centreless grinding was Re: Bar stock

Ian,

I haven't seen the three wheel technique, but I can see how it might
make the lobed form. The 2 wheel and "blade" rest that YethDear
described is what I have seen. My understanding of the 2 wheel type
is that is DOES make the bar "perfectly" round.

Is this an our-side-of-the-pond vs. your-side thing<G>, or an older
vs. newer?

Comments?

Ballendo

--- In CAD_CAM_EDM_DRO@y..., "Ian Wright" <Ian@i...> wrote:
> Hi John,
>
> Merry Christmas...
>
> Centreless ground means that it is ground without being supported
at each
> end by fixed centres. The way they do it is by running the bar
between three
> grinding wheels arranged in a triangle, so, as it goes through, it
is ground
> pretty round. Having said this though, it can't be relied on to
actually be
> round and this is why they specify it as centreless ground. The
most common
> fault with it is that the steel develops 'lobes' and what should be
round is
> actually more of a slight triangular shape with very rounded
corners. As the
> three grinding wheels are fixed, you will always get a constant
diameter but
> this may not always be exactly concentric with the centreline of
the bar -
> like the piston in a Wankel engine.
>
> Ian