Can anyone identify this coax connector? I think it might be an SMA female connector but I'm no expert. It has threads on the outside and a hole inside. The diameter (to the outside of the threads) is 5.25 mm. The pink ruler in the first picture is in cm. The yellow tape measure in the second picture is in inches.

The connector is on a shaker that I need to connect to an amplifier. The cable that connects them is missing, so I'm going to get a custom one. The other end of the cable will have a dual banana plug. Is there a particular type of cable I should use in this application?

UPDATE: it's not SMA. Or SMB, for that matter; I took it to a hardware store yesterday and tried both. They didn't have any SSMA or SMC for me to try, though, so I suppose it could be one of those...

Coax connector in mm enter image description here

  • \$\begingroup\$ Might want to take a better photo that shows the thread and internal pin more clearly. Higher resolution wouldn't hurt, either. It's kinda hard to see from the photo you posted. \$\endgroup\$ – Polynomial Sep 3 '13 at 16:21
  • \$\begingroup\$ I've added a better picture, I hope that helps. And there is no pin inside, by the way. \$\endgroup\$ – user28432 Sep 3 '13 at 16:51
  • \$\begingroup\$ It won't be an SMA unless your measurement is quite a bit off, to the outside threads of an SMA female should be 6.24mm and as a double-check I just measured one as 6.29mm using calipers. \$\endgroup\$ – PeterJ Sep 4 '13 at 6:44
  • \$\begingroup\$ Update: you're right, it's not SMA. Or SMB, for that matter; I took it to a hardware store yesterday and tried both. They didn't have any SSMA or SMC for me to try, though, so I suppose it could be one of those... \$\endgroup\$ – user28432 Sep 5 '13 at 15:15


The SMA female would generally fit the description and is commonly used in these types of applications.


The threading (I don't really see it in the photos), if present, looks either way too fine or way too coarse. The barrel also looks too short to be SMA, but again that's just the photo?

To test...

Get a 0.312" (5/16") outer-diameter (lands spacing) hex nut with 1/4" 36TPI threading from your local hardware store.

enter image description here This is the Tyco Electronics 2-332004-0: 5/16" 1/4-36 Steel Hex Nut

If you don't have good hardware stores (like we have in Silicon Valley), you can order one from Digikey or other online vendors.

If it threads on (don't force it!) then you are almost certainly dealing with an SMA given your other connector properties.

Good luck with your project.

  • \$\begingroup\$ Incorrect. The threads on an SMA are 1/4-36 which is not a hardware store size. The wrench nut is 5/16" across the flats but not the threads, so a 5/16 nut will not fit, and neither will a 1/4-20 nor a 1/4-28. \$\endgroup\$ – Chris Stratton Sep 4 '13 at 1:54
  • \$\begingroup\$ There is nothing incorrect about what I wrote. I did however omit the threading. That has been corrected. Thank you for the report. \$\endgroup\$ – DrFriedParts Sep 4 '13 at 3:14
  • \$\begingroup\$ I've also added a reference to a nut to show that you can buy them as described. \$\endgroup\$ – DrFriedParts Sep 4 '13 at 3:20
  • 1
    \$\begingroup\$ @DrFriedParts For a moment I interpreted "you can order one from Digikey" as ordering a good hardware store. :-) \$\endgroup\$ – Anindo Ghosh Sep 4 '13 at 3:27
  • 1
    \$\begingroup\$ You need a 1/4-36 nut. The OD is irrelevant to the application. When only one dimension is given as you had, that is the thread major diameter size - the item your post now pictures is not a "5/16" nut, and your mistake was in calling it such. Calling out only the size across flats instead of the thread major diameter gives no helpful information for the fit and only misleads those who assume you would be conforming to standards. A "5/16 nut" will not fit, a 1/4-36 will. \$\endgroup\$ – Chris Stratton Sep 4 '13 at 5:39

protected by Kortuk Sep 4 '13 at 0:29

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