A professional who operates gas furnace that heats metal gun parts to rustproof and impart decorative nonreflecting blue finish. Respnsibilities include:

• Sprays parts with steam to remove grease, grit, and dirt.
• Places parts in barrel of gas furnace and covers parts with mixture of bone chips and whale or pine tar oil.
• Closes furnace door and moves lever to rotate barrel.
• Turns gas valves and observes pyrometer to regulate temperature of furnace.
• Opens door after furnace cools, and pulls lever to tilt barrel and dump contents into sieve.
• Sifts parts from bone mixture and quenches parts in oil.
• Blows oil and chips from blued parts, using airhose.
• Examines parts to ensure shade and color conform to specifications, utilizing knowledge of heat-treating methods and metal properties.