What are MIL Grade (MIL-Spec) Connectors?

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If you are in your engineering career, at least once in your lifetime you will come across the MIL grade connectors which are also called MIL-Spec, MS, or Military standard connectors. Earlier they were known as Army or Navy connectors as they were designed by the military for their aeronautic appliances and preemptive services. 

They are now standardized to be used in military applications that are used in harsh environmental conditions including oil & gas, marine, aerospace, etc. These connector types are specially designed for their durability as they are going to be used in the devices that work in extreme environmental conditions and one loosened thread may cause huge damage to the device and the people working around it. The connector designs vary for different applications and can be chosen according to the extreme environment, corrosion, vibration, dirt, humidity, etc. 

A MIL-Spec connector is designed with a mating pair- a plug and a receptacle. The pair need to match with the male and female contacts which are also known as pins and sockets respectively. Usually, phosphor-bronze or beryllium-copper alloy are used to make a connector which is best suitable for making electrical connections. To enhance the conductivity and make it corrosion free, it is then plated with a metal like gold. 

A MIL-Spec connector is comprised of various parameters like its number, size, contact coupling methods, terminals, and shell specifications, and to know more about your connector type, you must be aware of all these parameters. 

Contacts

Contacts are the conductive portion in any connector that is used to transfer electricity. The number of contacts is equal to the number of conductive elements present in a military connector. When a connection is formed between two types of contacts either they are pins or sockets, these conductive elements are used to form the electrical path between them. 

Different Types of Couplings

Various types of couplings are available in the connectors. These couplings are:

  • Threaded Coupling
  • Bayonet Coupling
  • Breech Lock Coupling
  • Quick Connect or Spring Rack Coupling
  • Ball Detent Coupling

Connector Shells and Terminals

The main covering over the connectors that protect them from corrosion is known as the “Shell”. Mostly, aluminum is the material that is used to make a shell that is further plated or anodized so that it creates a protective shield over the connectors and protects them from corrosion issues.  

The connector shell is available in various sizes and shapes depending upon the requirement. They are also available in various styles like:

  • Straight plug
  • In-line receptacle
  • Cable mount receptacle
  • Wall mount receptacle
  • Box mount receptacle
  • Dummy receptacle
  • Jam nut receptacle
  • Solder or weld-mount receptacle
  • Thru-bulkhead receptacle
  • 90° Plug

For circular connectors, the shell is available in a cylindrical shape in which the diameter increases according to the size of the connector. The minimum diameter size for a cylindrical shell for a circular connector is 0.375″. 

Terminals are the class of connectors that connects with various types of conductors for making an electrical connection. Crimping and soldering to cables are the two methods used to terminate terminals.