"Ring scrapers"

[János]

Hello,

I need your knowledge and help! I have read a few articles about turning spherical objects on the web. One of them mentioned a "ring scraper" for smoothing spheres. I know the basic geometry laying behind this, but never seen or used such a tool, and my books do not mention it. I use standard gouges and scrapers to turn one-off pieces "freehand", but now I would like to make a small series of spherical boxes, and need a more efficient way to accomplish that.

I would like to make a "ring scraper" for experimenting with. The only hollow tubular steel material I have at hand is cold-rolled steel tube in 50 mm dia. I am almost sure that this stuff is good enough for a scraper. But I would be really grateful for any advice about a suitable design for, and the proper/safe way of using such a tool.

Thank you in advance,

János

 

[loz]

Hi Janos,

Just buy a hole cutter ( smaller than your sphere ) and grind the teeth off it, and sharpen, work perfectly for spheres ( add a basic handle

 

[Tony Spear]

How do that work then?

 

[loz]

How do that work then?

any ring held against a perfect sphere will contact at all points of the ring,

thus if you hold a sharp ring against a rotating imperfect sphere it will cut it into a perfect sphere, its maths, try it it works, ( some side to side movement is required to get full coverage. )

I normally do them between centres, then rotate the ball a little and clean up again.

Loz

 

[János]

Hello,

Dear Loz, thank you for your help! I will try that hole saw trick. I would like to make 65 mm balls, so an 50 or 55 mm crown might suffice, I think. I should use a very slow speed for safety, as with such a long cutting edge engaged a catch at high speed would be tremendous.

Have a nice day,

János