Connector Graphic

Special Connectors for Military and Aerospace Hardware

Lots of the equipment I've worked on over the years has various types of mil-spec connectors on it. I've got good sources for these, locally, and I've also got all the crimping tools and other goodies to offer small-quantity fabrication of custom cables.

Please feel free to E-mail me with your specific needs.

Because of the size of the 'How To' section below, the navigation table is placed here.

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  (Last Update: 21-Sep-13)

How do I choose the right connector for my gear?

Before you can choose the right connector, it is important that you know some basic connector terminology.

Cable Clamp: As its name implies, a screw-on piece that attaches to the rear of the endbell, and provides strain relief for the incoming cable or wire bundle.

Coupling ring: The ring around the outside of a plug-style connector. Secures a mated pair together and prevents separation due to vibration or other mechanical factors. Can have either screw threads or a 'Bayonet' style of securing.

Crimp Pin: A connector pin, shipped in loose pieces with the connector body, that is designed to be crimped onto the end of the connecting wire using a special tool. It is then inserted into the connector body itself with another specialized tool. This type of pin is usually removable and replaceable.

Endbell: The portion of the connector that makes up the body. Screws onto the backside of the barrel. Comes in either one-piece or split arrangements. May also be called a backshell.

Front Release: A type of connector pin (crimp-style) that is removable from the connector's insert by pushing a special tool through the front of the connector to release the pin in question. The pin is then removed by gently pulling on its attached wire.

Insert: The molded portion of insulation that fits inside the shell and actually supports the connector's pins. The insert can be either resilient or hard depending on the connector type. Resilient inserts are most often found in 'E' (environmental) series connectors to aid in waterproofing the connections.

Rear Release: Same as Front Release, except that the extraction tool is inserted through the back (wire) side of the connector.

Shell or Barrel: The portion of the connector that holds the insulating insert.

Solder Pin or Solder Cup: A connector pin that is fixed within the body of the connector, and cannot be removed. The wire is attached by soldering it to the back side of the pin.

Connector Type Numbering

A full catalog of every mil-spec and aerospace connector made would take up a load of phone book sized volumes. Fortunately, many types of military surplus equipment use the well-known 'AN' or 'MS' style cylindrical connectors based on one of two military specifications.

MIL-C-5015 applies mainly to connectors used in older equipment. This specification covers a series of cylindrical connectors that range from less than an inch in diameter to nearly three inches, and contain from 1 to 100 contacts. This series has been in use for decades, and its numbering system has remained essentially unchanged at its core.

Distinguishing features of this series include large, prominent male pins or female contacts and screw threads for coupling, either 'coarse' or 'fine.' The 'coarse' threads often take the form of very prominent grooves cut into the outer receptacle shell.

MIL-C-26482, Series 1 and Series 2, covers a line of newer connectors that have been dubbed 'miniature cylindrical.' Their physical size is in the same range as the MIL-C-5015 series, but the number of contacts only goes up to 61. They do come under the 'MS' prefix part numbers, but are also known by prefixes such as 'PT,' 'KPT,' 'KPSE,' and others.

The 26482 specification connectors also have a couple of options for their pins. They come in both non-removable solder cup and crimp-style removable. Of the pair, the crimp style are more reliable under some conditions, but they are also more difficult to deal with as they require specialized (and usually expensive!) crimping, extraction, and insertion tools to deal with their pins.

So where's the number? If you examine the connector's insert or shell closely, you will likely find a type number. Those on the insert are typically two digits or two digits and a letter, a dash, and then two more digits followed by a letter. Some examples would be: 28-21S or 14S-5P

In either case, the first pair of digits represent the shell size code. The second pair indicate the contact arrangement, and the last letter in the string indicates whether the connector is a 'Plug' or 'Socket' style. A connector with visible male pins will always be designated 'P' in the last position, whereas a connector with female pins will always be designated 'S.'

Some distinguishing features of this series include small pins, gold plating on said pins, and the use of a 'Bayonet' style locking ring instead of screw threads.

Part Number Examples

Let's look at a typical pair of numbers for a mated connector pair in the 5015 specification. First, the receptacle, typically mounted on the chassis of the equipment.


The first pair of characters, MS, indicates the connector series. This can be either a standard designation or something proprietary to a specific manufacturer. If it's mil-spec, though, it will almost always be MS.

The four digits following the series, 3102, indicate the physical connector type. For the 5015 spec, these are as follows.

3100 - Wall-Mounted Receptacle. Designed to carry wiring through a bulkhead or wall. Provides strain relief for the wire bundle.

3101 - Cable-connecting plug/receptacle. These are receptacles or plugs with no mounting flange. They are designed to be used on extension cables. Strain relief is provided.

3102 - Box-mounting receptacle. These differ from type 3100 in that they have no strain relief, and are designed to bring wiring into and out of a protected chassis. The 3102 series is the most common type of chassis receptacle used on military gear.

3106 - Straight plug. This is the most common series of plug used to mate with the 3100 - 3102 series for control or power cables. These plugs can be equipped with a number of strain relief styles, including clamp, potting cups, and watertight (MS-E series only).

3108 - Same as 3106, but has a backshell that allows its wiring to exit at 90 degrees.

The next single character indicates the connector class.

A - Most common and least expensive. Solid endbell.

B - Same as Class A, but with a split endbell.

E - Rated for hostile environments, such as moisture, oils, grease, etc. Generally more expensive than A or B.

F - Replaces Class E in some types of connectors.

The next two or three characters, 14S, identify the shell size. This code does not always have a letter following it.

The remaining pair of characters, 5S, identifies the contact arrangement. If this code is followed by 'S,' it indicates female-style pins ('socket'). If it is followed by 'P,' it indicates male contacts ('plug').

For one variant on the 'Bayonet' style...

The numbers for the newer 26482 spec connectors are nearly identical to those described above. The differences are mainly in the four-digit string that identifies the connector type. Here are some examples.

3116 - Equivalent to 3106, but sized under MIL-C-26482 instead of MIL-C-5015. Straight plug, solder cup non-removable pins.

3126 - Same as 3116, but has crimp-style removable pins.

Some words about tooling...

Constructing any type of cable is an art, one that must be learned well if one is to produce a quality product. Anyone can learn how to solder well enough to get by, but if you plan on working with the crimp-style connectors, it is CRITICAL that you spend the money needed for the right tools. Using incorrect tooling can result in early failure or poor reliability of your connectors and your equipment, a proposition that could be a lot more expensive in the long term than simply spending the bucks for the right tools to begin with.

Daniels Manufacturing Company is the leading maker of crimping tools for mil-spec and commercial connectors. If you plan on doing a lot of work with the 312x series of connectors mentioned here, you should purchase one of their M22520/1-01 crimpers, along with an M22520/1-04 Positioner Assembly. This particular positioner is a universal type that will accept Size 12, 16, or 20 contacts with a spin of the barrel.

Such crimpers, although not particularly cheap, are top-quality units that will last a lifetime. I see them as an investment rather than an expense. Daniels can give you the names of any number of distributors, and I urge you to shop around as prices can vary widely.

In general, expect the tool plus a positioner to run approximately $300.

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