Patent 1794361 (filed 25 March 1927) describes milling machine spindle and tool shapes using a steep taper. The patent was assigned to Kearney & Trecker Corporation, Brown & Sharpe, and Cincinnati Milling Machine Company. The patent wanted a taper that would freely release the tool and found that a taper of 3.5 in 12 had that property. The patent also used the keys and slots and a tail on the tool shank to prevent the tool shank from falling out of a horizontal mill's spindle while the operator connected the drawbar.