Machinist’s Mate

Navy Machinist Mate (MM):
Career Details

Machinist’s Mates (MM) perform the operation and maintenance of steam turbines, gears for ship propulsion, and auxiliary machinery including refrigeration plants, desalinization plants, electrohydraulic steering engines, and air conditioning systems.

The Machinist Mate rating traces back to 1880, originally called the Finisher rate, and has evolved through various name changes. In 1996 the Boiler Technician (BT) rate merged with the MM rating.

MMs have a number of specialties:

• MM – Machinist’s Mate
• MM/SS – Submarine Qualified
• MM(A)(P) – Photographic
• MM(O) – Optician
• MM(SRE) – Ship Repair (Engine Operator)
• MM(W) – Weapons (formerly Torpedoman Mate)
• MML – General
• MM(N) – Nuclear (significant distinction from Aviation Machinist’s Mate AD)

To become a Navy Machinist Mate, certain requirements must be met:

• Member of the US Navy (US citizenship not required unless submarine volunteer)
• U.S. citizenship optional; no security clearance required
• Age 18–39
• No record of drug abuse offenses
• Normal vision and hearing
• ASVAB score: VE + AR + MK + AS = 188 OR VE + AR + MK + AO = 193

After successful completion of Boot Camp (eight weeks), candidates attend the Navy Machinist’s Mate Technical Class “A” School at Great Lakes, Illinois (nine weeks). This class covers:

• Technical documentation
• Mechanical theory
• Safety protocols
• Piping system operation
• Tool and equipment handling
• Maintenance management system
• Watch standing procedures
• Marine steam propulsion operation
• Preventive maintenance

MMN (Nuclear) candidates attend the three-month Nuclear Field Class “A” School and the six‑month Nuclear Power School, followed by the six‑month Nuclear Power Training Unit.

Pay is based on rank and length of service. Base pay ranges from $1,917.60 for an E-1 to $6,055.50 for an E-9 (Master Chief). Additional allowances and billet pay may apply.

MMs typically spend about 70 % of a twenty‑year career at sea and 30 % shore. Sea/shore tours typically last 3–5 years per tour.

Typical duties include:

• Align piping systems and operate ship boilers and steam turbines.
• Control turbo generators.
• Maintain and repair auxiliary machinery (steering engines, elevators, pumps, compressors, etc.).
• Operate and maintain desalinization plants.
• Maintain refrigeration plants, air conditioning systems, and galley equipment.
• Repair or replace valves, pumps, heat exchangers, and other components.
• Document and analyze machinery operating records.

MMs qualify for civilian roles such as HVAC technician, operating engineer, maintenance mechanic, and nuclear power plant technician. The United States Military Apprenticeship Program enables completion of civilian apprenticeships while on active duty.

What does a Machinist Mate do? They operate, maintain, and repair ship propulsion systems and auxiliary machinery.

What is a Navy Nuclear Machinist Mate (MMN)? A specialist who works on nuclear power generation systems aboard aircraft carriers and submarines.

What ASVAB score is required? VE + AR + MK + AS = 188 or VE + AR + MK + AO = 193.

How long is the training? Approximately nine weeks for a standard MM; military nuclear training adds 12 additional months.

How much does a Machinist Mate make? Base pay ranges from $1,917.60 (E‑1) to $6,055.50 (E‑9); nuclear specialists may be eligible for bonuses.