Ferrules, how and why to use them

electrical ferrulesWant to improve your electrical wiring contacts? Meet the electrical ferrule.

If you’ve ever pushed a bare wire into a terminal block, tighten the screw only to find sometime later the connections fail this is for you.

Terminal blocks, aka connection terminal or terminal connector and their equivalent PCB blocks, where a screw is used to secure a connect wires within a insulated frame, are incredibly useful for joining wires or attaching a wire to a PCB and often a much easier and quicker solution than soldering.

I use them all over my layouts and am a big fan of the Snaps EZ wiring connector for the Tortoise Slow Motion Switch Machine point motors.

But stripping the wire, just unscrewing the terminal, pushing exposed conductor cabling into the hole and tightening the screw again can damage the wire, reduce their lifespan and decrease current flow.

For starters, crushing the wire between the screw and conducting metal can separate the fine strands, leaving them prone to snapping off. And, if the wire is moved around a lot, the strands can break at the join. There is also the possibility that with the insulating plastic coating removed, oxidisation can occur further reducing conductivity.

But rather than throwing out connection terminals and revert back to soldering connections for terminal ends, I use Ferrules.

What are ferrules?

Electrical ferrules are like the plastic sleeve on boot laces. Invented in the 1960s, they are metal tubes into which stranded wire is pushed to secure the connection and protect it.

The exposed wire is pushed into the ferrule where it is clamped tight using a crimping tool (see below) and the metal sleeve then inserted into the terminal block.

A plastic collar provides additional protection.

The benefits of ferrules

The advantages of using ferrules are obvious once you use them.

The fine strands of the wire are kept together in the barrel where they maintain the best contact with the conductor in the terminal block and don’t get squeezed out of place, break off or oxidise.

Additionally, the plastic collar provides extra insulation around any exposed wires that accidentally fall outside the connecting terminal receptor while also protecting the strands when the wire is being pulled or removed.

Electric ferrule sizing and colours for model railway wiring

Ferrules are available in different sizes to match wire sizes, with the colour typically indicating the intended wire size. This is defined by the German national standards organisation and defined in DIN 46228.

The ferrule colours for wire sizes commonly used on model railways are:

Wire size Ferrule colour
20 AWG – .5mm White
18 AWG – .75mm Grey
17 AWG – 1mm Red
16 AWG – 1.5mm Black
14 AWG – 2mm Blue
12 AWG – 4mm Grey

ferrules point motorI now use them religiously around the majority of my layouts and can’t fault them and love the improved connections they give. Especially as I usually get my wiring wrong the first time or want to improve it and frequently end up rewiring. This unscrewing, pulling and re-screwing of the terminal blocks often results in frayed wires that don’t they give me the best electrical conductivity.

Ferrules can be purchased here (it’s worth buying in bulk as you get through a lot more than you expect, or is that just me?).

So far, the best crimping tool for Ferrules is this one from Amazon. (US readers please use this link). It’s easy to operate, crimps correctly and grips the ferrule on four sides while operating and feels reassuringly well built.


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