Plastic coated NM, or non-metallic, electric cable comes with three layers of protection that need to be removed before you can get to the actual copper wire: first, an outer plastic casing, then paper, then another layer of plastic on the wires. The first action you perform is cutting off that tube-like outer layer of plastic casing. As with cutting lumber lengthwise, this action is called ripping.
Learning how to effectively rip plastic casing is essential to doing electrical work. When wiring outlets, lights, or any other home electrical system, you will find yourself ripping cable casing numerous times. If you can learn to do this without much thought, it becomes second nature and your project goes faster.
Wire Ripping vs. Stripping
On Romex brand and other NM cable, casing is the heavy plastic sheathing that binds two or more individual wires. Each of these copper wires is coated with a thin layer of plastic.
When you remove this outer casing or sheathing, this ripping action is performed by using a cable ripper. When you remove the colored casing from the inner wires, this action is called stripping. For this, you use a different device called a wire stripper.
Electric Cable Ripper Basics
When you have several wires within the Romex-style plastic cable casing, you often need to loosen and separate those individual wires to attach them to terminals of an electric outlet, switch, circuit breaker, or other device.
You can laboriously slice the casing away with a knife, but you risk cutting into the copper wires' own casings.
The cable ripper is the only way to do this safely and quickly. The ripper is a helpful, though not foolproof, way of slicing away casing without damaging the inner wires' coating.
The cable ripper is simply a U-shaped, stamped-metal tool with a tiny cutting head within it.
When you pull the cable ripper down the length of the cable, the cutting head penetrates the outer cable but leaves the inner wires untouched. The cutting head is barely sharp enough to prick your finger, yet with pressure, it will rip cable casing.
How to Use a Cable Ripper
The cable ripper is an imperfect tool and requires a sure hand. Poorly ripping cable can have dire consequences. If you rip too deeply, you risk cutting into the wire casing. This can be a safety hazard, as the copper needs to be covered to prevent shorts and arcs. Another consequence is that if you have wires that do not extend very far from an electrical box and you rip too deeply, you effectively shorten your wires by another few inches. With wires that are already too short, this is wire that you cannot afford to lose.
- Position: Hold the cable ripper with the V-shaped end facing away from your body.
- Placement: Insert the cable into the hole in the cable ripper. Push the ripper upward until you reach the point where you want the rip to begin. It may be helpful to first make a mark on the casing with a Sharpie so that you know where to begin the rip. This ensures that you do not rip too far up.
- Pull: Exert light pressure on the two sides of the cable ripper until the cutting heads touch the casing. Rip in the direction of your body quickly and lightly, ensuring that you do not nick the inner wires. If you slice too hard, you risk slicing off the casing of the inner copper wires. It is best to avoid this. Instead of a single hard rip, try running your cable ripper very lightly several times down the cable. The goal is not to slice in one stroke, but to create a perforation that allows you to rip the casing off by hand. It may take as many as three strokes to do it this way.
- Separate: Often, the ripped cable is not entirely cut. Instead, it is perforated. Put down the cable ripper and pull the casing away from the inner wires until you can go no further. Snip off the rest of the casing and the paper with scissors or a utility knife.