Needle Flex and Its Impact on Tension

September 10, 2008

As the weather starts to cool and the leaves turn brilliant shades of red, orange and gold, quilters migrate from their summer gardens back to their sewing machines. The holiday rush begins in earnest, with piecers and quilters alike working under pressure to meet deadlines. As the "quilting season" picks up this time of year, so do the questions we receive about threads and tension!

Many factors can affect thread tension, from fiber content, to quilt tautness, to humidity and even moon phases. Okay, I'm just kidding about the moon phases, but if you've ever struggled with tension, you might think the stars were misaligned a time or two as you tried to quilt! Tension is such a common question that I'm planning several articles and videos for you, to help you figure out how to make adjustments to your tension so that your machine sings!

This first article focuses on a little-known aspect of tension and stitch quality called "needle flex." If you machine quilted on a domestic machine before you started on a long arm, think back to how you moved the fabric. Do you think you could move the fabric as fast as you can move your long arm machine and still have a decent pattern? Probably not. You can move your longarm machine much faster, which has a huge impact on the needle. That's why your longarm needle is so large--it is to reduce the impact of needle flex!

As you move the machine in different directions, the needle drags in the opposite direction you move. For example, if you move the machine to the right, the needle flexes to the left, and vice versa. Now think about the hook assembly for a moment (for the uninitiated, that's the part of the machine where the bobbin case sits). The hook's point rotates around the bobbin, pulls the top thread around and locks with the bobbin thread, but the entire hook assembly itself does NOT move.

So, for you to get the best possible stitch, the hook point and needle must meet at "just the right spot" during that rotation...in "perfect time"! If the needle flexes and gets there too late, or flexes away from the hook and leaves a gap, your stitch quality and tension are impacted. Think back to the Summer Olympics and those fantastic gymnasts on the uneven and high bars. Do you remember watching those bars bend as the athletes put force on them? (Think needle flex.) Did you see what happened if the athlete's rotation was a bit off when it was "time" to grab the bar again? Yes, they landed on the ground...ouch! (For quilters, if the needle flexes too much, we get "tension headaches!")

APQS machines are tightly "timed" to give you a terrific stitch. But needle flex is a variable that you must consider when you quilt. These things will increase needle flex, and consequently affect your tension (resulting in pokeys on the back during directional stitching):

• Quick movements, both with and without a stitch regulator;
• Long stitch lengths;
• Tightly woven fabric such as batik or high thread count muslin;
• Taut fabric between the rollers;
• Extra tight side clamps;
• Heavy or strong thread, such as thicker cotton (King Tut, for example)
• Needle too small for chosen thread, batting or fabric.

To reduce needle flex:

• Quilt at a steady pace;
• Set stitch length to 10 or more stitches per inch;
• Reduce the roller pressure on quilt sandwiches, especially with tightly woven fabric;
• Relax the pressure on side clamps;
• Use a larger needle with coarse, thick, or heavy thread;
• Use a larger needle with dense batting or a thick quilt sandwich.

Finally, the direction you quilt will make a difference in your stitches, due to needle flex. Have you ever noticed that your stitch quality changes when you quilt to the left when standing on the freehand side of the machine, or when you push the machine away from you? Quilting to the left pulls the needle to the right, and it gets to the "timing spot" too late to meet the hook. As you push the machine away from you, the needle flexes away from the hook as well, creating a little air gap.