How a Sewing Machine Works
Have you ever wondered what was inside your sewing machine? If you were to take the casing off, you would find an intricate setup of shafts, gears and mechanics that all work together to make your sewing machine run. Today, we’re going to take an up-close look at the part of the sewing machine where all the magic happens — the needle and bobbin assemblies — to see how stitches are formed.
View of the needle on the downstroke. Shown without thread or bobbin.
Creating a Lock Stitch
To understand how a stitch is made, we’re going to take a look directly under the needle plate. Beneath the sewing machine’s needle is a bobbin, which is a small spool of thread. The bobbin sits in a shuttle that moves with the rhythm of the machine.
When you engage your sewing machine, the needle is pushed down through the fabric. Once the needle reaches its deepest level, it begins its ascent back through the fabric. As the needle begins to pull up, the friction of the needle against the fabric and thread forces the thread out one side of the needle, creating a loop. The needle has a groove on one side, which allows the thread to slip without friction. Since the thread can slip on that side of the needle, only one loop is created on the opposite side of the groove. At this exact moment, a hook on the bobbin shuttle catches the loop of thread and interlocks it with the thread feeding off the bobbin. The two threads then interlock around the fabric pieces to create a lock stitch.
Some sewing machines, like the Sailrite® Ultrafeed® LS and LSZ, have a walking presser foot. This walking foot mechanism helps to ensure that proper stitches are created. The walking foot is timed with the machine to help pull the fabric into position for needle puncture on the downstroke and to hold it in place through the upstroke. By holding the fabric in place as the needle rises, the walking foot helps to ensure that a proper loop is created under the fabric.
Thread loop being hooked by the bobbin shuttle. Shown without bobbin thread.
When Timing Goes Bad
This process requires exact timing within the machine’s movement to successfully create a stitch. When the timing in your sewing machine goes awry, it results in dropped stitches or other problems. If the hook reaches the loop too early or too late, a stitch is not created. Similarly, as the needle rises, if the fabric is not secure against the machine, it will rise with the needle and a loop won’t be formed.
If you experience dropped stitches with your sewing machine and you suspect timing issues, check your machine’s guidebook for more information. The Sailrite Ultrafeed Guidebook contains detailed troubleshooting solutions, including how to reset your machine’s timing.
Learn more about Sailrite Sewing Machines, how they work, and all of their great features in our sewing machine category.