New old stock Heavy Delta Rockwell Cast Iron Control knob. Knob is approximately 3" diameter, is about 1-1/2" in height. Bore is just under 1/2" and looks like a press fit, should be enough material to drill out to 1/2" and even carefully drill and tap for a set screw. Nice heavy knob, great for machine restoration, or other projects. Delta part number 426-06-027-5004.