RE: ATM Scratches during fine grinding

[Bob Prabowo <BOB@bahana.co.id>]

Hi Poul,

Since you're still in the early stage of fine grinding I think you should
not worry too much about the scratches. 

But to prevent more scratches in the future, here's what I suggest you to
do:

1. Bevel the edge of the tiles. Sharp edges can chip easily and the chip
might get in between the tool and the mirror. Though some may disagree with
this, I think it would be better if you bevel the edges of all the tiles,
not just the tiles at the edge of the tool, but the whole tiles. Hopefully
this will reduce the chance of the tiles from chipping during grinding. 
When I had the same problem and posted my problem to the list, someone
suggested that I bevel the edge of the tiles. I followed this suggestion and
no more scratch appear.

2. Maybe you must seal the tool completely since your tool is made of wood.
Grits might trapped in the wood grain. Seal or cover the bottom and also the
edge of the wood disk with cellotape.  My polishing tool is made of plywood.
I cover the edge and the bottom of the tool with packing cellotape. I don't
know what it is in English, but it's the wide brown cellotape used for
packing. 

3. Don't forget to clean your hands, and pay special attention to your
fingernails, under the fingernails. I always use an old toothbrush to clean
my fingernail. It's a really good place to hide for abrasives.

4. If you're wearing a ring (wedding ring, any kind of ring) take it off. 

Hope this helps
Good luck

Bob P. Sumitro
Jakarta, Indonesia

visit my still-under-construction astronomy and telescope making page:
http://www.geocities.com/CapeCanaveral/Hall/2670/