Class #1
Randolph Center Sky Clock -


  2005-2006 Mirror Making Class & Workshop 'Official Page'.

Class# Pics and Info
During Class

Rough Grinding
It wound up being a beautiful day, so some of us worked outdoors.  This was my workstation.  The wire spool table was very stable and worked very well.  Great height, too.  Click picture to enlarge

Here's a close-up of my grinding tool.  It's just a 8" disk, with hexagonal tiles mounted on it.  You can also see the turntable that Tom Gorka sold while at the class.  It was nice to buy it, as I can concentrate on grinding at home, instead of worrying about making one.  Click picture to enlarge
Here's a close up of my 8" mirror.  It's got a spherical shape, now, but is still far from being a polished surface.  It has only been through 60 grit and 80 grit so far, so it's got a texture similar to being sandpapered, only with pits instead of long scratches.  I have about 9+ hours of fine grinding left to go, before I get to the polishing stages.  Click picture to enlarge

Overall, I found the class to be very exciting.  Tom Gorka, Ken Slater and Jay Drew were very helpful, and guided us well.  Tom also put an extra bit of sparkle in our smiles, by showing us how our mirrors could already collect light into a point with a wet surface.

Post Class Here is me working on grinding the mirror.  It looks like I'm really flying, but in reality, I'm only working at about one complete cycle every 1-1.5 seconds.

Click image to enlarge.

Here's me grinding, but I paused for a moment, so that you could see a little more detail.

Click image to enlarge.

It's important to keep checking the Sagitta, or depth, of the spherical shape of the mirrror.  Mine needs to stay right at 0.083" lower in the middle than at the sides.

Click image to enlarge.

Here's another more recent shot of the mirror.  You'll notice the black grid lines on the mirror.  These are from my 'Sharpie Test'.  The 'Sharpie Test' is where a grid is drawn with a black Sharpie, and then you grind for a minute or two, to see whether the mirror and tool are making good contact.  If the grinding lines are nice and even, then you have good 'contact' and therefore a sphere.

Click image to enlarge.

Here is a pic taken through a 10x eye loupe, like a jeweler would use to check out jemstones.  As you can see, there are some bigger pits at the center of the pic.  I tried to get rid of all these pit marks, but they kept returning.  Advice from Ken was that it's likely that there is some larger grit in with the 120 grit, making these pit marks.

Click image to enlarge.

Here's what the mirror should look like, taken through a 12x eye loupe.  You'll notice that the texture of this mirror pic is much more even.  Looks like I'm ready to leave 120 grit, and move to 220 grit.

Click image to enlarge.



(c) 2007 by the Randolph Center Stargazers
Site was last updated on: 01/06/2006