Before a wire can be crimped to a terminal or soldered to a connector, its protective insulation must be removed. This process seems incredibly simple, yet the critical importance of proper wire stripping techniques is often underestimated. In professional wire harness manufacturing, a bad strip is an automatic quality control failure.
Stripping a wire is not just about removing plastic; it is about doing so without inflicting any microscopic damage to the fragile copper conductor beneath.
The Anatomy of a Perfect Strip
A perfectly stripped wire has two defining characteristics:
- Zero Conductor Damage: Not a single copper strand has been cut, nicked, scraped, or deformed by the stripping tool.
- Clean Insulation Cut: The edge of the remaining insulation is cut perfectly square (90 degrees), with no jagged tears, stretching, or melted edges.
The Dangers of a Bad Strip
When technicians use dull tools, incorrect gauge settings, or rush the process, they create “nicked” strands. This happens when the stripping blade cuts slightly too deep, slicing through the outer layer of copper strands along with the insulation.
Why is this catastrophic?
- Reduced Current Capacity: If you are working with a 14 AWG stranded wire, and you accidentally cut off 15% of the strands while stripping, that wire is no longer a 14 AWG wire. It has been downgraded. If the circuit demands the full 14 AWG capacity, the narrowed “bottleneck” at the strip point will overheat and potentially catch fire.
- Mechanical Weakness: A nicked strand is a stress riser. Under the constant vibration of a running engine, the nicked strand will quickly fatigue and snap completely, causing the connection to fail prematurely.
How-To: Professional Wire Stripping
To guarantee a perfect strip every time, follow these industry best practices:
- Use the Right Tool: Throw away the cheap “multi-tool” wire strippers found in bargain bins. Invest in a dedicated, high-quality automatic wire stripper or precision machined manual strippers designed specifically for the exact wire gauge you are using.
- Calibrate the Depth: If your tool is adjustable, calibrate it on a scrap piece of wire first. The blades should score the insulation deeply enough that it tears away easily, but the blades must never actually touch the copper.
- Don’t Twist the Strands: After stripping, resist the urge to tightly twist the bare copper strands with your fingers. While this makes it easier to push into a hole, the oils and acids from your skin will rapidly accelerate copper oxidation (corrosion) inside the final crimp. Handle bare copper as little as possible.
- Related reading: Learn more about wire gauge
Improper wire stripping is one of the most common, and most preventable, causes of harness field failures. Stripping too deep can nick individual conductor strands, creating a weak point that may not fail immediately but will fatigue and break under vibration over time. Stripping too shallow leaves residual insulation between the conductor and the terminal, increasing contact resistance and creating a poor crimp. Precision wire strippers with gauge-specific blade settings, rather than adjustable manual strippers, are the standard for production environments where consistent strip length and depth need to be maintained across thousands of terminations.
For related reading, see our article on the definitive guide to proper wire crimping techniques. You can also learn more about our quality control process. These practices are consistent with standards such as ISO 9001.
Clean, consistent stripping is non-negotiable at the fine-pitch scale of our Fine-Pitch FFC/FPC & Board-to-Board Cable Assemblies.
Frequently Asked Questions
In high-end aerospace applications (like Teflon/PTFE insulated wire), mechanical blades are often banned because the risk of nicking a strand is too high. Instead, they use thermal strippers – glowing hot electrical tweezers that melt the insulation off without any sharp metal ever touching the copper.
This is entirely dictated by the terminal you are attaching to. You must strip exactly enough wire so that the bare copper fills the entire crimp barrel, but not so much that bare wire is left exposed outside the back of the terminal.
Absolutely not. It is impossible to consistently control the depth of a knife blade by hand. You are virtually guaranteed to score or nick the underlying copper strands.
