Cool Sprocket Cover!

I took the sprocket cover off a while ago and have been trying to decide what to do with it as far as cool vents. After a light bulb type idea went off in my head I came up with this...

First I found the relative center line with a pair of dial calipers and marked it. Then I used a compass to draw the lines moving outward. I measured with the calipers and marked equally spaced lines to set the compass.

I decided to use a .250 endmill to drill the holes and wanted the distance between the holes to be at least half the diameter of the hole. So I measured out .125, set my compass and marked all the lines where the holes should go.

I set it up in the Bridgeport and away we go!


Since it has a very small tip I used a starter drill to pinpoint where I was going to drill. That's all I did with it, since I was using an endmill I didn't have to have a pilot hole.
Milling...

After all the holes were drilled


Then it was off to the buffing wheel!
The polishing didn't come out as well as it could but I used red ScotchBrite, then 600 grit, then 1000, then the buffing wheel.