[TheForge] Re: Timken Case Hardening was File Making

[Bruce Freeman]

I'm not sure what tolerance you can achieve, but spheres are routinely
ground out of rocks using a clever apparatus.  Take two pieces of
pipe, angle them up, maybe 120 deg. between them.  Leave a space for
the rough sphere at the vertex.  So rough sphere is held by two pipes.
 Now rotate the pipes, grinding material at ends of pipes.

In fact, the pipes point down, but that has to do with grit feed and
waste, not with the general procedure.

Real marble marbles used to be made a different way.  Raceways in a
pair of cast-iron wheels - CUBEs of marble placed in raceways
(probably wet - not sure).  Rotate one wheel. Result: marble marbles.
Marble is pretty soft.  Don't try this with agate.

Bruce
NJ

On Thu, Mar 20, 2008 at 9:17 AM, Andrew Vida <osan at netlabs.net> wrote:
>
>
>  Mike Spencer wrote:
>
>  > Okayyy, so how do you -- er, they -- make spherical bearing balls?  I
>  > recently had some enlightenment from the list about making flat things
>  > using three pieces and a scraper.  So how you you make spherical
>  > things to close tolerance?
>
>         There are high precision grinders that will get you 98% there.  I would
>  imagine that the rest would  be lapping the pieces into each other.
>
>
> _______________________________________________
>  Manage membership or unsubscribe at:
>  http://mailman.qth.net/mailman/listinfo/theforge
>  theforge mail list group photo site is
>  http://www.photoaccess.com
>  Login:  blacksmithblacksmith at hotmail.com
>  password:  anvil
>  ___________
>
>
>



-- 
Bruce
NJ