I know Jamie Wallen has a video on taming tension that is real good

Jamie Wallen. https://youtu.be/Q1mRhcquZTM?t=128

I have the video set to start right at where he explains the test, but it's well worth your time to go back to the very beginning of the video and watch the whole thing.

I have a Handiquilter Sweet Sixteen. I use a lot of different threads, including 100 wt. poly and 100 wt. silk, even some 12 wt. cotton, as well as a lot of 40 wt. Isacord and Glide. I have several different bobbin cases- one for very fine threads, one for the 40 wt. threads and one for the thick threads (12 wt.). Even so, I test my bobbin tension with every thread and adjust accordingly. I have never used a Towa gauge, though I've been tempted to buy one, but usually I'm happy with my tension if I test it by laying the bobbin case flat in my hand with the open side down, and lifting on the thread. If the tension is right, I can pull on the thread to raise the bobbin case up so it is standing in my hand, but it doesn't come out of my hand. In this position, if the thread pulls easily and smoothly from the case without changing the orientation of the case and without lifting it out of my hand then I'm usually good to go.

Once I've adjusted my bobbin case so that the tension test works as described above, then I fine tune it by adjusting the top tension. I do this every time I load a new bobbin, even if I haven't changed the type of thread. I also check the tension on a scrap sandwich whenever I start a new bobbin, or if I've been away from quilting for a day or two. Works well for me. I think that's also the test that Jamie Wallen uses.

I hope that makes sense.

Rob

I use Jamie Wallen's method too. There may be times when you want a bit tighter or looser tension for the bobbin. But golly, that method sure gets me good to go for the most part! I am think maybe for stuff like thread painting if you want to do that on your long arm, you want a bit more tension on the bobbin so the top thread pulls a tad further into the batting so no bobbin thread shows ever, just like on an embroidery machine.

I have one and I use it ALL the time.

Right off the top, I am not sure the "plain" Towa and the electronic Towa give equally reliable results. I found the electronic version completely unreliable. I have never tried the non-electronic version of the gauge.

So far, knock on wood, the drop test has worked well for me. Like Suz, I find it helps to just ever so slightly over tighten.

As for bobbins, I bought the Glide magnetic bobbins when I first loaded my longarm, and thought the machine was broken as I could not fix tension issues. Turned out the magnetic bobbins are sometimes over-magnetized and create way too much drag, or high bobbin tension. I have never used the things since.