Coasters I have been making coasters like these for years. This picture shows you all various ones using old used shot gun primers and used shells that could have been thrown away. I had to make custom made drill bits in order to sink them into the oak. The right one is an original before I developed using an adjustable circle cutter to make a groove in the wood and fill in with floor grout. The idea was for the grout to absorb the moisture off the cold glass instead of running down onto your table. Since these are done on a drill press, you will see the jig I had to make up to hold it in place on the drill table for safety reasons.