Brown & Sharpe #9 ER40 Collet Chuck. Now you can use 3/4" shank mills, drills, boring bars, and so on in your Brown & Sharpe #9 taper machinery, such as Bridgeport M head, Clausing, and several other older milling machines and lathes. No need to pound on your draw bar to remove your BS9 collets anymore, just unscrew the ER40 collet nut and switch collets. Much easier and quicker to switch tooling, and less wear and tear on your expensive spindle bearings.