An employee was kicking out a piece of pipe. As the pipe kicked out, the two jack cylinders from the turn rolls were not fully retracted, causing the pipe to knock the turn rolls over. As the employee placed his hand on the frame and was attempting to re-center the turn rolls, the frame of the turn rolls slid off the jack cylinders and pinched his left middle finger against the frame assembly and the floor plate. As a result, his left middle finger was partially amputated.