Poor crimping of insulated ferrule NSHVI-2 4mm² Press jaws with adjustable force are the most common cause of overheating of contacts in automotive wiring. If after crimping there are gaps on the sleeve, and the insulation cracks when bent, the problem is not in the wire, but in an incorrectly selected tool or a violation of technology. Even professional pliers Knipex PZ 63 will give a defect if you do not take into account the cross-section of the core, the type of tip (NSHVI, NKI, NSHPI) and insulation material (PVC, nylon, heat shrink).
In 80% of cases of car electrical equipment malfunctions, it is not the wire itself that is to blame, but poor-quality crimping. For example, using universal pliers for non-insulated ferrule sleeves NSHVI leads to the fact that the insulating cuff is not fixed, and the core is crimped only on 60% of the area. This creates a high transient resistance, which after 3-6 months of operation causes the fuse or relay block terminals to melt. To avoid such consequences, you need to understand the types of press jaws, their markings and the nuances of working with different tips.
Types of press jaws for insulated tips: how they differ and which ones to choose
All press jaws for insulated tips are divided into three categories according to the principle of operation: pliers (with manual force), lever (with pressure booster) and hydraulic (for industrial volumes). For automotive wiring, the first two types are optimal. Hydraulic ones are used at service stations for crimping power cables with a cross-section of 16 mm² or more.
The key difference is in the crimping mechanism:
- 🔧 Pliers (for example, Jonnesway PT-3516) - simple, compact, but require physical effort. Suitable for one-time work with wires up to 6 mm². The main disadvantage: uneven pressure when pressed lightly.
- ⚙️ Lever (Knipex PZ 63, Weicon Crimpfox) - have a built-in pressure amplification mechanism. Provide uniform crimping along the entire perimeter of the sleeve. Optimal for regular use.
- 💧 Hydraulic (HT-708B) - used for cables 10–50 mm². They are rarely used in cars, only when tuning sound or installing winches.
For 90% of auto electrical tasks, lever pliers with adjustable dies for different sections are sufficient. For example, model Knipex PZ 63 01 supports tips NSHVI from 0.5 to 6 mm² and has color-coded slots for quick selection. Important: some cheap pliers (for example, no-name from AliExpress) do not have force calibration, which leads to “under-pressing” or cut wires.
If you work with aluminum wires (for example, in old foreign cars), choose pliers with a trapezoidal matrix profile - they fix soft metal better.
Marking of tips: how not to confuse NShVI, NKI and NSHP
An error in choosing the type of tip leads to the fact that even professional pliers will not be able to provide high-quality crimping. Explanation of markings:
- 🔹 NSHVI — pin sleeve insulated tip. Suitable for single-core wires. For example, NSHVI-2 4mm² means: pin terminal for wire with a cross-section of 4 mm², with an insulating sleeve.
- 🔸 NKI — ring tip insulated. Used for bolted connections (ground, battery terminals). Marking NKI 6-10 — for wires 6–10 mm².
- 🔶 NSHPI — pin tip, flat, insulated. Needed for plug connectors (for example, in a relay block).
Important: NSHVI and NSHPI They are similar in appearance, but have different crimp profiles. If you use the matrix for NSHVI on NSHPI, the contact pad is deformed incorrectly, which leads to poor fit of the terminal in the connector. For example, in Ford Focus 2 often used NSHPI-2.8 to connect sensors, and their crimping requires a special matrix with a flat profile.
| Tip type | Application | Wire cross-section, mm² | Crimping type |
|---|---|---|---|
| NSHVI | Pin connections (terminals, connectors) | 0,5–10 | Round or Hexagonal |
| NKI | Bolted connections (ground, battery) | 1,5–50 | Ring |
| NSHPI | Male connectors (relays, sensors) | 0,5–6 | Flat |
How to properly crimp insulated lugs: step-by-step instructions
Even with professional pliers, you can ruin the connection if you do not follow the technology. Let's look at the process using crimping as an example. NSHVI-2 2.5 mm² on the wire for connecting the radio:
- Removing insulation. Use a stripper with adjustable cutting depth (for example, WS-04A). The length of the exposed core should be equal to the depth of the tip sleeve. For NSHVI-2 2.5 mm² this is usually 8–10 mm. If the core is shorter, the contact area will decrease; if it is longer, the insulation will be crimped and crack.
