Naration coming soon. You may need to download Quicktime
for Windows to view the above slideshow (.mov format)
Working the glass with foot power!
Now for the test, first phase at least, actually working and shaping the glass with foot power.
The first step was binding the glass blanks, little cylinders of glass, to the metal rod that would be the handle for working the glass in the lap. I used sealing wax this time instead of the canada balsam I used on the first lens. The sealing wax was heated in a stainless steal soup spoon over a stovetop flame. The sealing wax softens and then I heated the metal rod so that the wax stays warm a little longer. Then dabbed the rod into the wax then tapped it on the glass blank. The wax hardens fast and binds the glass to the rod quickly.
Then the glass was dipped in water and into the 220 grit then into the lap. Then a couple more times to full the lap about 1/2 full with a slurry of grit. Then the grinding starts. Sometimes I have to give the drill gear a little kick-start to get the treadle moving and spinning in the right direction.
The grinding starts at the edge of the of the glass blank and as it progresses the flat spot in the center of the blank shrinks and eventually the end of the glass blank is shaped into a spherical curved surface. Then the blank is detached, flipped and bonded back onto the rod and the other side of the blank is ground into another spherical surface.
The grinding of one side took 32 minutes to reach the complete spherical shape. The second side was shaped and now I am grinding it down until the two spherical surfaces meet at the outer edge of the lens. That grinding is taking a little while because the glass blank I used was a little too thick, but I am getting there. I slowed down a little to work on this video too. :)
September 6, 2012
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