Abstract: A tube cutoff machine for cutting a tube to precise lengths, which tube may be exiting from a tube mill at relatively high speeds. The tube cutoff machine includes a frame which supports a carriage for generally linear reciprocal movement parallel to the linear path of movement of the tube, the carriage in turn supporting a tube shearing apparatus. The carriage is reciprocated by a crank drive mechanism and additional connecting structure, which insures that the carriage will move at a constant linear speed for a duration of time sufficient to shear the tube as the carriage moves from a first location to a second location. The additional connecting structure includes a bell crank having an intermediate portion which is pivotally secured to the carriage, one end of the bell crank being secured to an end of a connecting rod of the crank drive mechanism, and the other end of the bell crank being provided with a cam follower which is caused to engage a stationary cam carried by the frame.