The MM Rating
Orginally established as the Finisher rating in 1880, then renamed Machinist in 1884 only to be reverted back to the Finisher rating in 1895, then ultimately given the name that stuck, in 1904, Machinist's Mate. Furthermore, the Boiler Technician (BT) rating merged with the Machinist's Mate rating on October 1, 1996.
Machinist's Mates (non-nuclear) operate and maintain steam turbines and reduction gears used for ship propulsion and auxiliary machinery such as turbogenerators, pumps and oil purifiers. They also maintain auxiliary machinery outside of main machinery spaces, such as electrohydraulic steering engines and elevators, refrigeration plants, air conditioning systems and desalinization plants. They may also operate and maintain compressed gas producing plants. (Nuclear Machinist's Mate Information)
Machinist's Mate (MM)
The duties performed by MMs include aligning piping systems for oil, water, air and steam, and controlling the operation of ship boilers and steam turbines used for ship propulsion and service systems. They control the operation of turbogenerators used to produce electrical power.
MMs clean, adjust, test and perform other preventive maintenance on a ship's boilers, main engines, turbogenerators, and other auxiliary machinery including steering engines, elevators, winches, pumps and associated valves. They operate and maintain desalinization plants (distilling plants) to make fresh water from sea water, and maintain refrigeration plants, air conditioning systems and galley equipment.
MMs repair and replace valves, pumps, heat exchangers, compressors, steam turbines and hydraulic or pneumatic control devices. They also maintain and analyze machinery operating records and reports.
Qualifications, Interests, and Working Environment
Machinist's Mates should have clear speech, physical stamina, manual dexterity and the ability to work with others as a team. They should know how to use common hand and power tools and enjoy working with mechanical devices. Other helpful characteristics are resourcefulness and an interest in learning new ideas and skills.
Normal hearing is required. Machinist's mates work within the hull of a ship in fire rooms, boiler rooms, engine rooms or shops. These locations are sometimes hot and noisy. MMs may be required to perform some heavy physical work. They must be able to work closely with others and, in some cases, with limited supervision. MM ASVAB Test score requirements.
Credit Recommendations
The American Council on Education recommends that semester- hour credits be awarded in the vocational certificate or lower-division bachelor's/associate's degree categories for courses taken in this rating on machinery maintenance, blueprint reading, air conditioning and refrigeration.