I know that there are probably lots of videos out there if you Google how to make your own ethernet computer cables, but I’m nevertheless going to give you my knowledge based on some thirty years experience. And I am not going to try and sell you any cable, connectors or tools, either...
1. First, let’s get our terms correct: A cable is a bundle of wires, usually coated with a colored plastic sleeve. The wires are inside the cable (See cable definition). So, when we talk about “making a cable,” we’re actually putting a connector at each end of a bundle of wires, so that the current can pass through each wire separately and continuously. Standard ethernet cables are terminated with a RJ45 connector, punch block or device. Telephone cables, which can be CAT 5, are terminated with a 66 Block, discussed elsewhere.
2. Why would you want to learn to make your own cables? First, if you’re going to need more than one, it’s far less expensive than purchasing pre-made ones. Also, you can determine the exact length you need, eliminating waste. And it’s good to have the knowledge to make one in case you don’t have any pre-made cables and you need them immediately and can’t just run to the store for them.
3. You don’t need lots of fancy tools to do this: With the exception of the “crimper” which clamps the wires into the connector, you can even make due with a sharp scissors, although a wire cutter and wire stripper can be helpful. Most of the newer crimpers (about $50) work with both telephone and ethernet cables. The photo at left shows a connector inserted into the crimper, note the built-in wire cutter. Photo on the right, you’ll notice how I’ve labeled the crimper handles to show the wires for telephone and ethernet for quick reference. (If you’re making coaxial cable (the thick TV cable), you may require a special stripper in addition to a special crimper, but the principles are the same. And remember not to cut off the woven metal mesh between the plastic and the wires, it has to be peeled back before crimping on the connector. But that’s another tutorial.)
4. Other than that, you only need the actual cable and connectors. A cable consists of the wires inside (which can vary in number between four and eight) and the connectors you use will also vary in size depending on the number of wires inside the cable. For example, telephone cables can have four wires and will fit into a RJ 11 connector for that purpose. Ethernet (computer) cables have eight wires and therefore an RJ 45 connector will have eight slots for that purpose. The cables are twisted to prevent crosstalk and interference, the more twists, the more protection (i.e. CAT 6 has more twists than CAT 5). Simple as that.
5. So let’s get going.
A. Cut a length of cable equal to the amount you think you’ll need plus about a foot extra to account for snaking behind desks or other equipment (about three feet extra if you’re pulling it through a wall). Also, to cut and re-do if you don’t do it right the first time. It’s always better to have more cable than less, of course.Make sure each end is cut neatly and evenly, it’ll make your job easier.
B. Next, with a scissors or cutter, cut at least an inch off of the plastic sheathing of the cable. You can use a sharp scissors and rotate the wire or the scissors to cut just the plastic. You don’t want to cut into the wires inside, which are very thin and can be easily nicked. Even a slight nick will degrade the signal substantially, slowing down your connection, or cause it to break off, severing the connection completely. Therefore, you may want to practice this a couple of times first. Then pull off the plastic outer sheathing you’ve cut, revealing the wires.
C. You’ll notice a bundle of wires and a string. The string is for you to pull if you want to strip even more plastic off of the cable. You can clip the string off if you don’t need it. What’s left will be a group of wires of varying colors, some solid, some striped. They are twisted to prevent cross-talk or interference. If so, untwist them slightly and pull them flat.
D. The arrangement of the wires is crucial. They must be in a precise order. Flatten out the wires so that they lay alongside each other. Then, arrange them side-by-side by the proper colors. Click HERE to see the color codes for telephone and ethernet cables. Ethernet (CAT 5) is shown on left, while phone (CAT 3) is red-green-blue-yellow, RG line 1 and BY line 2, or on ethernet cable, Blue, Orange, Green, Brown, Slate. When you’re done, flatten them out again, then cut them to an even length of about one half inch. Never strip the wires, as they won’t work with the connector. This isn’t electrical wiring - the connector will do the work when it is crimped.
E. Put the connector into the crimper. Most crimpers work with the “clip” of the plastic connector facing down. (See 3, above)
F. Still holding them flat, feed the wires into the connector, pushing them slightly, until you feel them hit the end of the connector. At that point, you should see about 1/8” of the plastic cover of the cable also fit inside of the plastic connector. If it doesn’t, pull the cable out and trim the wires straight across until it does. (It’s important that the cable fit slightly inside the connector because that’s what makes it hold the cable tightly.) Make sure that the wires are fitting flat inside the connector, that they haven’t become crossed or are sitting on top of each other. When you’re sure, firmly squeeze the crimper as far as it will go. Do it one extra time to be sure. Then take the cable and the connector out of the tool. Pull it to make sure it’s tight. But if it comes off, do it again, correctly. This sometimes takes a little practice.
G. Do the same thing with the other end of the cable. Make sure both times, you have inserted the wire into the clip the same way, with the clip facing down. You don’t want to reverse the colors. If you do, the cable won’t work.
H. Try the cable with your equipment and see if it works. Those of us who do this professionally have cable testers (starting at about $50) which test the “continuity” of each wire, so we can isolate any wire pairs which do not pass the signal from one connector to the other, but since only 4 of the wires (i.e. Pins 1,2,3 & 6) are necessary to permit the cable to function properly for basic computer purposes, at least with ethernet cables you have some wiggle room.
I. Don’t expect this to work perfectly the first time. It took a little trial-and-error for all of us to get the right feel. And if you don’t do it every day, you may lose your touch a little.
J. In my opinion self-made cables are never as good a pre-made cables. The manufactured cables are tighter, have “boots” holding them on, preventing flexing at the end of the connector that can loosen the wires, are pre-tested for continuity, and may even be molded right into the plastic. They will last longer and perform better no matter how good you may become at making your own cables. Particularly for certain functions, like patch panels, where you are going to be pulling them out time and again, you’re better off using a manufactured cable. Sure, you can make a cable to test the system, but when you’re done, you should replace it with something stronger.
Of course, these are just the basics. There are many different types of even ethernet cables (e.g. CAT 5, 6, plenum, teflon) and connectors (some better than others, some made to fit specific types of cables), but the principles remain the same.