Re[2]: ATM "Tubular" Grinding Tools

[Dwight Elvey <elvey@hal.com>]

Hi
 I've been trying several different things while
hogging out my 14.5". I tried a glass jar and although
it seemed to work, the mirror glass had a course
surface and looked to be chipped. My best tool so
far is a plaster tool of 50% diameter with two rows
of tile mounted edge on around the edge.
 I've given some thought on the use of steel pipes.
Many have said it works well but tends to leave deep
scratches that require more work to get out. I suspect
this is caused by the grit getting embedded into the
metal. When cutting things like holes, copper is often
used. The intent here is to remove as much glass as
possible. The soft copper will hold the grit making
it more like sawing than grinding. This problem of
holding the grit can also be a problem with the various
tools using ceramic. If the ceramic has
small bubbles and the holes are similar in size to the
grinding grit, some may get caught in the tool, causing
scratches.
 Part of the increased speed in removing glass is
from this sawing action and part is because of the
increased preasure per square area. The biggest problem
I'll seen with sub-diameter roughing tools is that
one has to watch the curve closer. If one is doing
this without checking the curve regularly, you'll
be in for a suprise. At least that is my limited experience
so far.
Dwight