A good electrical connection is the foundation for the safety of any vehicle. In conditions of constant vibration, temperature changes and humidity, it is the point of contact of the wire that often becomes the weak link in the chain. The use of twisting or soldering in the engine compartment is not always justified, since these methods may not withstand dynamic loads. This is where specialized wire crimping tool, allowing you to create a monolithic connection.
The crimping process ensures reliable contact by compressing the metal of the ferrule and the cable core under high pressure. This eliminates oxidation and heating that often occurs with a poor connection. For an auto electrician, having the right tool is not just a whim, but a strict necessity. Let's figure out what types of equipment exist and how to choose the optimal solution for a garage workshop or professional service.
Operating principles and the importance of the right tool
The main task of high-quality crimping is to create tight contact between the surface of the core and the inner wall of the tip. At the same time, it is important not to damage the metal structure itself, avoiding its rupture or critical thinning of the walls of the sleeve. Cheap pliers or wire cutters often deform the tip unevenly, leaving gaps where moisture can subsequently penetrate. Professional crimping tool It works on the principle of a matrix, which compresses the part from several sides at the same time.
In automotive electrical applications, where currents can be significant and space is limited, contact reliability is critical. Poor crimping leads to a voltage drop and local heating, which in the worst case can cause a fire in the wiring. The use of specialized pliers ensures that the force is applied exactly at those points where it is necessary to create a “cold weld” of metals.
⚠️ Attention: Never use regular pliers to crimp NShVI or NShVI2 tubular ferrules. This leads to flattening of the sleeve and loss of contact elasticity, which, in conditions of vehicle vibration, is guaranteed to cause a chain break in a short time.
There are two main types of compression mechanisms: ratchet and non-ratchet. Ratchet mechanism does not allow the tool jaws to open until the full compression cycle has been completed. This eliminates the human factor and ensures that you do not pull out the wire halfway, resulting in a weak contact. Ratchetless models require more experience and a feel for the material, but allow you to adjust the compression force, which is sometimes necessary when working with non-standard alloys.
Using a ratcheting tool is the only way to guarantee the same quality on hundreds of joints without tiring the technician.
Classification of crimping pliers and their purpose
The market offers many modifications of the tool, each of which is tailored for a specific type of task. For an automotive electrician, the most relevant models are those that work with soft multi-core wires, typical for the on-board network. The choice of a specific type depends on what kind of tips and the terminals you plan to mount most often.
One of the most popular types is sleeve tip pliers (NSHVI). They have semicircular cutouts in the jaws, which, when compressed, form a perfect oval or square (depending on the model), tightly enclosing the bundle of wires. To work with male and female terminals, as well as ring and fork lugs, universal models with a set of replaceable dies are used.
- 🔧 Pliers for NShVI: Designed exclusively for insulated and non-insulated bushings, they provide an ideal compression profile.
- 🔧 Universal crimpers: equipped with several slots of different sizes to work with different types of terminals in one tool.
- 🔧 Hydraulic presses: used for crimping large cross-section power cables (from 16 mm² and above) used in starter circuits.
- 🔧 Automatic strippers with crimp function: combine stripping and crimping, convenient for mass work with wires of the same type.
Special attention should be paid to tools for working with corrugated tubes, which are often used to protect wiring harnesses. Although this is not exactly an electrical contact, the correct crimping tool for such elements speeds up the assembly of the harnesses significantly. It is important to understand that one universal tool can rarely perform all types of work efficiently.
Technique for working with sleeve tips (NSHVI)
Working with stranded copper wires requires preliminary preparation. Unlike a single core, a bundle of thin wires can become fluffy, making it impossible to insert them into a terminal or connector. Usage sleeve tips (NSHVI) solves this problem by assembling the cores into a monolithic cylinder. Their installation requires special pliers with the appropriate jaw profile.
The process begins with stripping the insulation. The length of the stripped area must exactly match the length of the metal part of the tip. If you strip too much, bare copper will remain exposed, creating the risk of a short circuit. If it is too small, some of the cores will remain under the insulation and will not enter the sleeve, which will reduce the contact area. It is considered optimal to protrude the insulation 1-2 mm beyond the metal sleeve after putting it on.
For precise stripping, use a stripper with an adjustable cut length rather than a knife. It is easy to damage several outer cores with a knife, which will reduce the throughput of the wire.
After putting on the tip, the wire is inserted into the corresponding socket of the pliers. Tool for NSHVI usually has two cutouts of different sizes for different sections. When compressed, the jaws close, forming a reliable connection. The characteristic click of the ratchet signals the end of the cycle. An attempt to remove the wire prematurely is blocked by the mechanism.
The quality of the resulting connection is easy to check visually and mechanically. The tip should not turn on the wire, and the wire should not be pulled out with moderate force. The metal part should fit tightly around the cores, leaving no gaps. For automotive wiring subject to vibration, this is the only acceptable way to trim the ends of multi-core cables before connecting them to screw terminals.
Working with terminals and bare lugs
More complex tasks face the technician when installing detachable terminals (Faston type) or ring contacts. Here, the form of compression plays an even more important role, since incorrect bending of the terminal tabs can lead to the fact that the mating part simply does not fit or holds weakly. For such work, pliers with profiled jaws are used, often shaped like the letter “C” or “O”.
An important aspect is the selection of the matrix size for the wire cross-section. Crimping a thin wire too hard in a large die can tear the metal, and crimping a thick wire too weakly in a small die will not produce the required force. High-quality tools often have cross-section markings (for example, 0.5-1.5 mm², 1.5-2.5 mm²), which simplifies the selection of the working groove.