- Matrix selection. On pincers Knipex PZ 63 for a cross-section of 2.5 mm², a socket with a blue mark is used. Check that there are no burrs or traces of corrosion on the matrix - they damage the tip insulation.
- Positioning. Insert the tip into the matrix so that the insulating collar rests against the stopper. Place the core flush with the edge of the sleeve.
- Crimping Squeeze the handles of the pliers until they stop. For lever models, a click should sound, which means that the force has been achieved. Don't release the handles until you hear a click!
After crimping, check the connection:
- 🔍 Visually: the insulating cuff must be deformed evenly, without cracks.
- 🤏 Tactile: the sleeve should not scroll on the core.
- 📏 Geometry: when viewed from the end, the compressed part should have the shape of a regular hexagon (for most dies).
☑️ Checking the quality of crimping
A typical mistake: crimping “in two steps” (first the sleeve, then the insulation). This leads to displacement of the core inside the tip and an increase in resistance. All modern mites (for example, Weicon Crimpfox 6) are designed for simultaneous crimping of both the sleeve and the insulation.
Top 5 mistakes when working with press jaws and how to avoid them
Even experienced auto electricians make mistakes that shorten the life of the connection. Here are the most common:
- Wrong choice of section. For example, crimping the tip NSHVI-2 4 mm² on the wire 2.5 mm². As a result, the sleeve is not completely crimped, but the core “dangles” inside. Consequence: heating and melting of the terminal after 1–2 years. Solution: Always check the wire cross-section and tip markings.
- Using unsuitable pliers. Crimping NKI pliers for NSHVI leads to deformation of the ring and the inability to put it on the bolt. Solution: for NKI you need pliers with a round matrix profile (for example, HT-308D).
- Repeated crimping. If it doesn't work out the first time, many try to squeeze it again. This leads to microcracks in the vein. Solution: if the crimp is unsuccessful, cut off the tip and take a new one.
Two more critical errors:
- ⚡ Ignoring color coding. On pincers Knipex and Weicon Each nest has its own color corresponding to the section. If you mix it up, for example, crimp a 1.5 mm² wire into a 4 mm² socket, the contact will be unreliable.
- 🔥 Working with oxidized conductors. Aluminum wires (found in old Mercedes or Volvo) before crimping must be cleaned with a special paste (for example, Weicon Aluminium-Paste). Otherwise, the oxide film increases the resistance.
What to do if you don’t have the right size pliers?
If you don’t have pliers on hand for a cross section of 10 mm², but need to crimp NKI 10, you can use the nearest larger socket (for example for 16 mm²), but only with lever pliers, which limit the effort. In this case, the crimp will be incomplete, but temporarily acceptable. However, such a connection must be replaced as soon as possible.
⚠️ Attention: Never use pliers or a hammer to crimp insulated lugs. This leads to pinpoint pressure, which destroys the core and does not ensure the tightness of the insulating collar. In automotive wiring, such connections become a source of short circuits after 3–6 months.
Comparison of popular press jaw models: what to choose for your car
The following models are suitable for working with automotive wiring (cross section 0.5–10 mm²):
| Model | Type | Section, mm² | Features | Price, rub. |
|---|---|---|---|---|
| Knipex PZ 63 01 | Lever | 0,5–6 | Color coded, click when fully crimped | 8 000–10 000 |
| Weicon Crimpfox 6 | Lever | 0,5–6 | Replaceable dies, ergonomic handles | 7 500–9 000 |
| Jonnesway PT-3516 | Pliers | 0,5–10 | Budget option, no click | 2 500–3 500 |
| HT-308D | Lever | 1,5–16 | Suitable for NKI and power cables | 5 000–6 500 |
Suitable for one-time work (for example, installing an alarm system) Jonnesway PT-3516. If you are a professional auto electrician, take Knipex PZ 63 or Weicon Crimpfox - they will pay off due to the absence of defects. Model HT-308D relevant for working with power circuits (for example, when installing a winch or inverter).
When choosing, pay attention to:
- 🔧 Matrix material. Better - hardened steel with anti-corrosion coating. Cheap pliers with aluminum dies wear out quickly.
- 🎯 Crimping accuracy. For high-quality models, the tolerance on the sleeve diameter does not exceed 0.1 mm. You can check with a caliper.
