SOLID BRASS TURN KNOB LAMP PART SWITCH 4-36 THREAD Review Posted on February 27, 2019 By DaughterSeaUrchinTagged Hardware, Knobs, Tools & Home Improvement Solid brass turn knob with 4-36 threaded hole (standard socket thread) to turn your lamp off/on. ( 3/4″ long- the head is 1/2″). We sell for less in lots of 20, but you’d need to buy from that listing.