Machinist's mate

Machinist's Mate (or MM) is a rating in the United States Navy's engineering community.

Description

According to Borce Blazevski, the job of an MM is to "operate, maintain, and repair (organizational and intermediate level) ship propulsion machinery, auxiliary equipment, and outside machinery, such as: steering engine, hoisting machinery, food preparation equipment, refrigeration and air conditioning equipment, windlasses, elevators, and laundry equipment. Operate and maintain (organizational and Intermediate level) marine boilers, pumps, forced draft blowers, and heat exchangers; perform tests, transfers, and inventory of lubricating oils, fuels, and water. Maintain records and reports, and may perform duties in the generation and stowage of industrial gases." -- NAVPERS 18068F

Machinist's Mates generally fall into one of two roles:

Propulsion Mechanics

The core job of an MM is the engine room. A mechanic's job in the engine room is to operate the steam plant that provides propulsion, electric power (along with Electrician's Mates), potable water, and service steam to the ship. MMs operate the boilers that generate the steam (this job was previously done by Boiler Technicians, but the BT rating merged with Machinist's Mates in 2000) and use it to operate main engine (propulsion turbines), turbogenerators, distilling units, and various auxiliary turbines.

Machinist's Mates responsible for the propulsion plant are found in Machinery Division (or Main Engine Division in some ships), commonly referred to simply as M-Division or M-Div. On surface nuclear ships, propulsion mechanics are found in Reactor Propulsion Division (commonly still referred to as M-Div), Reactor Mechanical Division (RM), and Reactor Laboratories Division (RL). The USS Enterprise is the exception, in that M-Division is still part of Engineering Department, as opposed to Reactor Department.

Auxiliary Mechanics

The other major place to find Machinist's Mates is in the Auxiliaries Division of Engineering Department. Mechanics in this role work on mechanical equipment outside of the engine rooms, to include the dishwashers in the galley, laundry machines, AC&R (Air Conditioning and Refrigeration) units, O2/N2 (liquid oxygen and nitrogen) units, lifting and hoisting gear, and other equipment as designated by the Engineer Officer (Chief Engineer, or CHENG). Members of "A-Gang" may also help DC Men, Gunner's Mates, or other ratings.

Nuclear Mechanics

Some MMs are qualified to work on nuclear propulsion plants. They are designated as MMN (Machinist's Mate Nuclear), though the N is generally only used for the purposes of billiting and advancement exams. These mechanics go through a rigorous training program consisting of fourteen weeks at the Nuclear Field "A" School, twenty-four weeks of Naval Nuclear Power School, and twenty-four weeks at one of two Nuclear Power Training Units (prototypes). This course of instruction is commonly referred to as "the nuclear-power pipeline."

MMNs earn a 3385 NEC (surface) or 3355 (submarines) upon completion of prototype. Along with the normal duties of a propulsion mechanic, they are responsible for the operation, maintenance, and repair of the auxiliary equipment in support of the naval reactors under their care. Later in his career, the MMN will qualify his/her Senior In-Rate watchstation (Chief Reactor Watch for surface MMNs in Reactor Mechanical division, Chief Machinery Operator for those in Machinery Division, and Engine Room Supervisor for submariners) and receive the supervisory NEC of 3395 or 3365 as appropriate.

Additionally, some MMNs are designated as Engineering Laboratory Technicians (NEC 3386 for surface, 3356 for submariners) following sucessful completion of an additional 13 weeks of training. ELTs are water chemistry and radiological controls experts for their commands. Upon qualification of one of the above-mentioned Senior In-Rate watches, they are awarded NECs 3396 or 3366.