Is one end of your machine winning the tug of war? The tension of the upper and lower threads should be the same and just strong enough to lock the stitch.
If the upper thread is lying on the top layer and pulling up the lower bobbin thread the tension is either too tight on the top or too loose on the bottom. Lower the tension on the top (decrease the number on the dial, or remember lefty loosey for some machines (long arm). If that does not work then adjust the bobbin.
If the lower thread lies on the underside of your project with the top thread pulled down with almost a knot like look then the upper tension is too loose. Turn the dial to a higher tension first and if that does not work adjust the bobbin case. To increase the tension remember righty-tighty.
Bobbin cases only need incremental -tiny changes, long arm top tension gauges can take a full quarter turn to change the tension.
Consider the thread you are using and the material you are asking the machine to sew through also. Metallic thread requires a lower tension on the top and with some machines a thread stand. We run metallic on JUKIS on -1 and have no breakage.
Sometimes the thread is too smooth– I love Glide but if it starts sliding out the tension discs too often I go back to my old stand by, Superior Thread.
When I am long arming and the fabric is tightly woven, a batik for example, I use a thinner thread if I am traveling at a higher speed.
When you think of the intricate dance between your batting, thread and fabric it is amazing what these machines are doing. Batting can have an added pull on the thread. Cotton batting hold the fabric well – almost too well and can add a strain the the top thread. Blended battings can come to the rescue for those high speed quilters.
Don’t get too frustrated. Sometimes a simple change of thread, a loosening of the quilt, a check for dust or a re-thread will have you on the way to happy sewing land. A drop of oil in the correct area of the bobbin case/hook area while running the machine without thread or a bobbin and bobbin case and you might be amazed at what will pop out! I have had little lint balls pop out and then I was back in happy sewing land.
Sometimes you have the top threaded correctly but the thread is not in the tension discs. Lower you presser foot and tug the top thread– there should be tension.
A bobbin case does not need that much tension. There is a drop test you can do for your bobbin, I never use it. I sometimes use a TOWA gauge or I just keep the same weight thread in the case and only change the top thread if I am machine quilting on our JUKI QVP.
Some machines are picky– know your machine. I find the JUKIs very similar to the old style, vintage Singers I have at home. I have some other picky machines at home that I would never put metallic in as I don’t want to curse any more than necessary when sewing.
So take your time. Take your manual out on your domestic sewing machine and look at the thread path– are you threading every spot. Did you “dental floss” the thread if your machine doesn’t hold the thread in the tension discs? Is the bobbin in with the thread going counterclockwise in a top loading bobbin? In a front loading or side loading machine when the bobbin goes in the case, the thread should go off the back of the bobbin before placing in the case and then it should go off to the left if you are facing the machine. It is in there clockwise.
Make sure you wind a good bobbin. Bobbin winders have tension adjuster screws. If you bobbin is bottom heavy then increase the tension by turning the screw to the right. If the bobbin is top heavy loosen the set screw.
There are vintage machines that could care less how great your bobbin is wound. Today with all the beautiful decorative stitches and computer boards your bobbin is doing alot more work to make that perfect stitch. Give it some TLC.
Use the correct bobbin for your machine. Paper prewound bobbins can deflate like a pancake inside the bobbin case. I never use them anymore. I want our machines running in tip top shape whether they are vintage Rockateers or spanking new JUKIs. If you have an incorrect bobbin it can move around inside the case, it can be too high and hit or too low and pop. Bobbins are not expensive. Come in or call and we will get you the correct bobbin.
If your machine has not been cleaned and serviced in the last year and you sew frequently you owe it to yourself and your machine to have it cleaned and serviced.
See you soon at Sew Pro. Happy Sewing and Quilting!