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Nice, Jo! Could you give us a shot of the "up and over" ball-turning tool?Simon
I find it easier to just hot up a couple of the correct sized ball bearings to soften them, then drill and tap to the size I want.
This is my spherical turning tool I used for this job:I built it using the Hemming way drawings. It is fairly simple just a tapered boss running in a head that is on a rotating mount. The only important measurement is that the tool holder holds the piece of tool steel at 7 degrees. Looking at the drawings I also need to make the internal tool holder. Jo
Other means of making spheres include form tools, which I use for making the smaller ones the 8mm was the limit to what I would look to use this tool for. Softening ball bearings to use can be hit and miss, I find I have to try to soften 4 to hope to get two that my drills can touch.You can also get spherical turners that mount on the cross slide and go around the work rather than over. To use these you have to take the top slide off. But where the up and over tool only needs about an 1 1/2" clearance to the chuck, these need a lot more.Jo