[legswilly (Werner)]

I got some square glass from Sydney and wanted to cut the rounds with a glass cutter as shown on youtube. Would not work with the cutter I bought and homemade tools. Got my grinding/polishing turntable built and cut the rounds on the turntable. First one was not too bad and the next 2 turned out OK. Chamfered them and I thought the polishing should be OK to do.

I read about grinding/polishing flats in Making your own telescope by Allyn J. Thompson. With the three blanks method and float glass, 600 grit is recommended, because it should be reasonably flat. I bought an optical flat and calibrated a homemade spherometer and it gives me a difference of appr. 0.0005". That is over 75mm, I only got a 80mm optical flat. So I thought that is not too much.
I have never polished glass and what happened is that after a very few rotations (4 rpm) the top blank seized on me. I used plenty of water in which I had mixed the 600 grit. It was like I was wringing precision steel flats together. Very hard to shift. Has to stop the turntable and slide it off. On looking at the blanks after cleaning, some dull areas showed where it was ground. If I would keep going, I could not hold onto it, too much grabbing.

What am I doing wrong? Is it not possible to do it this way? Would I have to make a lap and selectively grind/polish it flat?
Sorry for the long post.