Re: ATM Hogging Out

[Hermit <klowther@cisnet.com>]

Bill Kelley wrote:
> 
>   To all:
> 
>   It occurred to a young friend and I, as we were hogging out an 8 inch
> mirror tonight, and starting with two 8 inch blanks, that perhaps the
> chordal stroke that everyone seems to use for hogging out is not the fastest
> way to dig a hole in the center of the mirror.  So we put the mirror on the
> bottom, sprinkled 80 grit, and spread it around with the tool.  Then our
> hogging stroke consisted of pressure on the edge of the tool sweeping back
> and forth over the center of the mirror with about a 4 inch stroke and heavy
> pressure on the edge of the tool.  As the edge of the tool was being driven
> into the center of the mirror, we continued the usual rotation of the tool
> and walk around the barrel.  This dug a hole very quickly; much faster than
> the traditional chordal stroke mirror on top.  To bring the rough figure
> back to a sphere; every third charge of grit, tool still on top and heavy
> edge pressure, we started our strokes with the tool concentric on the
> mirror, and the edge of the tool stroked just across the center of the
> mirror.
> 

Sounds like you simply are doing an inverted chordal stroke.  I don't
see why it would be any faster.  I wondered about this technique a few
months ago.  I think it was Frank Ward who said he used it.  I don't
remember the context of the thread.   I think I "thought" of it as a
grit saving technique since the 'hole' was on the bottom and you were
less likely to drive the grit off of the work piece.

-- 
Ken Lowther
Youngstown, Ohio
http://www.atmsite.org
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