2 Replies Latest reply on May 20, 2019 2:42 PM by three-phase

    Crimpers for SMA Connectors


      Hello all,


      I have been using up some old components as part of a project recently that involved making connection leads using RG174 coax cable and some SMA plugs. I struggled to solder on the centre pin, as it melted the inner insulation and then the body of the SMA connector would not go over it.


      The SMA connector I am using is; https://uk.farnell.com/multicomp/mc23554/rf-coaxial-sma-straight-plug-50ohm/dp/2112461?ost=2112461&ddkey=https%3Aen-GB%2…


      The instructions for the SMA connector detail that the centre pin of the SMA plug requires a 0.024 square crimp.


      SMA Connector instructions


      My crimp set has a die that only goes down to 0.042. I have looked around my usual suppliers in UK, Farnell, RS Components, Digikey and Mouser and none seem to have a die with a 0.024 square crimp.


      My coax crimp set


      0.042 die set


      I was wondering if anybody could advise of a crimp die that would be suitable for this SMA connector?


      Many thanks.

        • Re: Crimpers for SMA Connectors

          Hi Donald,


          I've checked, both the coax crimpers I have (one is in the style you have, and the other is a Pressmaster removable die), and the small setting is 0.028 (0.7mm) and is square die, and neither tool is more than 0.1mm accurate I feel, so should work.

          The crimper in the same style as yours is called HT-336T, but appears not available any more from Farnell : (

          The Pressmaster one is die code 4300-3140/AAA4300-3140/AAA and the empty tool code is 4300-3149/AAA4300-3149/AAA .

          However, having said that, I've never crimped the centre pin of RG174, always soldered (I didn't even know that center contact could be crimped, as you say the datasheet does seem to specify that). As an example, I've used this RG174 SMA plug RG174 SMA plug in the past, and it's datasheet specifies to solder the centre contact.

          To do that, there is a hole intended for very thin solder, and then afterwards the outside needs excess solder trimmed off with a sharp knife/scalpel. I sometimes use a different method, push some solder paste into the hole and around the centre conductor, then push it in, and just heat with iron from outside (and then trim with knife, or first try to add a bit more solder from the side - that ideally needs extremely thin solder though, < 0.3mm). Then I use the crimp tool just for the outer ferrule. Both tools are 'average' (can't say I'm totally happy with either one, but they do function. If you've only got a few of these connectors to use up, I reckon it may be easier to solder the pin and it will work electrically really well (knowing your neat work/attention to detail!) at those RF frequencies. Also I'm sure you are already aware, if you've got adhesive heat-shrink that is nice around the ferrule, or even normal heatshrink, but I guess not essential.

          (EDIT - sorry just saw that you mentioned you did try soldering.. usually I'll use RG-316, which is almost identical size, and compatible with the plug I think, and is PTFE. With RG-174, perhaps the results won't be perfect soldering, but I still think you'll achieve good results even with the slight damage to the dielectric for the millimetre or so.

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            • Re: Crimpers for SMA Connectors

              Many thanks shabaz. Spot on with the help again.


              The HT-336T dies set appear to be available in America but not UK, so I will go for the Pressmaster crimper. Soldering the centre contact onto the cable goes ok, but the slightest bit of heat causes the centre insulation to shrink back and bulge up. It is then too large to be inserted into the plug body, as it is already a tight fit.


              I did try trimming off the insulation to get it to fit but it didn't cut very easily with the knife, and I was just making a big mess of the outer braid. I have already wasted two plugs trying the solder approach and I am not keen to keep trying, given the cost of them.


              On this particular project they are not being used at RF frequencies, I am just using them up, as they have been sat around for some time now as extras that were purchased when I was installing a 2.4gHz wireless camera controller to monitor a peregrine falcon's nest.


              Kind regards.

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