A professional who laps valves against valve seats to produce gastight fit, using powered tools. Responsibilities include:

• Applies lapping compound to bearing surfaces of valve and seat.
• Inserts valve stem into valve guide and positions valve against seat.
• Engages holes or slot in top of valve with projections in powered rotary tool (valve grinder).
• Presses and rotates valve against seat, using powered tool.
• May test valve by connecting chamber to hydraulic or pneumatic pressure and observing leaks.
• May rotate valve against seat, using handtool.