Metalshapers: turning a radius on a lathe

I originally found this idea in a Guy Lautard book, but I ended up running my own calculations because I found myself getting annoyed at the seemingly illogical way he had done his calculations.

It sounds like it would take awhile, but I found that the doing the calculations took longer than actually making the cuts. A dedicated sphere/concave turner might be faster, but this method allows to you cut any profile once you've calculated the x and y postions.

i ended up getting one =D

harborfreight8x12 said:

jeremy0203 said:

i ended up getting one =D

Hi Jeremy.  What type did you get?

Regards, Al

steve bedair design. although it may be up for sale in the next month or two because im 90% sure ill be converting to cnc on the lathe very soon.