Over the decades, the rating of Machinist’s Mate (MM) has undergone myriad changes, including the creation of over 20 service ratings and numerous mergers with other ratings, such as the merging of the Boiler Technician rating with the MM rating in 1996.
Today, in addition to the MM rating, there are three service ratings: Machinist’s Mate Auxiliary (MMA), Machinist’s Mate Nuclear Power (MMN), and Machinist’s Mate Weapons (MMW). MMs work with steam power and systems that derive electrical power from steam turbines; MMAs are tasked with maintenance and repair of internal combustion diesel engines, damage-control systems, and a host of environmental systems; MMNs are the experts in nuclear-powered propulsion; and MMWs keep launching and firing systems in a state of readiness, as well as handle organizational maintenance of small arms (and ammo) and underwater ordnance.
Sailors wishing to pursue the MM rating begin as Firemen apprentices and attend the Basic Engineering Common Core School in Great Lakes, Illinois, followed by three-and-a-half weeks of Advanced classes. At that point, MMs will be assigned a strand to determine which service rating they will be working in; MMs slated to serve on submarines will attend the Navy’s Submarine school in Groton, Connecticut.
There are a couple of aspects of a job in MM rating that new recruits who are in the process of choosing a career path might want to consider. One is that over a twenty-year career in the Navy, Sailors who serve as Machinist’s Mate typically spend around 70 percent of their time assigned to fleet units and just 30 percent assigned to shore stations. Another is that many tasks performed by MMs can be very physically demanding, and sometimes require working in confined, hot, and noisy environments.