On Sunday (02/03/2008), I did about 60mins of grinding mainly using the 1/3rd chordal strokes with 1-1.5" offsets. I was hoping to make the tool flat or at least almost flat. I was disappointed when after cleaning and drying the two surfaces, measurements indicated that the tool was still concave and the mirror still convex. My rough measurements show that the tool is 1.5-1.8mm deep. This is based on various drill bits that I tried sliding under a straight edge placed on the tool. Again these are very rough calculations. The mirror blank seems to be a lot more convex and based on the current progress, I am thinking that the tool is likely to become flat first and then the mirror. Looks like I may have to work several more hours with the #36 grit to make the two surfaces flat.
I was initially thinking that I will keep the 12" mirror blank aside and concentrate on making a 8" mirror. However, as I do not have the tool blank for the 8" yet, I decided to work on the 12" mirror since I had some time. My plan is still to start working on the 8" mirror and complete it and then come back to the 12" mirror.
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