- 🔄 Replaceable matrices. If you plan to work with different types of tips (NSHVI, NKI, NSHPI), choose models with replaceable inserts.
To work with aluminum wires (for example, in old foreign cars), choose pliers with a trapezoidal matrix profile - they fix soft metal better.
Crimping without special pliers: temporary solutions and risks
If you don’t have press pliers at hand, and the connection needs to be made urgently (for example, on the road), you can use alternative methods. However, they all have limitations:
- Pliers + hammer.
- ✅ Suitable for NKI (ring tips).
- ❌ Cannot be used for NSHVI - the insulating cuff will crack.
- ⚠️ Risk: Uneven pressure may cut veins.
- Vise + mandrel.
- ✅ You can achieve uniform crimping if you use a mandrel (for example, a bolt of a suitable diameter).
- ❌ Requires precise centering - when displaced, the sleeve is deformed crookedly.
Temporary crimping without pliers is only permissible for emergency repairs. For example, if a ground wire comes off along the way, you can crimp NKI-6 pliers, but such a connection must be replaced as soon as possible. Alternative methods are not suitable for continuous use - they do not ensure the tightness of the insulating cuff and uniform pressure on the core.
⚠️ Attention: If you are crimping a tip without special pliers, be sure to check the connection with a multimeter in continuity mode. The resistance between the end of the wire and the sleeve should be close to 0 ohms. If the readings jump or exceed 0.5 ohms, the crimp is of poor quality and needs to be redone.
Caring for press jaws: how to extend their service life
Jaw presses are precision tools that require regular maintenance. Basic rules:
- 🧴 Lubrication. After each use, clean the dies from oxides and apply a thin layer of grease (for example, WD-40 Specialist). This prevents corrosion and jamming of the mechanism.
- 🔨 Calibration Check the crimp force on the test tip every 6 months. If the sleeve is crimped unevenly, the pliers need adjustment (in workshops this is done on a special stand).
- 🚫 Prohibited actions.
- Do not crimp tips with a larger cross-section than the pliers are designed for.
- Do not use pliers as wire-cutting pliers.
- Do not store the instrument in a damp place (such as an unheated garage).
If the plier matrices are worn out (burrs or wear appears), they can be replaced. For example, for Knipex PZ 63 Matrix repair kits are sold (article no. Knipex 01 01 200 SB). The cost of the kit is about 2,000 rubles, which is cheaper than buying new pliers.
How to check matrix wear?
Take a new tip NSHVI-2 2.5 mm² and crimp it. Then cut the sleeve lengthwise and inspect the cross-section under a magnifying glass. If it is clear that the core is compressed unevenly (there are gaps), the matrices are worn out.
FAQ: Frequently asked questions about press jaws for insulated tips
Is it possible to crimp non-insulated tips with pliers for NShVI?
Technically it is possible, but the quality will be worse. Pliers for NSHVI have an additional protrusion for crimping the insulating collar, which prevents the uninsulated sleeve from being uniformly deformed. For NSHV or NK It is better to use specialized pliers (for example, Knipex PZ 55).
What color marking on the Knipex PZ 63 corresponds to the 4 mm² section?
On the model Knipex PZ 63 01 cross section 4 mm² corresponds to red nest. Full color description:
- Yellow – 0.5–1 mm²
- Blue – 1.5–2.5 mm²
- Red – 4 mm²
- Black – 6 mm²
What should I do if, after crimping, the ferrule rotates on the core?
This means that the crimping was performed poorly. Causes and solutions:
- Insufficient force - repeat crimping in correct socket.
- Incorrect cross-section - check that the wire and lug match.
- Worn dies - replace them or use different pliers.
If the tip is already installed and scrolls, it needs to be cut off and a new one crimped on.
Is it possible to crimp stranded wires in NSHVI?
No, NSHVI are intended for single-core wires only. For multi-core use ferrules NSHVI(m) (for example, NSHVI(m) 2.5-8) or pre-tin and crimp into a regular sleeve. Otherwise, the wires will be flattened and the contact will be unreliable.
How to check the quality of crimping without special equipment?
Take the crimped end and pull the wire with a force of 10–15 kg. If the tip does not fly off or spin, the crimping is done correctly. Also inspect the insulating collar - it should be uniformly deformed, without cracks. For an accurate check, use a multimeter: the resistance between the end of the wire and the sleeve should be < 0.1 Ohm.