Vacuum Pan
To make the vacuum pan a metal lathe is used. I machined my pan from aluminum 6061 T6 plate stock. (very common in the metal world). I purchased a square piece of plate ( one inch thick for my 11" pan and a 1 1/2" thick for my 16" pan). The corners were cut off with a wood table saw. A cheap carbide tiped saw blade covered with lots of motor oil was used on the saw to do this operation. Wear a safety face shield for this operation!
Three blind 1/4"x 20 holes are drilled and taped in the back of the plate for bolting to lathe face plate. A spacer such as a washer is placed on each bolt between the face plate and the pan plate. I used 1/2" ball bearings for washers. Do not bolt directly to the face plate as this will distort the pan plate. Machine the pan 1/2" to 1" larger then the optical diameter of the Schmidt plate. On the front side of the pan the pan depth is turned to about .100" to .150" deep. The inside of the pan is the optical diameter of the Schmidt plate. In my case I machined a 1/4" seal rim around the pan. This can be less but I think the extra width of the rim gives a better seal also the 1/4" is covered by the Schmidt corrector cell which will cover any turned edge.
Pan seal rim l--l l--l<.030" high l--l l < .100" to .150" deep l l--l .250" wide l l-----------------------------------l l l l l Al 6061 T6 l< 1" to 1 1/2" l l thick l l l-----------------------------------------------l
In my next post I will talk about the vacuum valve and finishing the the plate. Bob Pfaff