A large number of sewing machine repairs are related to sewing machine tension issues. In previous posts, we have discussed the basics of tension, threading, and adjusting the bobbin tensions.
In this post, we will quickly review the adjustment of the upper tension. As we do so, keep in mind that balancing tensions requires the pull from the bobbin be equal with the pull from the top thread. Whenever top or bottom is greater, the thread will pile up on that side of the fabric.
You can also learn these vital skills by taking a sewing machine repair course or a series of sewing machine repair courses.
The upper sewing machine tension assembly consists of a set of tension discs that press from opposite sided against the upper thread to create resistance. The assembly also includes an internal tension spring, a pin to relieve pressure when you lift the presser foot, an adjusting knob, and a tensioning spring to maintain consistent thread position. The tensions assembly is usually held in place by a set screw. The screw may be reached through the opened needle bar cover or by removing the top cover.
The tension assembly on older sewing machines is prone to rust and surface deterioration. This may require parts or the entire assembly to be replaced.
Sometimes grit and grim gum up the pressure release pin. This is solved by disassembling the tension assembly and thoroughly cleaning it. When you reassemble the upper tension assembly, a drop of oil on the pressure release pin is advisable, but do not get oil on the tension discs.
Also look for burrs, knicks, or thread scores that may snag the thread or alter the tension. These will need to be removed, buffed, or otherwise eliminated.
A vital key to sewing machine repair is remembering how things go back together. In some cases, it is easy to take things apart, but if you get careless... It might never go back together the way it should. Therefore, when you are repairing sewing machines, always take the parts you remove and place them neatly in their proper order in a safe place. When you are ready to reassemble the parts, just reverse the disassembly process and you will get it right every time.
To adjust the upper tension, simply turn the tension adjust knob. Turn it to the right to increase tension. Turn it to the left to decrease the tension. "Righty tighty, lefty loosy."
When you finish adjusting the tensions, adjust the knob so that it looks right to the user. Many users believe a certain number (3 or 5) is essential. Actually, this is only for cosmetic purposes. But often you can not convince the user otherwise.
In our next post, we will examine several trouble spots affecting tensions and sewing machine repair.