Stripping Insulation Without Nicking the Copper

A wire stripper has a row of holes, each sized for one gauge. Put the wire in the hole with its own number on it, squeeze, and the blades close to exactly the conductor's diameter — cutting the insulation and stopping at the copper. Using a hole one size too small cuts into the conductor. One size too large and the insulation tears instead of cutting, and you drag it off, stretching the wire behind it. Both are visible under a loupe and neither is visible to the naked eye. If the gauge is unmarked or unknown, start with a hole that is definitely too large and work down until the insulation parts cleanly. That costs three seconds and one scrap end.

A blade pressed hard enough to cut PVC is pressed hard enough to score copper, and the score is exactly where the wire will break. The common workaround — rolling the wire under the blade to cut all round — produces a ring of small nicks instead of one, and a ring of nicks is a perfect fracture line. It is worse than a single cut, not better. Where there is genuinely no stripper, the least bad method is to soften and pull: grip the insulation with pliers and draw it off, or for thick cable make a LENGTHWAYS slit well back from the end and fold the insulation open rather than cutting around the conductor. A lengthways cut does not create a break line.

Too little and the conductor does not reach the bottom of the terminal; too much and bare copper stands proud of it, ready to touch its neighbour. The right length is set by the joint, not by habit. For a screw terminal, just enough that no bare wire shows outside the clamp. For a crimp, exactly the length of the barrel. For a solder joint on a pin, enough to wrap or sit against it and no more. Offer the stripped end up to the terminal before committing. A wire stripped too long can be trimmed; one stripped too short has to be cut back and redone, which shortens the wire every time and eventually costs you the whole run.

Give stranded wire a light twist in the direction its strands already lie, just enough to keep them together. Heavy twisting distorts the bundle and makes it harder to seat. Do NOT tin a stranded wire that is going into a SCREW terminal. Solder creeps under sustained pressure — it flows slowly away from the clamped point — so the screw gradually loosens over months and the joint heats up. This is a real documented failure mode and it is forbidden in professional practice for exactly that reason. The correct answer for stranded wire into a screw terminal is a bootlace ferrule: a metal sleeve crimped onto the strands that presents a solid, non-creeping end to the screw. Tinning is fine where the joint is soldered anyway, and wrong wherever a screw is doing the clamping.