The best tool for crimping ferrule sleeves is definitely a ferrule crimper. But when you don’t have this special tool at hand and you want to terminate a stripped stranded electrical wire, you can use pliers.
However, it is good to mention that you will not get the same quality of crimp with regular pliers as you would with a good ferrule crimping tool. But the outcome is far much better than inserting bare wire strands directly into the connector, nonetheless.
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What is a wire ferrule?
A wire ferrule is a type of metal sleeve (mainly tin-plated copper) for capping the end of a stranded electrical wire. It keeps the wire strands of flex cable from fraying or separating after stripping the insulation.
Once crimped in place, the ferrule tube binds the fine electrical wire strands together to make one solid core. In other words, a ferrule crimp gives stranded wire the quality of solid wire at the connection point. This ensures that you get a quality electrical connection at the electrical terminal.
Benefits of using wire ferrules
As you probably know, flex cables are the number one choice for most electrical applications. Unfortunately, they make the least reliable electrical connection when the bare wire strands are connected directly.
The free strands are difficult to manage and can easily corrode with atmospheric elements to increase resistance. This together with other factors is why you should terminate stranded wire ends with ferrule bootlace terminals.
Wire ferrules or bootlace terminals help manage the loose wire strands of stripped flex cable. They secure all the strands together to provide maximum electrical contact on screw terminals and breakers. This helps improve electrical safety when working with flex cables and reduces the risk of panel failure due to overheating and short circuit incidents from loose wire strands.
Other advantages of terminating stranded wire with ferrule crimp connectors are that ferrules simplify electrical installation work and make the work look neat.
Ferrules vs standard crimp connectors
Wire ferrules and wire crimp connectors do the same job of terminating electrical wire. Their difference is in how the crimping takes place. Ferrules are crimped over the bare wire strands while crimp connectors are crimped onto the insulation after the stripped end.
Another difference is that a ferrule crimp acts as a cap for wrapping the stripped stranded wire whereas a standard crimp or pin terminal serves as a metal extension to a stripped wire end offering different configurations.
Some of the common crimp configurations include the spade, ring, and butt connector types. An example of a standard crimp connector is the terminal lug you find on battery posts or the grounding wire connecting to the chassis on most appliances.
How do you crimp ferrules?
As I mentioned, the best way to crimp ferrule connectors is by using a ferrule crimping tool. This special crimping tool compresses the ferrule tube over the wire strands to keep them intact and eliminate any wiggle that may affect the integrity of the electrical connection.
But when you do not have ferrule crimping pliers at hand, you can try to use regular wire crimpers or any pliers with a crimping feature. However, the results with these alternative tools are not the same as when you use a proper crimping tool for ferrules.
Regular pliers and crimpers do not create a proper cold weld as does a ferrule crimper. But they are better than nothing.
In the next sections, I will share how to install ferrules with ferrule crimping pliers as well as other types of pliers you can use to squeeze ferrules in tricky situations.
How to crimp wire ferrule with ferrule crimping pliers
This is a step by step guide for crimping a ferrule cap with ferrule crimping pliers. But before you start installing ferrules, make sure the wire is not live. You should never install ferrules on live wires!
Step 1: Identify the size of wire you want to crimp.
The size of the wire will help determine what size of ferrule you need. Typically, a ferrule should be the same size as the wire.
Step 2: Select the right size ferrule connector.
Use the size of the flex wire you want to terminate to determine the correct size of ferrule crimp. As mentioned above, the size of ferrule should be the same as the size of the cable. For instance, use a 6 AWG ferrule for a 6 AWG cable. If you have a bunch of wire ferrules and don’t know their sizes, select the smallest ferrule diameter that best fits the wire.
Alternatively, If you are working with insulated ferrules, you can use the ferrule color code chart below. It has all the French and German color codes for ferrules.
Step 3: Strip the wire to the proper length.
The stripped end should be long enough to fit in the ferrule tube. The stripped end should be about 1 cm. But to avoid making mistakes, just measure the length of the ferrule tube and strip away the same length of wire insulation.
