What are Jam Nut Connectors?

By Amy Goetzman | January 23, 2024

Meet the Connector: Jam Nut Connectors

Jam nut connectors feature a jam nut (hex nut) that screws onto a circular connector’s threads to mount it and secure the electrical connection. Jam nut connectors are used to save space in crowded panels, walls, or boxes. They also improve stability, making them an ideal choice for applications in high-vibration environments such as aeronautics, military equipment, telecom installations, and industrial panels.

A jam nut connector is inserted into the back of the panel and the jam nut is screwed onto the front, preventing the connector from falling through the hole and getting lost behind a panel. The jam nut receptacle is round with one flat side to prevents the connector from spinning. The use of a jam nut can often be accomplished with hand-tightening (without tools or screws), making installation fast, easy, and secure.

This type of connection originates in mid-1900s military and aerospace electronics and is commonly used in crowded instrument panels for aircraft, spacecraft, and military ground vehicles where electronic connections to instrument displays are behind the screen.

Although it is a legacy connector format, suppliers continue to refine their jam nut offerings to meet modern requirements, such as reducing SWaP. The format has also been introduced to newer interconnects, such as RF and coax products.

Amphenol Aerospace offers a selection of reduced flange jam nut connectors

Amphenol Aerospace offers a selection of reduced flange jam nut connectors to minimize the footprint needed inside the box or on the panel.

Design Notes

Standardization

Jam nut mechanisms are used in many standardized circular products, including MIL-spec products such as the D-38999 and RF products such as SMA, LC, ST, SC, and MTO/MTP connectors.

Mounting type

Panel mount

Materials specifications

Jam nut receptacles are made in plastic and metal materials, in a variety of shell styles and insert configurations.

Molex’s SMA Jack RF connector includes a jam nut

Molex’s SMA Jack RF connector includes a jam nut and lock washer for additional stability.

Physical properties

In a dual-locking format, the primary nut is tightened around the connector, and the secondary one is tightened against it to create a robust and secure connection.

In applications that are exposed to environmental stress, a sealing ring or coating may be included.

Environmental properties

Jam nut connectors can be well sealed and are good choices for hermetic applications. An integrated O-ring seal provides a secure sealing mechanism, and the bulkhead type attachment reduces potential points of ingress.

Electrical properties

Voltage AC/DC

Current rating 7.5 Amps

Markets and Applications

Industrial, Military and Aerospace, Telecom/Datacom, and others.

Suppliers

Jam nut connectors are available from many suppliers, including Amphenol Aerospace, Glenair, ITT Cannon, Molex, TE Connectivity, and others.

Related products

  • D-38999
  • Circular connectors
  • RF connectors
  • Rack and Panel
  • SMA
  • MTO/MPO

Like this article? Check out our other Meet the Connector and Circular Connectors, our Mil/Aero Market Page, and our 2023 Article Archive

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Amy Goetzman
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