I looked high and low for some brass and this is all I had. However, this will be more than enough for what I need. The small piece on the left and the long piece on the right are 1/2" diameter. But I'll need to take a clean-up cut on them both, which will bring the outside diameter down a little smaller. This is why I choose the undersize end mill earlier.
 

I'm using some 60 minute epoxy so I can take my time installing each one. After mixing the epoxy, I placed the insert on a steel drive punch to make it easier to apply the glue using a small paint brush. This method kept my fingers much cleaner so I didn't get it all over my wood pieces.
 

Last I used my milling machine to chamfer each side of the inserts by hand. Now that the brass inserts are finished, I'm going to add some small rubber feet to the bottom of each board.
 

I looked at everything that I had to use as rubber feet but couldn't find anything that was small enough. Then I looked online for some, but didn't see anything I really liked there either. So that measn I'm going to make my own rubber feet out of some rubber that was used as packaging that I saved from years ago.

This angle rubber has two thickness': one is just under 1/8" and the other is close to 3/16" (arrows). The thicker stuff should work great for what I've got in mind but I'll have to cut them out first.