On Romex(R) brand and other NM (non-metallic cased) wires, casing refers to the heavy plastic sheathing that binds two or more individual wires. Each of these wires are coated in a thin layer of plastic.
When you remove this outer sheathing (casing), this action is ripping. For this, you use a cable ripper.
When you remove the casing from inner wires, this action is stripping. For this, you use a wire stripper.
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, etc.
You can laboriously slice the casing away with a jackknife, but you risk cutting into the copper wires' own casings.
Bad news there: short circuits and fires can result. Enter the cable ripper. The ripper is a helpful, though not 100% foolproof, way of slicing away casing without affecting inner wires' coating.
The cable ripper is simply a U-shaped, stamped-metal tool with a tiny cutting "head" within it. It is just about the lowest, low-tech tool imaginable.
When you pull the wire 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 It
The cable ripper is an imperfect tool and requires a sure hand. Learn these skills to effectively use one.
- Position: Hold the cable ripper with the "V"-shaped end facing away from your body.
- Placement: Insert cable into the hole in the cable ripper. Push the ripper upward until you reach the point where you want the rip to begin.
- Pull: Put light pressure on the two sides of the cable ripper until the cutting heads touch the casing. Rip in the direction of your body lightly, ensuring that you do not nick the inner wires.
- 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.
Cable Not Ripping? Try This Trick
Seasoned electricians don't have to do this. But "seasoned" I am not. It's just a quick tip for slicing off the thick plastic casing from electrical wire.
The problem: slice too hard, and you risk slicing off the casing of the inner copper wires. While not exactly the end of the world, it's better to avoid this.
Instead, run your cable slicer very lightly several times down the cable. The goal is not to slice in one stroke, but almost to create a perforation that you allows you to rip the casing off by hand.
For me, it usually takes three strokes.