[ATM] Optical flats

["Francis J. O'Reilly" <foreilly@verizon.net>]

I have taken the day off from work and studying for a professional licensing exam to resume work on my seven inch optical flat project.

I last pushed glass on this on April 15, 2007. My notes revealed that I was ready to move onto 320 SiO. Today I completed sides A, B and C with the 320. I am now taking a break before turning over the blanks to work on sides D, E and F. It is back breaking work to be sure.

I grind each side for fifteen minutes against each other side alternating so that at the end of the process, each side has had 30 minutes of contact with each other surface, 15 minutes on top and 15 minutes on bottom. The total time grinding for each surface is one hour with 30 minutes on top and 30 minutes on bottom. It takes a total of 90 minutes of true galss on glass time to complete the three surfaces. I allow additioanl time because, I know that it takes time to clear swarf and to recharge the grit. The reality is that I allow two hours to complete 90 minutes of grinding.

I am glad that I am keeping scrupulous notes on my progress. The notes have been helpful.

I bought the glass from Newport Glass. The service and turn around time was excellent.

When I started, I began with 500 SiO. I quickly found that certain marks left on the blanks during the manufacturing process were too deep for the 500 SiO to grind out, I backed up to 320, still no luck, I then went back to 220 and using a seven inch plate glass tool that I had lying around on all of the six surfaces, I eventually removed all of the marks.

I vow never to be lazy and try to shortcut the grinding process again. A lazy man's load makes two.

Happy fourth of July to all in the US. Enjoy your day to everyone else.

Anyone in the military, join me in a salute to our flag.

Francis J. O'Reilly
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