Plastic Bobbins vs Metal Bobbins

Difference Between Plastic Bobbins and Metal Bobbins

Plastic Bobbins vs Metal Bobbins

It’s commonly heard that plastic and metal bobbins shouldn’t be used interchangeably. If there are two bobbins and everything between them such as shape and size is the same yet one is made of metal while the other is made of plastic, you shouldn’t use one as an alternative to the other.

The plastic had been introduced for only a few decades. It’s production cost is cheap, thus mass produced and available at a cheap price. For reasons like these, you’ll always find at least one plastic alternative for most of the things that used to be built with metal. Bobbins aren’t different. They’ve been made with plastics too.

The word that you hear that plastic bobbins and metal bobbins should be used in different places actually has a few reasons. If you, unknowingly, interchange between two of these, you can create some issues for your sewing machine. We’ll talk about those reasons so that you get a clear idea on the uses of both bobbins.

Differences Between Metal Bobbins and Plastic Bobbins

There are several differences between these two and we’ll talk about each of them on a point by point basis-

Tensile Strength

Well, metal has more tensile strength a.k.a. tension holding capacity than plastic. And this is where the problems begin.

When you load a bobbin on a sewing machine and start the machine, the movement of the machinery inside creates tension in the string attached to the bobbin. Usually, if the bobbin is made of metal then there’s nothing to worry about as it has enough tension holding capacity and won’t bend or break down.

But, if instead, the bobbin is made of plastic and has to face the same tension as the metal one then this pulling movement can put a toll on the plastic and bend the shape. If the bobbin is made of thin plastic then there are high chances of it breaking down under the load.

Case Size

Metal bobbins have a standard size and the cases in a sewing machine are built accordingly. You can try to fit a plastic bobbin on a metal case and it will seem to fit, even if it doesn’t completely. Until you notice clearly, you might totally miss on the fact that the plastic bobbin isn’t quite fitting on the metal’s case.

What happens in a case like this is because the shapes of both the bobbin and the case are different, the tension on the string might bend the shape of the bobbin unevenly. Or maybe the bobbin could get broken on one side since the case can’t hold the bobbin well in place.


Metal is durable than plastic, there are no confusions here. With a good quality metal bobbin, you can rest assured that it’s going to last a long time even if you handle it rough. You can increase the tension level of the thread and still there would hardly be chances of the metal bobbin deforming or breaking apart.

These are usually made of steel or aluminum or a mix of these. These metals, in their nature, are long lasting and can perform well under a variety of situations. The pressure holding capabilities of these are unmatched with the plastic ones. However, one problem is that they’re expensive. It’s expected.

But what about the plastic ones? Are they bad? No. Everything has its own place. A piece of plastic will never go rusty, unlike metal. With a metal bobbin, you have to worry about keeping it away from liquids. It has to be kept dry and not in a humid place to avoid rust formation.

But with a plastic bobbin, chances of rust formation is unlikely. Well, there are chances if you keep it in contact with a rusty metal but chances of that are not much, practically.


You’ve likely noticed that the modern sewing machines use plastic bobbins more than they use metal bobbins. They are basically designed in this way. However, there is a good side to this design. Because plastic is cheap, you overall have to spend quite less regarding the bobbin purchases.

However, there’s a misconception that since metal is stronger than plastic and costs more, should it be a better, premium choice for the bobbins? Not really. The plastic bobbin cases are designed only for plastic based bobbins and not metals. You can use metal if you like but this may cost you some damages with your sewing machine.

Metal and plastic bobbin cases have different tension levels. If you hinder their natural movement, you may create an unintended effect inside your sewing machine that you might not even know about. Just because you’re using something more durable doesn’t mean it’s going to suit the machine well.

Also, many metal bobbins are unlikely to fit in the newer plastic cases. Putting these in the plastic cases can also put your sewing machine at some risk. It’s better if you avoid doing this and follow what the case is made for.

The opposite scenario also happens. Some people think of saving money by using plastic bobbins on metal cases. Initially, it may seem like a good idea since it’s allowing the user to save a few bucks. But it’s a bad idea and will likely damage the sewing machine in the long run.

Caution – The fact about universal bobbins

You might have seen some bobbins named as universal bobbins. It’s not really true. Different sewing machine manufacturers make variations in the bobbin case sizes. And for this reason, the bobbin sizes should be followed according to the cases’.

Always follow the bobbin size for a given sewing machine. One size cannot fit all. Universal bobbin is basically a marketing trick. Follow the class sizes of bobbins.

Final Words

The best way to know if you can use a metal bobbin in a plastic bobbin case or the other way round is by checking the sewing machine’s manual. Follow the manual correctly and you can save yourself from many common issues regarding the bobbins.

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