The tension of the sewing machine is a very important thing as it affects its performance, to work easily on the sewing machine you must set the tension according to you. Well, before sewing it is very important to check the tension because it can get upset by any small thing.
You may not believe but a damaged or bent needle can also become the cause of unset tension. Moreover, also check if the needle is inserted correctly. The only solution to these problems is to replace the needle or to insert the needle correctly.
Dirt can also become the cause of upset in the tension, make sure you take a quick look for any dirt on the wheels, bobbin, or throat plate. If you find any fluff, you should clean it with the help of a small stiff paintbrush.
The position of the dials should also be checked to ensure that its setting is correct and has not been moved from the regular position. Moreover, the dial setting in most of the machines is 4, you can check your machine's manual to find its best setting.
The quality and weight of the thread used at both bobbin and top thread should be the same. It is because tension problems are also caused when they are mismatched.
The top thread should also be checked to make sure that it did not get caught around the base of the spool. It is because tension issues are also caused because of this, mostly the tension becomes too tight.
Sometimes the sewing machine is not threaded correctly and starts to cause tension issues. In this case, you need to check the threading of the machine and rethread it. Moreover, make sure that the bobbin does not contain any loops and thread has moved through tension disks properly.
These were some of the common problems which mostly becomes the cause of disturbance in tension. It is very important for you to understand the solutions to these problems and fix them, but if you are unable to do that then it would be best to take the machine to an expert.