I, too, wondered why all the fuss about making a ball turner and tried the approach mentioned above of making a simple insert holder that mounted in place of the tool post to take advantage of the compound's ability to rotate.
It didn't work out well. The compound on my rockwell 11x37 doesn't rotate freely enough even though the surfaces look like they should. Since it doesn't have to, I imagine the mfr. spent no time trying to make it do so.
Then I looked at one of the Lautard books to see what ideas he might have and hit paydirt. His method is to calculate the coordinates of a selection of points on the circumference of the desired circle and sculpt it with a cutoff blade. His conclusion was 'why would anybody want to spend a week making a ball-turning attachment'.
It was pretty easy to write a computer program to calculate and print the coordinates so then I just hung them over the lathe, stuck a magnetic dial indicator to the ways and turned the dial while moving the carriage. worked slick, and better yet, when I decided I'd like to make segments of ellipses instead of just circles it was straightforward to change the program to do so.
Marv Klotz has a program that does circles plus IIRC a curve-fitting one.
I've since fitted a chinese digital scale to the lathe which eases the process further.
someone handy w/Excel could do the same thing, but my experience w/printing spreadsheets has been pretty discouraging.
It didn't work out well. The compound on my rockwell 11x37 doesn't rotate freely enough even though the surfaces look like they should. Since it doesn't have to, I imagine the mfr. spent no time trying to make it do so.
Then I looked at one of the Lautard books to see what ideas he might have and hit paydirt. His method is to calculate the coordinates of a selection of points on the circumference of the desired circle and sculpt it with a cutoff blade. His conclusion was 'why would anybody want to spend a week making a ball-turning attachment'.
It was pretty easy to write a computer program to calculate and print the coordinates so then I just hung them over the lathe, stuck a magnetic dial indicator to the ways and turned the dial while moving the carriage. worked slick, and better yet, when I decided I'd like to make segments of ellipses instead of just circles it was straightforward to change the program to do so.
Marv Klotz has a program that does circles plus IIRC a curve-fitting one.
I've since fitted a chinese digital scale to the lathe which eases the process further.
someone handy w/Excel could do the same thing, but my experience w/printing spreadsheets has been pretty discouraging.