Taper thread cutting machine and method

Abstract

A machine for taper threading the end of a bar such as reinforcing bar used in concrete construction utilizes a power operated vice to clamp and feed the bar end axially into a rotary head which contains chaser tooling holders which open uniformly on the bar end as the head rotates. The rotary head is axially stationary but contains an axially movable key or linear cam which engages a readily removable transversely extending control rod assembly in turn moving the chaser holders. Axial movement of the power vice and thus the bar end at a controlled axial speed with respect to the rotary speed of the head moves the key to cause the movement of the chaser holders. The chaser holders in addition to supporting the thread cutting chasers also support ahead of the chaser an indexable triangular insert to pre-cone the bar end. To change the set-up of the machine for different bar sizes the control rod is removed and replaced, and a proper cutting speed for the bar is selected by adjusting the RPM of the head through a transmission. The extent of axial movement of the key may also be controlled to optimize the cycle time of the machine. In this manner all bar sizes may be threaded in a single pass and set-up from bar size to bar size is accomplished quite simply in a short period of time.