Creating a Sphere on the end of a shaft

[Rick_B]

I would like to put a sphere/radius on the end of a 1/2" diameter shaft using a 12" lathe. I know there are a few different ways to do this but I am specifically interested in a method I have heard about that involves turning the sphere using the swivel function of the compound rest. Has anybody ever heard of that? If so, can you point me to something that goes through the set up?

Thanks
Rick

 

[woodchucker]

I have done this. it's a piece of cake if you have a SB 9 or 10. I don't know about others.
Basically you simply put a turning tool or preferably a HSS threading tool into a holder, and set the carriage under the end to be turned... on the radius center. then you back out your compound and enter slowly while rotating the compound in the arc. Each arc you advance the compound until you reach the desired size.

 

[RJSakowski]

I have used that approach to cut spherical mirrors on an Atlas/Craftsman 6 x 18" lathe. I loosened up the set screw to provide a slight amount of resistance. I was cutting mirrors with a 7.5" radius. To cut a sphere you will need to have the cutting tool behind the pivot point which may require some inventive tool fixturing.

 

[markba633csi]

You may need to add a handle of some kind to increase your leverage and control of the compound as you swing it around
As RJ mentioned you want to adjust it so that most of the compound slop is taken up plus a little resistance

 

[Rick_B]

I have done this. it's a piece of cake if you have a SB 9 or 10. I don't know about others.
Basically you simply put a turning tool or preferably a HSS threading tool into a holder, and set the carriage under the end to be turned... on the radius center. then you back out your compound and enter slowly while rotating the compound in the arc. Each arc you advance the compound until you reach the desired size.

OK - I m glad to hear I'm not crazy for thinking this was a method. However, I'm not visualizing the set up - would you happen to have some pictures or a link to a youtube about the set up? FYI - I am using a clausing 12" lathe with an Aloris tool post if that matters. Thabks fir your help

Rick

 

[RJSakowski]

You may need to add a handle of some kind to increase your leverage and control of the compound as you swing it around
As RJ mentioned you want to adjust it so that most of the compound slop is taken up plus a little resistance

I was using an Armstrong tool post and just used a pair of vise grips on the tool holder. If the tool is long enough, you can grab the back end of the tool.

 

[BGHansen]

I've use a corner-radius end mill. Mount the end mill in a QCTH. You'd need a 1/4" radius end mill for your 1/2" shaft. Another option is a pre-made radius lathe tool.

Bruce

 

[Rick_B]

Thanks Bruce - I may end going with a pre-ground tool. For what they cost you can almost buy one of the cheap ball turners on amazon - do you have any experience with them. I've read some reviews that indicate they are not good with steel? Also - I would really like to get my head wrapped around the swiveling compound technique.

Rick

 

[woodchucker]

Thanks Bruce - I may end going with a pre-ground tool. For what they cost you can almost buy one of the cheap ball turners on amazon - do you have any experience with them. I've read some reviews that indicate they are not good with steel? Also - I would really like to get my head wrapped around the swiveling compound technique.

Rick

For the life of me, I cannot figure out how I got the swivel to work. I went down to shoot a video for you and can't reproduce my results.
I know I turned the first few balls that way, and was proud of the fact that I did it without a tool.

I just gave up. And will think about it again.

 

[Rick_B]

For the life of me, I cannot figure out how I got the swivel to work. I went down to shoot a video for you and can't reproduce my results.
I know I turned the first few balls that way, and was proud of the fact that I did it without a tool.

I just gave up. And will think about it again.

I don't understand - that has never happened to me I keep looking at the compound and still can't figure out how to get it to swing a convex arc
Rick