Sphere Jig

[Peter Blair]

Don, this is really nice looking and I'm certain it would work great but I am not certain that I could make the unit as well as you did, and I really don't have a means to power it as you do. Thanks for the ideas.

[Thom Sturgill]

Peter, I only recommended that you look at FluteMaster to see his mounting for the grinder/foredom handle . For a sphere you must rotate around the centerpoint which I'm sure your rig does. Morris had to go through a critical setup each time he uses his rig. That could be improved by having guides on the bottom of the mounting plate that guarantees alignment to the bed.

I'm not sure that there would be any advantage to rotating vertically, horizontally or diagonally. Conventional wisdom is that a scraper should cut on or slightly above the center line with a slight downward slope at the tip. This would tend to lend itself to a horizontal motion IMHO.

On the other hand getting the center point right only requires a one time set up for the banjo mounted vertical solution. It would seem that that would cut from the end to the vertical equator stepping inward as you remove material and then you would have to remount and that would be problematic. You would need a cup to hold the sphere and some way to hold pressure but that might get in the way of the rig. I would have to see one in operation to see how they handle that.

[Peter Blair]

Understood Thom.
Thanks for the suggestions.
In action the cutter is simply set up on the center of the lathe and then lowered after each cut to finish the sphere. It appears in the video to cut rather than scrape . .
Yesterday I messed around in my shop and made a few modifications to my jig. I now am utilizing a small Hunter "cup" style carbide cutter which cuts much cleaner bit with it on center it tends to be a little grabby if too much of the cutter is involved in the cut. This is not a big deal, just means that I need to make sure I cut fairly close at the headstock end before using my jig. It cuts clean enough that I think I will only need to start sanding at 220 rather than the 120 that I have been starting with.
This cutter comes with a 1/4" square shank that is raked and tilted a little but because my jig uses both sides of the cutter I had to set it up with the cutter top parallel to the ways.
I will continue to see if I can devise a router based jig but from what I have on hand the cutter is too close to the mass of the router to get very close on the Headstock end.

Thanks again for all your suggestions.