Radius turning tool vid

[kustomkb]

Here is radius turning tool I came across on U-tube. I thought it was a pretty great idea. It looks like he is adjusting the radius by moving the pivot points in T-slots. I suppose a guy could drill indexed holes for preset sizes.

[ame]http://www.youtube.com/watch?v=biwGh8GsJtc&feature=mfu_in_order&list=UL[/ame]

[ame]http://www.youtube.com/watch?v=u2cqmSFYRDE&feature=related[/ame]

 

[kd7fhg]

Looks like it works on the same principle of a rotary table.

 

[Bill Gruby]

Looks to me like its cam drivin.

"Boll Gruby"

 

[BillTodd]

Clever idea

It sort of works like this: (which was an idea how to cut a semi-torus in a lathe.)

 

[marcel]

looks like this

 

[Paulsv]

It seems to me that the ball this tool cuts will be out of round by the thickness of the cutting tool, since it is cutting with both sides of the tool. Wouldn't the ball diameter be smaller in the x axis than the y axis by the width of the tool? Or am I thinking about this all wrong?