Bobbin basics

July 19, 2013

bobbinsThe poor bobbin has earned an undeserved reputation as mysterious and misunderstood. Countless sewing machine instructors have instilled fear into the hearts of new sewers, advising them to never touch the bobbin tension. What, pray tell, would happen if you actually did?

Well, for one thing, you might discover the key to balancing your tension and having beautiful stitches! We hereby grant you permission to change the bobbin tension and promise that the quilt police will not arrive with handcuffs to arrest you.

Longarm quilting machines require much less bobbin tension than you may believe when compared to your home sewing machine. Your top thread must travel a great distance around your bobbin before it pulls up the bobbin thread. If the bobbin tension is too tight, it can lead to:

  • top thread pokeys on the back – little dots of top thread appear on the back of the quilt
  • railroad tracks – areas where the bobbin thread seems to just lay on the surface of the quilt back
  • top thread breakage, particularly with cotton thread or fragile threads

You can use a Towa gauge to help you determine tension, but it will only serve as a guide. Each quilt will present different circumstances which can require adjustment, including the batting composition and thickness, fabric condition, thread type, machine speed, stitch length and your personal motion.

Needle flex is the biggest single factor affecting balanced tension. The more it flexes, the harder it will be to keep consistent stitch quality. When the top and bobbin tension are tight, the thread pulls hard on the needle and increases the flexing motion. You can run the machine with looser top and bobbin tension and still have beautiful stitches, since the looser tension will allow the top thread the opportunity to do its job and pull up the bobbin thread. It’s ok if your bobbin case drops to the floor when you lift the thread tail if it gives you good tension!

Spend time evaluating your bobbin case. Clean out any lint or thread from underneath the tension finger along the outside of the bobbin case. Remove the bobbin brake spring occasionally and clean the interior portion of the case.When your bobbin rests in the case on top of the brake spring,the bobbin should protrude slightly above the rim of the case. This tells you that the brake springs “fingers” are applying pressure to the bobbin when it’s inserted into the hook assembly, and that the brake spring will stop the bobbin from spinning when you change directions.