Re: [CAD_CAM_EDM_DRO] Re: Plasma Spraying

Leslie M. Watts wrote:

>Jerry,
>
>Is this a typical South Bend lathe bed?
>
>If so I can understand your reluctance to tackle
>scraping the v-ways. Actually I should say hand grinding, as the ways are
>hardened and cannot be
>scraped conventionally.
>
>

I can attest to the difficulty of this.

>Nevertheless I have seen many redone using prussian
>blue, a pencil die grinder, straightedges, and a polymer casting replicated
>from the ways used as
>a guage. The casting is made from an unworn area
>of the bed, typically from under the headstock or
>near the tailstock.
>
>

When using conventional scraping tools, you get the benefits of "automatic
generation", the way 3 surface plates are lapped together to get flat
surfaces.
The grinder approach tends to create divots! I did this as a 2nd step
(using the
existing tailstock ways to guide a grinder as the first step) and am now
doing
the 3rd step, finishing the ways by lapping with bench stones. VERY
SLOW!!!!!

>I have also seen polymer materials used to build up
>lathe ways.
>
>
>

<snip>

>Also keep in mind that if tools are on the centerline,
>even quite worn v-way beds can still give accurate
>results when turning.
>
>

Up to a point, yes. I didn't actually test my machine (as the idiots
temporarily
lost the chuck) but calculation indicated a worst-case error on a 1" bar
would be
.016" in radius from the least to most-worn part of the bed. That would
cause a .032" diameter change in a barrel shape! Not acceptable! The
problem
is that cutting down forces concentrate on the front inverted Vee,
causing it to
have .016" vertical wear, while the back, flat way had only .003" or so.
If both ways were worn equally, the error would have been vastly smaller.

Jon