Going 'round and 'round

[Brett Baldwin]

This is a project I whipped together real quick for my dad who is visiting. He is doing a Tai Chi Ball class and wanted a real wood ball for it. I had to do some quick research and some mickey mouse engineering to get this to where it is now. I tried freehand at first but my diameter kept shrinking and I needed to keep it fairly big so I created a radius jig based on some designs I found around the net. It held together long enough to get something reasonably close to a sphere. The wood is Bass because I knew it would cut easily and I didn't want to waste good wood on the prototype. I gave it a quick coat of BLO heavily cut with mineral spirits but it won't be getting any more finish because it will need to be gripped for the class. It is 6.25" in diameter and weighs in at 2.6 pounds.

By itself:
70450
With my shades for a reference:
70451

If anyone has some ideas or suggestions for building a good radius jig I'd be interested in hearing them. He would like an 8" one in walnut eventually.

[Doug M Jones]

Neat idea. You must have mastered the skew or son of skew. I have a hard time getting a smooth radius on a spindle and you can do one big radius.

Well done, I'm sure your father will like it.

[joe greiner]

The late Jean Michel made the ball jig shown here:

http://www.atbq.qc.ca/jm2/boules.htm

This is for a specific size. It would probably be simpler to make a separate tool holder for each size, than to devise an adjustable radius.

Home page derived from his work:

http://www.atbq.qc.ca/introjm.htm

Joe

[Mike Vickery]

Looks like your prototype is a sucess to me. Nice job.

[Brett Baldwin]

Thanks Joe, that was actually the one I based my jig on with a healthy dose of artistic license. My armature wasn't beefy enough and needed a bigger base to support it. All in all, it work well enough. If I do another this size, I'll be putting in more head scratching time.

[Fred Morton]

Hi Brett,

I have been a long time lurker on this forum. I thought I would take the opportunity to introduce myself as I have traveled this road in regard to making a sphere.

I don't pretend to have invented the idea but I have built a ball cutter (also with a healthy dose of artist license). Having been an amateur woodturner for the past nine years (with a full time job) I realise that turning a freehand and accurate sphere without the constant practice of a professional is very difficult. So making a ball cutter was a good option for me. Being an ex-mechanic with some metal skills has helped in building this ball cutter (see pics). It works very well.

I have really enjoyed visiting this forum.


Fred

[Brett Baldwin]

Welcome to the posting side Fred. That's a great looking jig. I really like the shear scrape aspect. Mine was a similar thing with a bowl gouge as the cutter.

If you don't mind my picking your brain a little, do you find your armature flexing much? I found mine was lacking support when it went off the base and flexed down (of course it was 3/4" plywood). Also, what are you pivoting on? I used a nylon sleeve with just enough extra to not bind the armature but I was thinking a bearing would be better for a more permanent jig.

[Fred Morton]

Hi Brett,

Thanks for the welcome.

So far I haven't had any flexing problems. I have a small metal lathe, so I turned a spigot and a sleeve (pics will explain it all) to allow the tool to pivot. This was the best option for me but a bearing would be good.


Fred

[Mike A. Smith]

Brett, please bear in mind I haven't tried this myself, but if you aren't going to making a lot of these I have heard folks say that if you use a 'cup' chuck you can rotate your turning axis multiple times to get the sphere shape. I'm sure that's clear as mud, but maybe some of the more experienced guys can explain it better.

[Brett Baldwin]

In fact I know exactly what you mean Mike and I used one to do the sanding on this. The problem with freehand at this point in my skills is that my 8" diameter ball would be lucky to be 5" at the end. I have a problem with that much waste of both material and time. We'll see how he likes this one and I'll be brainstorming the design until then.

Fred, that's a nice simple rig with what looks to be an ample amount of adjustment built in. Now that I see the pivot, I see why the flexing isn't an issue for you. That will definitely be an inspiration for my next one.