If you have a metal lathe, then no doubt you've wanted to make a 'Ball Turning Attachment'. One of these fine days I'll make one too. 
One that can be adjusted to do concave and convex cuts.
In the mean time, here is a little trick that works well for concave cuts.
All I did was not to fully tighten the clamping nuts for the topslide clamping plate. I did hand tighten them to limit slop.
I positioned the topslide pivot point 'more-or-less' in the centre of my workpiece ( a nib, in this case) and then locked the carriage. I took a first light 'sweep' over the work to check it was where I wanted it.
By holding / rotating the topslide and just taking light passes, I find that it is quicker, more accurate and leaves a better finish ( less sanding ) than with a file like I would normally use.
The three pics show the sweep of the cut.
One that can be adjusted to do concave and convex cuts.In the mean time, here is a little trick that works well for concave cuts.
All I did was not to fully tighten the clamping nuts for the topslide clamping plate. I did hand tighten them to limit slop.
I positioned the topslide pivot point 'more-or-less' in the centre of my workpiece ( a nib, in this case) and then locked the carriage. I took a first light 'sweep' over the work to check it was where I wanted it.
By holding / rotating the topslide and just taking light passes, I find that it is quicker, more accurate and leaves a better finish ( less sanding ) than with a file like I would normally use.
The three pics show the sweep of the cut.
