i used a hole saw, as long as you keep it level with the metal it cuts ok, anything crooked and the hole saw likes to jam up, i used a 2 inch one for the small guage and a 4.5 inch one for the speedo and tach, had to file the 4.5 out because they require 4 5/8 hole , but i couldnt find a 4 5/8th hole saw