⚠️ Attention: When crimping non-insulated lugs, make sure that the wire insulation does not get inside the metal sleeve. This will create a dielectric layer, and there will be no contact, despite the apparently tight compression.
To work with insulated terminals (where the tip is already covered with colored plastic), pliers with a three-leaf matrix are used. They crush the metal and at the same time fix the plastic cuff on the wire insulation, creating additional mechanical fixation. This is especially useful in vibration environments, preventing the wire from being pulled out of the terminal.
The secret to perfect crimping of insulated terminals
Use pliers that have a separate stop for the plastic “skirt” of the terminal. This prevents crushing of the contact tab itself, maintaining its geometry for a reliable connection with the mating part.
Comparison of tool manufacturers and models
The brand you choose often depends on your budget and how often you use the tool. For one-time work in the garage, budget models are suitable, but for daily use in the service, the savings can come at a cost. There are several groups of manufacturers on the market, each of which occupies its own niche.
The professional segment is represented by brands like Knipex, Wiha or Stahlwille. Their tools are made from high-quality tool steel, hardened to a hardness that allows them to hold an edge and sharpen jaws for years. The mechanism of such pliers works smoothly, without backlash, even after thousands of cycles. The price of such models is high, but it pays off with the speed of operation and the absence of defects.
Middle price segment, including brands like Jonnesway, Ombra or Force, offers good value for money. This is an excellent choice for equipping a private garage or small service station. The metal here may be a little softer, and the casting accuracy is a little lower, but for most automotive tasks their capabilities are quite sufficient.
| Brand | Class | Features | Resource (cycles) |
|---|---|---|---|
| Knipex | Premium | Perfect geometry, forged steel | > 100 000 |
| Jonnesway | Average+ | Good ergonomics, accessibility | ~ 50 000 |
| Force | Medium | Reliability, wide range | ~ 30 000 |
| Budget | Initial | Low price, possible backlash | < 10 000 |
When choosing, you should also pay attention to the ergonomics of the handles. Automotive electricians often require working in tight spaces, putting your hands up in the air, or working in tight spaces. Rubberized, non-slip handles and the compact size of the tool significantly reduce fatigue.
Typical mistakes and their consequences
Even with a good tool, you can make mistakes that will ruin all your efforts. The most common of them is the incorrect choice of the cross-section of the tip relative to the wire. Using a 2.5 mm² lug on a 1.5 mm² wire will cause the contact to dangle. Conversely, trying to stuff a thick wire into a small sleeve will damage the wires.
Another common mistake is double crimping. Some craftsmen, not trusting the first compression, try to compress the tip again, turning it 90 degrees. In the case of sleeve terminals, this is acceptable and even recommended for forming a square, but for terminals this can lead to deformation and disruption of the geometry of the contact pad.
- 🚫 Core twisting: Before putting on the tip, you should not twist the wires with your fingers, this will disrupt their structure.
- 🚫 Remaining insulation: even 1 mm of insulation inside the sleeve dramatically increases the contact resistance.
- 🚫 Improper use: An attempt to bite off the wire with crimping pliers (if they are not combined) will damage the tool.
⚠️ Attention: Never use crimping pliers to cut wire unless the manufacturer's instructions explicitly indicate that the model is equipped with a cutter. The hardness of the crimping sponges is not designed to withstand biting; the cutting edge will crumble.
Oxidation is also worth mentioning. If you work with aluminum wires (which is common in older cars), you need special tools and a lubricant that prevents oxidation. It is also advisable to treat copper wires with quartz-vaseline lubricant after crimping, especially if the connection will be in a humid environment.
Tool maintenance and storage
To crimping tool served for a long time, it needs to be looked after. After work, it is recommended to wipe the working surfaces with a dry cloth, removing any remaining metal shavings or dust. Periodically, it is useful to lubricate the hinge joint with light machine oil so that the movement of the jaws remains smooth.
The tool should be stored in a dry place, preferably in a case or case, to protect the jaws from shock and corrosion. A fall of pliers on a concrete floor can lead to microcracks in the metal or disruption of the geometry of the jaws, which will make the tool unsuitable for high-quality work.
Regularly checking the calibration is also a good idea. Take the test lead and ferrule, make a crimp and check the pull-out force. If you are not happy with the results, it may be time to replace the tool or have it professionally serviced.
Frequently asked questions (FAQ)
Is it possible to crimp a wire without special pliers?
Technically, you can use pliers, but the quality of the connection will be poor and unstable. For temporary repairs this is acceptable, but for permanent use in a car where there is vibration, such contact will quickly collapse. It is better to use at least simple universal pliers.
What is the difference between NSHVI and NSHVI2?
NShVI is designed for crimping one wire, and NShVI2 is for crimping two wires at the same time. The NSHVI2 tip has an elongated metal part to cover two bundles of cores. You cannot crimp two wires into a lug for one wire - they will not fit or the contact will be poor.
Do I need to tin the wire before crimping?
Absolutely not. Tinned (soldered) wire becomes monolithic and loses flexibility. At the point where it exits the tip, during vibration, the tinned part will act as a lever and quickly break the wires. Only pure copper can be crimped.
How to determine the wire cross-section for selecting pliers?
The cross section is usually written on the wire insulation (for example, 1.5, 2.5). If there are no markings, you can use a table of correspondence between core diameter and cross-section, or visually compare the wire with reference samples on the tool. An error in choosing the size will lead to poor contact.