My Mirror Grinding Project

2 Hours Grinding!

© NeoDinian, 2006

Here's what I have after 2 hours of grinding with the 80-grit. This is not 2 hours in a row, but rather 2 hours total. I think I was grinding in 15-30 minute shifts over a few days. So far, my center depth (Sagitta) is .067. My target depth is .0833.

In this picture, you can see that the tool has ground down around the edges. This is from the type of stroke used for the grind. It's called a "Cordial" stroke, which is really just offsetting the blank about 40% to the edge of the tool, and grinding a straight line along the edge of the tool. While doing this, randomly rotate the blank and move around (or rotate) the tool. This helps to "Hog-Out" the center of the mirror as you grind.

As my blank gets closer to the target depth in the center, my stroke will move inward on the tool from 40% overlap to 30%, and so on, until I am grinding directly across the center of the tool. This will start to work the rest of the blank into the sphere shape I'm needing. By that time, I should be at, or pretty close to my target depth, and the whole tool will show wear.

I'm estimating I need about another 2 hours of grinding to get the nice sphere. At that time, I can then move on to a finer grit, and a different type of stroke to continue my mirror.

Stay tuned!