Visit your local Home Depot or Lowes and purchase a bimetal hole saw. The outfit will have a arbor with a 5/16" drill bit in the center and acts as a guide for the actual hole saw. The hole saw's are available in a variety of sizes that thread on the arbor. I recommended the bimetal just in case you would use it in mild steel or aluminum in the future. Hope this helps. Rollcaster.........