A Discussion on Tension
Here is what I understand about tension. First of all, it is a tug of war. If you remember as a child playing tug of war the goal was to pull harder than the other team to get the center flag onto your side of the field. In achieving good tension on the sewing machine we want the tensions to be equal and that “flag” to stay in the center. There is no magical number for the tensions, but keeping the tensions equal is the goal. For this reason I always teach adjusting the bobbin tension first, then adjusting the needle tension to match that. I like my bobbin tension fairly loose. By that I mean when laying the bobbin case in the palm of your hand you are able to lift the bobbin case up onto its side holding the thread that is placed in the tension strap, but not in the “piggy tail.” (The piggy tail is the little spiral shaped wire on the front of the bobbin case. I place the thread in the piggy tail when I have finished adjusting the bobbin tension.) As you pull your hand away from the bobbin case it should gently fall with your hand. There should be tension felt, but it should drop gently, not like a rock. If the bobbin case does not move or has to be shaken down it is much more difficult to achieve a balanced tension. If the bobbin case does not drop, turn the tension adjustment screw (the large screw) left 3 to 5 minutes as on a clock. If is drops like a rock, turn the tension adjustment screw right 3 to 5 minutes and try the test again. Test the tension by sewing a figure 8. Examine the result. Has the stitch locked inside your project? Yay! You got it. Can you see the bobbin thread peeking out on top? If so, then loosen the needle tension by turning the adjustment knob counter clockwise. The needle tension is MUCH less sensitive than the bobbin tension strap. Turn the tension adjustment knob AT LEAST one full turn when making adjustments. Can you see the needle thread peeking out underneath the project? If so, then tighten the needle tension by turning the adjustment knob clockwise at least a full turn. Pay no attention to the numbers on the knob. Use them to know if your turned a full or half turn. ALWAYS MAKE SURE THAT THE NEEDLE THREAD IS FLOSSED INTO THE TENSION DISCS. The thread may appear to be in the discs when in reality it is only resting on the edge of them. Please note that the thread may be hampered by lint from moving smoothly. Take a business card and slip it under the tension strap to clear any possible culprits from under it. Use a brush to clean inside the tension discs that the needle thread runs through. There are many elements that effect tensions.
- Thread weight and drag. Weight is indicated by # and a number or WT and a number. #40 to #60 (40 WT to 60 WT) are common weights used in quilting. The higher the number, the finer the thread. To add to the confusion there is another measurement of thread called TEX. This measurement is the opposite. You will see it on the label as TEX and a number like TEX 30. The higher the number, the heavier is the thread. TEX 30 is close to #40. This method of measurement is less common. I prefer using a three ply thread. Stay away from the serger threads because they aren’t as strong as they need to be for quilting.
- You should be using equal or less weight and drag in your bobbin than is in the needle.
- Drag is caused from thickness of thread or loose fibers. When cotton thread is created fibers are twisted together leaving small ends. That is why people sing the praises of Long Egyptian cotton because the fibers are longer and leave fewer ends. These ends drag on the tension disc and strap and increase the tension. There is nothing wrong with this, but you need to be aware of what is happening and that you need to loosen the tension.
- Polyester thread is one continuous fiber, often twisted over a core of polyester. It has less drag because of the lack of loose ends. A wonderful combination is Cotton like King Tut in the needle and a nice polyester like PeraCore in the bobbin. Having less drag in the bobbin makes it easier to get better tension.
- There are other threads that are REALLY slippery. An example are the trilobal threads that are polyester, but the fibers have been forced through something like a sieve to create three sides. Three fibers are twisted together to make these threads shine. They are very slippery and have very little drag. You need to tighten the tensions on these.
- Another element influencing tension is batting. The thicker the batting, the easier it is to get the stitch to lock inside the project. If the project is thicker there is more wiggle room for the stitch to lock.
- 100% cotton batting is among the thinnest battings and requires a little more adjustments to get great tensions.
- High loft polyester is among the thickest and easiest to achieve perfect tension.
- I love the 60/40 blends. That is 60% cotton and 40% polyester. It has the finished look of cotton, but is easier to get the adjustments on tension because it is a bit thicker.
- Fabric density also effects tensions.
- Think of the difference of Home Spun or flannel type fabric as opposed to 800 count sheets. The fibers are more densely woven in the sheets making is harder for the needle to pull the thread through the fabric. Try to match your quilt top and quit backing to be the same type of fabric so you aren’t battling the loose weave/tight weave battle.
- Painted fabric also requires the needle thread to pull harder to get the threads to lock. An example of painted fabric is batik.
- None of these are “bad” fabrics. It is just important to know what adjustments need to be made to be successful.
There are some mechanical items to notice to make sure all is in proper order with your machine. There is a check spring attached to your tension unit where the needle thread runs through. It is important that the thread is in this check spring. Its job is to lock the stitch by pulling on the thread. Notice that when you pull on the needle thread near the needle the check spring will move. If it is not moving, check to make sure the tread is running through the check spring. Also check to make sure that the check spring is positioned at about 11 o’clock. If it is not in the correct position, you will be able to adjust it slightly by using a screw driver in the center screw of the tension unit and turning it in the direction that is needs to move.