Step 7: Drill center hole for Porcelain socket
I highly recommend you test drill scrap wood and make sure the dimensions fit your socket properly prior to drilling your wooden base that you have chiseled into a disc. Also, I recommend drilling these holes in a drillpress so they are perfectly square, however it can be done using a hand drill if you are very careful.
Drill the 1.5" hole first:
The porcelain socket is just a bit smaller in diameter than 1.5". However, the socket that I bought was not perfectly round either, but a 1.5" hole allowed the socket to fit snugly. As you can see in an accompanying picture, you will want to drill a hole that is 1.5" (or a suitable size to snugly fit your socket if different) in the center of the base. However, you do not want the hole to go all the way through the base. The 1.5" hole should be drilled from the top of the base and should have a depth of approximately 1.75" so the hole leaves 1/4" of material on the bottom of the base. Although any 1.5" bit should work, I prefer a forstner bit because when drilled slowly, it creates a very clean hole and does not tear out any wood on the outside diameter of the hole.
If you find your porcelain socket is also malformed and not perfectly circular, do not worry, simply review how off your socket is from a circle and drill a second hole that takes off the extra wood to allow the socket to fit properly into the base. In my case, I only had to remove approximately 1/32" of additional wood. This is a very simple operation in a drill press.
Finish drilling hole with 5/8" diameter:
Next you want to drill a 5/8" hole through the center of the 1.5" hole through the bottom 1/4" of wood in the center of the lamp base. This 5/8" hole will go through the remaining 1/4" of wood on the bottom of the base.
Take out the set screw on the bottom metal part of the porcelain socket and then fit it into the wood base and make sure it fits properly.