CTA Tutorial: Crimping BNC Connectors

I’ve written a whole series on soldering XLRs, 1/4” plugs and Speakon connectors, but I’ve never done a post on BNCs. A few months back, while I was wiring our video rack, I decided to take some pictures of the process. Several people asked if I could write this up, along with a list of tools and connectors I use. I’m happy to do so, but with a simple caveat; I use what I use because it works for me, and I’ve had good luck with the tools, connectors and cable. There are other varieties of all available, so this is not a “you must do it this way” post. I’m showing you my process, with my stuff. Feel free to copy it though, it works great.

This is my BNC connecting kit. We have multiple strippers calibrated for different wire types. 

This is my BNC connecting kit. We have multiple strippers calibrated for different wire types. 

Parts is Parts

First, we’ll start with the tools and parts list. Terminating coax is actually pretty simple, and once you get things in place, you can do an end in under a minute. Here’s what I use. 

Cable: Gepco VPM-2000

Connectors: Kings 2065-2-9

Cable Stripper: Paladin CST Vario 3 blade adjustable stripper

Crimper: Paladin 1389 full-ratchet crimper

In the past, I’ve used Beldin cable, as well as Canare, and I find the Gepco easier to manage. The braiding is much easier to flare out without tearing it all up. It’s also affordable and stocked 40 miles from me. Kings has been my BNC of choice for over 15 years. I’ve simply never had one fail. Note that I’m using the 2065 series, which is their 75 Ohm connectors (which you should use if you plan to do HD ever). 

The “2-9” destination indicates the variant for that particular cable. Most of the problems people have with terminating BNCs stems from not using the correct connector for the cable. Not all cables are the same diameter, so the center pin won’t crimp fully, or the outer crimp will be weak. If you choose to use Kings, you can find their connector/cable reference here. Most cable manufacturers also have a cross-reference. If you properly match the cable to connector, you won’t have any problems. 

We went through several strippers before I found one I really like. The CST Vario is about $90 at Markertek, it’s totally worth it. You can get the blades adjusted exactly right for your connectors (look up the instructions for assembly, they’ll tell you what the strip lengths should be), and I’ve not broken a single Vario blade. I have however, gone through about $90 worth of blade cartridges for their cheaper stripper. Spend the money the first time. 

I’m not going to get into the process for adjusting the stripper. Follow the directions with the stripper and the connectors. It will take a while to get the blades set to the right depth. Be patient, and be prepared to waste a few feet of cable. Once you get it right, you shouldn’t be nicking the center connector, and the braiding should be cut cleanly. Take the time to get this right. After it’s done, everything goes a lot easier. Trust me…

The Process

The first step is to strip the cable end. With the Vario, I will line the end of the cable up with the outside of the cartridge, and engage the rollers. I like to push the rollers up until they engage the cable, go another two clicks, then make a turn or two. After two turns, I’ll push the rollers all the way in to fully seat the blades and make 4 more rotations. After that, grip the side of the stripper and pull it straight off the cable end. If you have it adjusted correctly, it will look like this:

Don't worry about the slight bend of the center conductor, the pin will straighten it out.

Don't worry about the slight bend of the center conductor, the pin will straighten it out.

The next step is to crimp the center pin in place. I found with my 1389, I can close it 5 clicks then drop the pin into the .041 hole. I then slip that over the center conductor on the cable. A final few clicks on the crimper, and we’re done. Make sure you don’t twist the crimper when you put it on. Keep the center conductor straight. It should look like this (and not pull off under moderate tugging):

bnc-term-2.jpg

You’ll notice I’ve already put the outer sleeve on the cable (along with a heat shrunk label). I like to put the sleeve on before I start crimping so I don’t have to take the end off and put the sleeve on after I’ve adjusted it. Flare the braiding out a little bit, or if you’re using Kings, just gently slide the end over the cable. They thoughtfully put a little ramp on the connector that flares VPM-2000 pretty nicely. You should feel the center pin snap into place (it’s pretty subtle, but it does seat if your strip lengths are correct). It should look like this:

bnc-term-3.jpg

Now slide the sleeve up in place, making sure you don’t push the end off. This takes a little practice to get the feel, but it’s not hard. You should now have this:

bnc-term-4.jpg

Finally, put the sleeve (and everything else) into the right slot on the crimper (for a 2065-2-9, it’s a .255). Making sure to not jostle the connector off the end of the cable, gently crimp down. When crimping, you don’t have to squeeze extra-hard or anything; just complete the ratchet cycle. After you’re done, it will look like this (you will probably have to make an extra pass at it to finish the rest of the sleeve):

bnc-term-5.jpg

Now give it a little tug. It shouldn’t pull off even if you pull pretty firmly. If it slides off too easily, you are either using the wrong connectors for the cable, your crimper is not adjusted properly or you pulled the connector off while you were crimping. No big deal, cut the end off, re-strip and do it again.

It’s Not Hard

You can make these cables. And once you get the hang of it, wiring a video rack is easy, fun and makes the rack look really nice. The best piece of advice I can give is do your homework and get the right parts. All the manufacturers publish specs on which ends to use with which cable, and what crimp die sizes to use. Sometimes you need to dig a little bit, but you can figure it out. Don’t skimp on the tools, and they will last you a long time. Happy crimping!

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