Whether you are sewing, quilting, or embroidering one of the most important things to consider is your machine's tension. Every sewing machine will have an upper and lower tension. While the machine comes from the factory with its tensions set at standard you may need to change them depending on what type of thread, fabric, or stitch you are using.
Most upper tension units are simply two disks pushing together to create tension as the thread travels through the machine. So when should you change your upper tension?
When your upper thread tension is too low:
If your upper tension is too low that can cause large loops on the bottom side of your fabric.
Before changing your tension you should try rethreading the machine because there is a chance the presser foot was left down when you went to thread the machine and if the tension disks are already closed it will seem like there is no tension.
When your upper thread tension is too high:
If your upper thread tension is too high that can cause thread to pucker the fabric, break thread, and needles to bend and break.
Ideally you want your upper and lower thread tensions to be as low as possible and still look good.
As the needle thread is pulled around the bobbin case, it wraps around the bobbin thread and pulls it up through the needle plate. Bobbin Cases come in many different styles and using the right one for the right situation is important. Bobbin Cases are also known as Inner Rotary Hooks. This section will mainly focus on Baby Lock machines.
Baby Lock Bobbin Cases:
Front loading machines like the BL9 and Zest take Part # J01313Z3 ($7.99)
Green Dot Bobbin Case: The Green Dot Bobbin Case is the standard bobbin case for most top loading Baby Lock Sewing Machines. Note that the tension (green colored screw) is not meant to be adjusted; its factory set for standard sewing. If you adjust the screw, you may permanently damage your bobbin case. You may use the Green Dot Bobbin Case for embroidery only when using 60wt Finishing Touch Bobbin Thread. Part # XE5342101 ($23.99)
Purple Dot Bobbin Case: The embroidery case with no color on the screw is set with a tighter tension for embroidering with different weights of bobbin thread and various embroidery techniques. Pre-wound bobbins would be an example of when to use this. The screw is not covered so you can adjust it yourself. Lefty loosey righty tighty. Part # XC8167651 ($28.95)
Red Dot Bobbin Case: The Red Dot Bobbin Cases are included with embroidery only machines and are meant to be used with 90wt Finishing Touch Bobbin Thread. The screw is also exposed to allow for tension to be adjusted. Machines include The Flourish II, Meridian, Pathfinder, Spirit. Part # XF5790101 ($28.95)
The trick to getting perfect embroidery tension is a combination of a few things. As stated above, using the right weight of bobbin thread with the correct bobbin case is key. Using a high quality top thread that is meant for embroidery such as Robison-Anton Poly ($5.99). Old thread weakens over time and becomes brittle and will shred while in use.
You will want to hoop your fabric tightly to avoid flagging (The up and down motion of the material with the needle that is caused by improper hooping). The ideal tension for embroidery is 1⁄3 top thread, 1⁄3 bobbin thread, and 1⁄3 top thread.