Thread: This weeks creation.

My lathe is two or three sizes up from yours at 280mm swing and 700 BCs so you would have to scale it down to fit your machine. Size isn’t really an issue as there isn’t much pressure on the cutter when in use. That said, My pivot axis is 16mm and the cutter head post is 14mm, I wouldn’t go much lower that 12mm for both posts.

The base needs to be a little longer than the tool post to allow for the handle/wheel on one side and the cutting head on the other. The section on the base that is clamped in the tool post shoulkd be milled down far enough to allow the pivot axis to be a little lower than centre height. If you only want round balls, then set the pivot axis at centre height.

Mine will cut a 60mm ball, but that’s a bit over the top I think, probably a 25-30mm ball would be ample. The bigger the ball size it will cut means the cutter post will have to be longer, the longer the cutter post is the further the work will need to be from the chuck to clear the bottom of the cutter post

A simple L shape cutter head is fine but I suppose if you have the machinery you could shape it in an arc thus giving more chuck clearance.

My cutter post mount is a simple 14mm hole through the pivot axis with a lock screw engaging the post from the side. A better idea iwould be to make a clamp style cutter post mount similar to a bicycle handlebar clamp. Easy to make, just drill a hole through the pivot axis for the cutter post , cut through the middle of the hole at 90 degrees to the pivot axis with a slit saw then drill/tap a 4/5mm hole either side for clamping screws. Probably better off drilling the holes before using the slit saw though. Either usea low profile heads for the clamp screws or countersink them so they don’t interfere with the ball.

Hope that makes sense!

A couple of drawings:
First drawing shows pivot axis with cutter stem mount on left (showing a better cutter head post clamp), on the right is a plan of the base showing hole through which pivot axis slides and at bottom is the handle.

Drawing on right shows cutter head and post. Top of post should be turned down a few mm smaller for cutter head to slip over. Top of post should be drilled and tapped and a screw and washer hold the head in place.,:

Thanks for the drawing. Now to find the time to make it.
Kryn