One of the best ways is to use a hole punch. You need a 1 1/4 inch
size. Aircraft Spruce carries them. Here's a link:http://www.aircraftspruce.com/catalo.../knockout2.php.

Charlie

Charlie, I think you meant to type a 2 1/4 inch hole. 57MM equals 2.24
inches. Doug

Thanks for the correction. Fingers on the wrong key. I need to edit
better before punching the send button! At least the link was correct.