Thread Break Sensor

Many Handi Quilter machines are equipped with a thread break sensor. The sensor lets you know with an audible alarm that your thread is broken. This can be especially useful to Pro-Stitcher users. The sensor will sound the alarm and in the case of Pro-Stitcher, stop the machine. I’ve had some questions lately about how it works and why it sometimes gives a false alarm. The alarm is telling me the thread is broken, but the thread is just fine. So let me explain a bit.

How the Thread Break Sensor Works

The thread break sensor is the round device located just above and to the left of the tension knob.

It works by sensing the movement of the check spring. Take a few stitches and watch the check spring go up and down, past the sensor.

If the check spring doesn’t pass by the sensor because the thread has broken and is no longer pulling on the check spring, the thread break alarm will sound.

But My Thread Isn’t Broken!

Tension on the thread will affect the movement of the check spring. For delicate threads like monofilament or metallic or holographic mylar thread, we adjust our tension much lower to achieve a balanced stitch. A very loose tension may mean the check spring doesn’t come down past the sensor at all. On the other hand, a very tight tension might keep the check spring permanently below the sensor. Or if the check spring isn’t oriented correctly, (not installed at the right angle), it may never pass by the sensor. Any of these situations will cause the thread break sensor to sound the alarm.

Common causes and solutions for false thread break alarms

Cause 1: The check spring is not properly threaded. If the thread is not over the check spring it will not move at all and not pass the sensor. You’ll likely notice bad stitch formation too!
Solution 1: Make sure the thread comes up and over the check spring after it exits the tension disks and prior to going under the stirrup guide.

Cause 2: Tension is set too loose. Sometimes fragile threads require us to loosen tension to the point that the check spring is no longer springing back and forth during the stitch cycle or just barely moving.
Solution 2: The thread break sensor should be turned off. We really need the loose tension for some threads and increasing the tension is not an option. So go into settings and turn it off.

Cause 3: The thin check spring has been flexed out, away from the sensor. Since we thread and unthread our machines a lot, it is common for this spring to get bent a small amount, which can effect the sensor. It must be just the right distance from the sensor to get a good reading.

Solution 3:Because the spring is hardened spring steel, it is not easy to bend it back toward the sensor. Instead, the sensor should be adjusted outward, to be as close to the spring as possible without touching the spring. Customer instructions for adjusting the thread break sensor can be found on the website here. Your local retailer would be happy to help with this if you feel like you need help.

Hope this helps you understand your machine a little better!

Happy quilting!