Bobbins · Skipped stitches

The lowest bobbin tension

Low tension on the bobbin thread is required in many situtations, in particular for zig-zag, buttonholes and embroidery, or also for straight stitch to make a flexible stitch that stretches with fabric (think knits and jersey!). Each machine has its own limit to how low the bobbin thread tension can go before the stitches get wobbly and uneven. This limit is governed by many factors working together, and it is not always possible to address them all. But one such factor is very much under our control: the tension regulating screw.

The following applies to all machines with a more advanced shuttle than that of Singer 12. In Singer 12, bobbin thread tension is regulated by winding the thread around a pin… Let’s not talk about that. Let’s talk about all those machines, long bobbin or round bobbin, that have a spring to regulate bobbin thread tension.

Different shuttles and bobbin cases look differently and appear to have nothing in common, yet they all have a strip of metal that presses down on the thread creating thread tension. And they all have a screw that regulates how hard the spring presses down on the thread.

You screw it into the hole to increase tension, or raise it out of the hole to lower tension. At some point the screw head starts rising too far out of the bobbin case, so that thread gets caught on it as it passes around the bobbin case on each stitch – and you start getting thread pulls.

The solution to the problem is to adjust the spring. The spring has a bend in it that can become deformed over time, so it is not working properly any longer. Also dirt and lint underneath interfere with it.

The thing to do is to remove the spring and to clean it first of all, as well as polish the spring and the entire shuttle. The screw head may not be the only thing that the thread is catching on to! (Don’t forget to polish the screw head as well – it often gets scarred by the screw driver.)

After cleaning and polishing, put the spring back on and try different tensions. Chances are, low tension now works a lot better too – including being able to reduce it and not get any thread pulls.

But if the thread pulls persist, then may be the spring has gone out of shape and needs adjusting. Remove it again and bend it outwards slightly – to reduce the curvature. But only slightly!! The goal is to allow the screw to go further in while still only pressing very gently on the spring.

Put the spring back on, try again.

Eventually with trial and error you’ll figure out the correct spring shape for your shuttle. It may well be that when you bend it outwards far enough to allow sewing with very low tension, it won’t be able to deliver high tension any longer. If that’s the case, the solution is to have another bobbin case adjusted for higher tensions, but it won’t be able to do that very low tension for you.

It is actually a good idea to have several bobbin cases for each machine, set up for different bobbin thread tension. Bobbin cases are usually easy to find, also for vintage and antique machines, except of course for rare models – but those are often less practical for daily sewing anyway. I keep spare bobbin cases wherever I can – for different adjustments, but also just as a pixie deterrant. Pixies hate backups, you know. 😉

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3 thoughts on “The lowest bobbin tension

  1. Hi Elena, I am trying figure out what type of shuttle and bobbin my vintage New Cottage vibrating shuttle treadle sewing machines needs so I can order it.

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    1. Hi Esta, sorry, I have no idea. I believe the only reproduction shuttles that are available, are Singer shuttles. I seem to have heard that New Cottage was a brand owned by New Home, but I am not sure. New Home also produced several types of vibrating shuttle machines, with different shuttles.

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