Quilting is fun and easy! Really, it's getting your tension right that is hard.... really, really hard! I use the HandiQuilter Avante at TechShop and this is my method for getting the tension perfect for each quilt no matter what thread, fabric or batting I am using.
Step 1: Tension Testing Sandwich
If you've been using a longarm for awhile, you have probably had a small scrap of batting and fabric off to the side of your quilt using the excess in your quilt backing. As you make adjustments to your tension you bend under the machine and try and see how it looks. Or, you try and fold the fabric right side up, stretching your back and altering the overall fabric tension. It is a pain and isn't always successful. But there is a better way!
When you purchase your quilt fabric backing and batting make sure you have an extra 12" x WOF (Width of Fabric, usually 44") that you can sacrifice to the longarm. You will create a quilt sandwich that is 12" wide x approximately 44" long. In the pictures included I used the same fabric for the quilt top and backing to
Step 2: Belly Up to the Bar
Take your new quilt sandwich to your longarm and attach it with pins to the bar in the back. Next, bring the sandwich forward and lay it over the belly bar. This is the forward most bar you'd touch with your belly if you were leaning against the machine. Now you will belly up to the bar to hold that piece in place while you use it to do your test stitches.
Step 3: Bobbin Tension by the Numbers
There is a great little device called a TOWA Bobbin Case Tension Gauge. It allows you to measure the tension on the thread in your bobbin case, removing some of the guess work from getting your tension correct. Also, your bobbin doesn't have to be full to measure the tension which is great when you use a shared machine, like I do at TechShop. I might stop a project without being finished and someone else will adjust the tension before I come back to the project. This tool allows me to pick up where I left off with balanced tension.
To use we will load a bobbin into the bobbin case and click it into the TOWA. You will then pull the thread through the wheels as shown.
Step 4: Using the TOWA
Pull on your thread to the left and you will see the gauge will move giving you a range of the tension on the thread. Each machine and thread is different so the number you will target will vary. I have kept a record over time for my preferences. In this case, I am using So Fine #50 from Superior Threads and I prefer the bobbin tension to range from 110-130. Since the initial bobbin tension is measuring below 100 I need to adjust it.
I use a small eyeglass screwdriver and turn the bobbin tension adjustment screw about 1/8 of a turn and test again. As you can see from the picture, that was enough to bring the tension into my target range. Bobbin tension adjustment is very slight for big results.
Step 5: Threading the Machine
There are two things I do differently to ensure a good tension.
1. Only run the thread through the top hole of the three hole thread guide. I find this creates less tension there and lets me control it more precisely with the tension disc.
2. Wrap your thread completely around the tension assembly. Normally you would wrap it under and then up thru the spring. By making a complete circle around and then coming up thru the spring your thread won't jump out of the tension discs, causing all kinds of havoc on your quilt back.
Step 6: Quilt!
Belly up to the bar, bring the machine over your quilt sandwich and run some test stitches. Make sure you make plenty of circular patterns as they show problems with your tension the most.
Back off the belly bar and lift your fabric. (Make sure the machine is not active and you've cut your threads!)
I have used white thread in the top and black in the bottom to make it easy to see problems. When looking at the top it looks ok, although a bit loose. After flipping to the bottom it is clear to see the white thread poking thru which indicates the top tension is too loose.
Step 7: Adjust Your Top Tension
Turn the dial for your top tension disc about 1/2 a turn away from you to tighten. (If you had to loosen you'd turn towards you.) This is a reasonable adjustment for each test until you get it just right.
Step 8: Quilt! Again...
Now that we've tightened the tension disc 1/2 a turn you can see that the tension is quite a bit closer to balance with fewer white threads poking through the bottom.
Turn the tension disc again and test again. The final image shows a nice balanced tension and I made it at TechShop!