I cant stand it anymore. These tensions are all screwed up.
This and similar complaints are among the most common grievances expressed by sewing machine users. Excess threads bunch up under the fabric or bubble up on top of the fabric. The stitch may be fine for an inch or two, and then abruptly they screw up and the whole job is ruined.
There are many possible causes of bad sewing machine tension. One of the common causes of improper tension comes from faulty threading of the upper thread or bobbin assembly. Missing a thread guide, threads floating on top of the upper tension discs, or threads missing the bobbin tension can cause havoc with the stitch quality. Rough spots, worn surfaces, lint and debris, burrs on the hook, bad needles, and bad thread can also cause faulty tension.
Properly set tensions should produce stitches with the upper and lower thread locked together in the center of the fabric. When you look at the seam from the top side, you should see a smooth even flow of thread with tiny holes into the fabric. When you turn the fabric over, you should see exactly the same quality stitching as you saw from the top side. The stitches should be snug and show no extra threads on top or bottom.
Tension is simply the resistance created by the sewing machine to guide and manipulate the thread making it do what it is intended. When this resistance is adjusted correctly, the upper thread and lower thread mechanism balance each other. The result is a quality stitch without excess threads where they should not be.
Standing on top of your sewing machine is an imaginary little person. You might call them little people or gnome or leprechaun. He pulls on the thread from the top. Another little person is under the needle plate of your sewing machine. Each one is pulling on their thread. The one that pulls the strongest gets the most thread. If the fellow on top, pulls harder than the one below, you will see little puckers, wobbles, or balls of thread along the top of the fabric. If the little fellow on the bottom pulls harder, you will see bunches of tangled threads underneath the fabric. Only when they pull equally, do you see a proper stitch without excess threads.
Adjusting the tensions on your sewing machine is usually quite easy once you understand what your tension system is suppose to do. Your goal is to modify the drag on the thread until the resistance is equalized top to bottom " bottom to top.
The first thing you should do when you see messed up tensions, is to rethread the upper thread. Are you using a spool cap? Check for any rough spots that might snag the thread. Check for any debris or lint in the tension discs. Before threading the tension mechanism, lift the presser foot. Make sure everything is right. When you reach the needle, tug on the thread. It should draw smoothly with very little resistance. Put the presser foot down and pull again. Now there should be significant resistance.
The bobbin tension is usually more dependable than the upper tension. However, lint and debris can collect under the tension spring. Also if you change the size of bobbin thread, you will need to adjust the lower tension. To make this adjustment look for a tiny slotted screw pressing down on the bobbin tension spring. Turn right to tighten or left to loosen. You may prefer to have a professional make this adjustment if it is necessary.
Next, adjust the upper tension to equalize the lower tension. You may need to rely on some trial and error until you get it just right. Ignore the numbers on the tension dial, unless they are really low or really high. In this case you may need to disassemble the tension assembly to make the repair, or have a technician to do.
Always do a test seam on scrap materials before sewing a finished seam that will be seen. Adjust the tension on the stitch you plan to use until it is properly balanced. Note a straight stitch may appear balanced, but when you go to a zig zag or other stitch, it may not produce your perfect stitch. Always test before sewing your finished seam.
You may notice irregularities on one side of a zig zag stitch and not on the other. Test and adjust until it looks the best you can make it. Some machines have design issues that make a perfect zig zag stitch almost impossible. If you want a perfect stitch and you have one of these older machine, consider getting a better machine.
Now that you understand how your sewing machine tensions work, you can use your sewing machine with renewed confidence. Make the adjustments you need when you need them. Always remember, a trip to the sewing machine shop can relieve stress when all else fails.