I made myself a handle and a mount for the mirror and tool. These were fixed onto the glass with pitch and the tool block which had an aluminium rim was fixed to an old table by three screws, just loose enough to allow the tool to be rotated anti-clockwise after every 12th stroke clockwise (one per second) of the mirror, which in theory made up one full rotation.

A box was made up so that both mirror and tool could be reversed to allow for correcting purposes

I then made a start on grinding (hogging) the mirror. I did a test mirror first as I was sure to make lots of errors along the way (and I certainly made a good few!)

Starting with 80 grade carborundum powder, I spent 4 1/2 hours, 15 minutes at a time ( to allow the glass and me to cool down ). One thing that I knew that might be a problem was that the glass I was using was thinner than it should have been, so I tried to keep it from distorting by not working it for too long. I finished each session with 2 minutes using 220 grit. This helped to show were the most wear was taking place and improved reflection when testing.

The knife edge test was done using the Foucalt method. By wetting the mirror enough light was reflected to allow the focal length to be roughly found.