I recently purchased some of these: Digi-Key Banana Jack. Unfortunately, I'm new and there isn't the supporting documentation I need to be able to determine how they're to be used.

Side view Bottom view Top view

Unlike other banana jacks, there is not a hole to feed the wire through and screw down on. I understand the large nut is for holding it against the enclosure, but I don't know what the intention is with the threaded bottom section and the two nuts. I'm guessing that the wire is simply looped around and a nut is tightened down against it, but this doesn't seem very durable. Why the double nuts, what is supposed to be done with them?

Edit To clarify, I understand that they are the female piece of a banana connector. I have male banana connectors that I am using these with. My lack of understanding comes from how to wire this female piece to the... for lack of a better word "connection wire". I.e. how to wire this female portion into a circuit so that the circuit is accessible through it.

  • \$\begingroup\$ That's not a binding post. Its a banana-jack and is only intended to have a banana-plug inserted, not to accept bare wires. The nuts at the bottom are for holding a ring-lug. \$\endgroup\$
    – brhans
    Commented May 20, 2015 at 18:19
  • \$\begingroup\$ Use a ring lug, preferably a star ring lug, or use a regular ring lug + lock washer, as in my answer below. \$\endgroup\$ Commented May 20, 2015 at 18:43
  • \$\begingroup\$ @brhans Ah... I now see that while trying to figure look this up myself I totally misunderstood. Banana jacks seem to commonly be used in similar situations to binding posts, and the terminology seems just inconsistent enough to confuse me. Thank you for clarifying! \$\endgroup\$ Commented May 20, 2015 at 18:45

3 Answers 3


Run down to your local hardware store and get matching ring crimp terminals and non-slip washers. Crimp the terminals onto wires, then slip them in between the nuts on the bottom with a non-slip. This will provide a fairly secure connection, dependent on how well you crimped the terminal of course.


As the data says it mates with a "standard banana". Standard is 4mm.

Something like this:

enter image description here

Or this:

enter image description here

Not this (but perhaps you can see the resemblance in the springy bits):

enter image description here

The part you have (female) is just a hollow tube with no springy parts, so it depends on the male to supply the compliance. Some plugs have a cross-drilled hole so another banana plug can be inserted sideways.

The screw and nuts are to fasten onto a ring terminal or onto a through-hole PCB. In the case of the PCB, a toothed lockwasher is a good idea. In the case of the terminal, a toothed "star" terminal can be used (photo from here).


You drill a hole as the datasheet shows and attach the jack to a panel with the large nut.

enter image description here

The datasheet indicates that the jack also accepts shrouded plugs (insulated on the outside of the metal and often with plastic at the end so that a human finger cannot contact the metal). This is commonly used on the meter end of test leads.

  • \$\begingroup\$ I'd upvote you for breadth of the answer, but I don't have enough reputation as it stands. I appreciate the effort, although you seemed to misunderstand my difficulties to begin with. Thanks for the clarification! \$\endgroup\$ Commented May 20, 2015 at 18:51

The threaded post on the back is intended for a ring lug. The diameter of the ring can be 4mm or US screw #8. To make a better electrical contact, add a star washer between the nut and the rung lug.

enter image description here Source: Datasheet for the banana jack.

crimp-on ring lug ring lug and star washer

US screw sizes, Metric screw sizes

p.s. Pomona is a reputable supplier. I would expect a better drawing from them. The datasheet claims "IEC" and "4mm". Yet, the dimensions are only in inches, including dimensions of metric threads.


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