Step 4: Insert the stripped wire end into the ferrule terminal.
Give the free strands a slight gentle twist before putting them through the sleeve. The bell-type entry of the ferrule will guide the stranded wire nicely all the way to the insulation so that no conductor is visible.
Make sure the tip of the wire touches the bottom of the tube. If the stripped section is shorter, remove more insulation from the wire with a wire stripper. If the section is longer, cut it to length with a pair of diagonal pliers or ordinary wire cutters.
Step 5: Crimp the ferrule assembly with your crimping tool.
Simply insert the ferrule terminal assembly inside the jaw of the crimping tool and squeeze the handles firmly to crimp. Squeeze them all the way to tightly secure the wire into the ferrule connector.
Step 6: Test the quality of the crimp.
Do a pull or tug test on the crimp to make sure it is tight and will not come off. Pull the crimped part and the rest of the wire in opposite directions.
If the crimped ferrule comes off or if you notice any wiggling, repeat the last two steps. Otherwise, your wire is properly crimped and ready to make a quality electrical connection.
How to crimp wire ferrules with regular pliers
Option 1: Using wire crimpers
When you don’t have a ferrule crimping tool and you need to connect a ferrule terminal onto a flex electrical wire, you can do it temporarily with regular wire crimping pliers. Ideally, the regular wire crimpers are for crimping terminal connectors. Therefore, they are not the most suitable for crimping ferrules and will most likely make a poor crimp. However, they are good in emergency situations nonetheless.
A poor crimp leaves air spaces between the connector and wire. These air spaces can collect atmospheric moisture which may eventually corrode both the wire and connector. Ultimately, the corrosion of a wire terminal results in a poor electrical connection. That is why I would only recommend this method as a temporary solution for crimping wire ferrules.
Step 1: Identify and prepare the wire you want to terminate.
Start by identifying the wire gauge so that you can pick the right ferrule connector. Then strip away the insulation on the end of the wire. About 1 cm.
Step 2: Select the ferrule connector and fit it over the stripped wire end. Ensure all the strands of the flexible wire fit inside the ferrule tube. Also, ensure that the stripped wire goes all the way into the metal tube such that the insulation on the wire only touches the top of the tube.
Step 3: Crimp the ferrule terminal assembly. Place the ferrule assembly between the jaws of the wire crimper and start crimping from the end where the insulation on the wire starts. Crimp all the way to the other end of the metal tube leaving small gaps between the crimps.
Step 4: Do a pull test to ensure that the wire is tightly held in place by the crimped ferrule.
Option 2: Using combination pliers with a crimping slot
Some regular pliers such as the Milwaukee 7-in-1 combination pliers have a wire crimping feature. However, the crimper is for ordinary pin connectors, not ferrule caps. Therefore, you will follow the procedure for Option 1 above to crimp ferrule with these types of pliers.
Although crimping ferrules with ordinary pliers or crimpers is not the best way to crimp them, it helps to eliminate the problems associated with connecting the bare stranded wire to screw terminals.
Some of those problems include the shorting out of equipment by stray wire strands and insufficient surface area for electrical contact. Also, connecting stranded wire on a screw terminal without a ferrule eventually results in a mechanically and electrically weak connection.
If you have worked on electrical industrial panels, I bet you know how much damage a stray wire strand can cause. That is why you should always terminate flexible electrical wires with ferrules or terminal connectors before screwing them on the terminal block.
Frequently Asked Questions
Many people ask if terminating stranded wire with ferrules is a requirement in the US. The simple answer is that wire ferrules are not a requirement in the US but using them is good practice every technician should embrace. In Europe, however, ferrules are a requirement. As such, all electrical equipment connecting flex wire to screw or spring terminals must terminate them with ferrule crimps to get CE certification. So, if you build electrical devices and plan to sell them in Europe, make sure you use ferrule crimps correctly. Otherwise, your device will not pass the CE certification.
There are three types of ferrules: insulated, uninsulated, and twin-wire ferrule. The insulated ferrules are the most commonly used ferrules because they are color-coded.