Why Does My Sewing Machine Thread Keep Breaking?

Hello everyone, today’s vintage sewing machine trivia question is simple. Why does my machine keep breaking thread? The answers we get are not isolated to just the vintage machines or the treadle machines but can apply to any lockstitch sewing machine regardless of bobbin type, even sergers, chainstitchers, and embroidery machines. All sewing machines will break threads from time to time. In order to answer this question, we must first be able to understand the nature of the break so we can accurately prescribe a fix for the symptoms.

why does my thread break

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I thought this might be a good topic for all sewing machine enthusiasts young and old, experienced or inexperienced. It will serve as a reminder to the old and a lesson to the young, and those of us in the middle it’s a retraining because we didn’t learn it well enough the first time or we wouldn’t have spent a weekend trying to find a solution. Yeah, that’s the true point of the post, I had an issue that was gradually getting worse and when it got bad enough I wasted a lot of energy looking for the repair in all the wrong places. I forgot to follow all the steps. The steps act as a flow chart and can quickly eliminate possible causes, thus narrowing the search grid. Here are my suggested steps to follow when posed with questions about thread breakage or when working on a machine with said issues.

Eliminate the thread its self by determining the proper application, and thread integrity. Mismatched upper and lower (bobbin) thread size or types (cotton, silk, monofilament, or polyester) could cause breakage as well as inconsistent stitch quality. Thread integrity pertains to the age and the storage routine of the thread. Cotton thread or cotton-poly blend will get dry and brittle with age. If left to age in the sunlight the process is speeded up by the action of the UV-rays. Brittle or dry rot thread breaks easily when pulled. It breaks easier when the tension loops are crossing each other and sharp bends are created in the formation of the stitch. This type of break will normally be crisp clean looking breaks and will affect the upper thread and the lower thread equally.

If the bobbin thread is breaking check the bobbin case for burrs or needle strikes also check the bobbin tension spring and the bobbin itself for rough edges caused by wear or abuse. Most metal bobbins are stamped and pressed components, this process sometimes leaves rough or sharp edges that may be chafing or fraying the thread. Check bobbin tension to ensure it is sufficient but not overly tight. Check for proper fit of the bobbin to the case and that it is the correct bobbin, properly wound and installed.

If the upper thread is breaking, start at the thread spool looking for loops, curls or snags along the thread path. Check the thread guides for burrs and sharp edges as well as the tension assembly. Check to ensure the machine is threaded properly. Check the presser foot and the needle plate for burrs and sharp edges. With rotary or oscillating hook machines check the hook mechanism for burrs or rough edges. Take appropriate action to smoothly remove and polish any snags, burrs or rough edges.
Trying to render the solution to a problem is very much like solving a puzzle. The harder it becomes to solve the problem the smaller the details you need to look for. As for the issue that I was having, It has been solved, It came down to simply not paying attention to detail. My upper thread was breaking for no apparent reason as I was free motion quilting some Christmas goodies. I did use the steps after a few fails but still with no true defining direction to follow. I was just guessing and hoping it would go away. The solution was proven when enough attention was given to detail. My thread was breaking, yes but how? It was not breaking with smooth sharp edges, it was chafing and fraying as it was pulled apart causing the last few stitches created before breaking to get thinner so thin the thread pulled apart leaving a bushy thick frayed edge on my thread adjacent to the eye of my needle and large enough it wouldn’t fit through the needle. Now I see the details, clearly, the thread was being chaffed and frayed by a burr in the eye of my needle. Simple details, when overlooked, caused me to spend unnecessary time in finding the solution. I replaced the faulty needle and I haven’t broken a thread in a couple days.

My goal for today will have been met if this post makes someone laugh, or helps someone remember the smallest of details offer the biggest solutions. So until we meet again, May your straight cuts be straight and your seams all on point.

Mel made the below graphics as an easy reference to go along with the blog post. Printable Version and PDF Version

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