A professional who sets up and operates battery of ball-truing machines to grind bowling balls spherically to size and smooth them preparatory to finishing and polishing. Responsibilities include:

• Installs conical grinding rings on opposing spindles and adjusts clearances and angle of cut, using wrenches and gauges.
• Places rough cast ball on holding pad between grinding rings and turns valve to start cooling water to flow over ball.
• Starts machine and moves dial pointer to preset running time cycle on each quadrant of ball.
• Removes ball from holding pad and gauges it with ring or calipers and rule to ensure specified size tolerances.
• May mark imperfections on ball to be drilled and plugged, using crayon.