How to Use Wire Strippers Properly

Using wire strippers comes down to three things: pick the hole or setting that matches the conductor size, close the jaws just enough to cut the insulation and not the metal, then pull the offcut straight off the end. Get the size wrong and you either leave the insulation attached or shave metal off the conductor, which weakens the connection long before anyone notices. This guide covers the main stripper types, the technique for each, and how to tell a clean strip from a bad one.

Know which type you are holding

Most of the confusion around stripping wire comes from people applying the technique for one tool to a completely different one. There are four common designs and they behave differently.

• Gauged manual strippers. The classic plier-shaped tool with a row of labelled holes. You choose the hole, squeeze, twist slightly, pull.
• Self-adjusting strippers. One jaw grips the wire while the other clamps and pulls the insulation off in a single squeeze. No sizing decision at all for common conductor sizes.
• Adjustable-stop strippers. A single blade with a thumbscrew or dial that limits how deep it bites. You set the depth once for the cable you are working with.
• Combination strippers. Cutters, crimp jaws and a few stripping notches on one tool. Convenient, usually the least precise of the four.

If you mostly work with UK twin and earth or flexible appliance cable, a self-adjusting pair handles the bulk of it. If you deal with a wide spread of sizes including very fine wire, gauged strippers give you more control.

Work out the conductor size first

Strippers are sized by the conductor, not the outer diameter of the insulated wire. UK cable is marked in square millimetres, so 1.0mm², 1.5mm² and 2.5mm² are what you will meet most often around the house. Imported tools and a lot of automotive wiring use AWG instead, where the number gets smaller as the wire gets thicker. As a rough pairing, 1.0mm² sits near 18 AWG, 1.5mm² near 16 AWG and 2.5mm² near 14 AWG.

If the cable sheath is unmarked or worn off, sacrifice a short offcut and test the size before you strip the piece that matters. Better to lose 30mm of scrap than to nick the conductor on the run you have already pulled through a wall.

Stripping with gauged manual strippers

1. Decide how much bare conductor you need. Screw terminals usually want 8mm to 12mm; a plug top or connector block may want more. Terminals should cover the bare metal completely once the wire is in.
2. Lay the wire into the hole marked for its size, with the end of the wire sticking past the jaws by the length you want to remove.
3. Squeeze until the handles stop. Do not force past the natural stop point, that is what puts a bite mark in the copper.
4. Rotate the tool a quarter turn around the wire to score the insulation all the way round.
5. Pull the tool straight off the end. If the insulation resists, you are in a hole that is one size too big.

The wire should come out with a clean square shoulder of insulation and no scratches on the metal.

Stripping with self-adjusting strippers

These need less decision making but more attention to the length stop. Push the wire in until it hits the adjustable stop at the side of the tool, then squeeze the handles fully in one movement. The jaws grip and separate at the same time, and the insulation slug comes away as you release.

Two things go wrong with self-adjusters. First, very thin wire under about 0.5mm² can slip in the grip jaw and stretch instead of stripping. Second, tough insulation on older or heat-resistant cable sometimes needs a second squeeze rather than one hard one. If the tool keeps stretching the conductor, switch to a gauged pair for that job.

Handling stranded versus solid conductors

Solid conductors are forgiving to insert but unforgiving to nick. A single ring cut around a solid wire creates a stress point, and if that wire is flexed during installation it can snap inside the terminal where nobody will ever see it.

Stranded wire spreads the risk, but you can shear off individual strands without realising. Losing three or four strands from a 1.5mm² flex measurably reduces its current capacity and leaves a connection that runs warmer than it should. After stripping stranded wire, give the strands a gentle twist in the direction they were already laid so they stay together, and count that none have been left behind in the insulation slug.

Do not solder the ends of stranded wire before putting them into a screw terminal. Solder creeps under pressure, so the joint loosens over time.

Getting the outer sheath off flat cable

Stripping the grey outer sheath from twin and earth is a separate job from stripping the individual cores, and wire strippers are the wrong tool for it. The usual method is to find the bare earth conductor running down the middle, grip it with pliers and pull it back along the cable so it splits the sheath from the inside. Then fold back the flaps of sheath and trim them off with side cutters or a knife drawn away from the conductors.

If you do use a knife, cut along the flat face rather than the edge, and only score deep enough to break the surface. A knife dragged around the circumference of a cable is how insulation on the cores underneath gets cut.

Checking the strip before you connect

Look down the length of the bare conductor under decent light. You are checking for bright scratch lines, flat spots, or a visible step where the diameter has been reduced. On stranded wire, count for missing or splayed strands. Any of those means strip it again a few millimetres further along rather than hoping it holds.

Then check the length. Bare metal visible outside a terminal is a real hazard, and conductor buried so deep that insulation is clamped under the screw is a connection that will loosen and heat up. Aim for the metal to fill the terminal with the insulation stopping just at the entry.

Keeping the tool cutting cleanly

Wire strippers dull faster than people expect, mostly from being used as makeshift cutters on things they were never meant for. Keep them out of screws, nails and cable ties. Wipe the jaws after use, put a drop of light oil on the pivot occasionally, and store them where the jaws are not being knocked against other tools.

When a stripper starts tearing insulation instead of slicing it, or you find yourself squeezing harder every time, replace it. A worn pair costs you far more in damaged conductors and remade connections than a new one costs to buy.