Yes, I recommend to buy two such cheap spring dynamometers - typically $3 each. They have saved time for me every time I change thread or fabric, because it is faster to set the tensions right faster with less test sewing. Furthermore a lot of issues can cause the thread tension to vary, and then it can take a lot of test sewing to find the reason. So such problems are solved much faster. For some meachines it is difficult to take out the shuttle to make some verification of bobbin thread tension. With a dynamometer you can measure it right away by pulling up the thread from the needle plate.