sewing machine thread tension?

Question

On a sewing machine how do you set the thread tension on the bobbin and needle?

Answer 1

"Normal" top tension setting when you get it back from cleaning is 4. If you have to change the tension settings to get a good stitch, it shouldn't be extremely far from 4, especially toward the "greater tension" settings. If that happens, it's probably time to floss out the top tension with a piece of folded, washed muslin
moistened with rubbing alcohol or unflavored vodka. Chances are there's either some yuck built up from thread coatings or fast sewing, or fluff from not so wonderful thread, or a piece of thread in the tension. Or you've mis-threaded.

What you're looking for (for almost all purposes) is a "balanced stitch", which, if you could see through a cross-section of fabric would look like this:
http://www.westsidesewing.com/wss/tips/art_pt02.pdf
This is a pretty good discussion of setting tension, and some of the other factors (besides tension issues) that can cause "tension problems".

If someone's been messing with the bobbin tension (and I do it a fair amount on my grandmother's old machine, because it's the one with an easy bobbin case and it doesn't mind elastic thread and other heavy threads in the bobbin), start by setting the top tension to "4", putting in a size 80/12 sharp or universal needle, and finding some muslin or similar cotton cloth. Thread up top and bobbin with good thread, preferably white or pastel, as dyeing can do some interesting things to some threads-- wiind the bobbin from the same spool as the top thread.

Load the bobbin case and pull out about a 6" thread tail. Hang on to the end of the thread and drop the bobbin case. If it descends rapidly toward the floor, it's too loose. Tighten the screw and try again. When it's just at the point that it'll hold its own weight but pay out about 1/4" for every time it gets "tick-tocked" back and forth, it's about right. If it won't let go of any thread, loosen it a bit.

Bobbin screw adjustments are touchy, so 1/4 turn is a BIG adjustment. 1/8-1/10 turns are more likely when you're at the fine-tuning end of things.

When you think you're close, put the bobbin case in the machine and sew some test seams on doubled cotton muslin. Inspect for balance. If you're getting good seams with the upper tension setting someplace between 3 and 5, I probably wouldn't mess further with the bobbin tension screw. If it's well out of that range to get good stitching, adjust the bobbin case a smidge and try again.

More good info:
http://www.ca.uky.edu/hes/fcs/FACTSHTS/CT-MMB-213.pdf

Answer 2

the "new" machine manuals don't tell you anything about setting the tension except for adjusting the top tension. The old machine manuals always showed what a proper stitch looked like and how to change it. The numbers are just to give you a reference, in fact the old machines didn't even have numbers on them. The point is that the stitch should interlock between the layers of fabric. One way of testing the proper tension is to stitch a length on a bias, then pull the ends of the fabric sharply until the threads break. They should break both in the top & bottom. If the top thread breaks, the top tension is too tight (or the bobbin too loose). If the bottom breaks, the bobbin tension is too tight (or the top is too loose.) The arbitrary 5 is a good number for the top since you can adjust it up or down from there easily. You have to be cautious about adjusting the bobbin tension; only change it an eighth or quarter turn at most. Test, then adjust if necessary. If you aren't careful you can also lose that tiny screw. Doing it over a magnetic pin tray is a good idea.
I imagine manufacturers quit telling people about adjusting the bobbin to prevent them from going overboard or just make it sound simpler. You don't want the tension so tight that you can't pull it thru without breaking. In my Bernina club we were taught to adjust the bobbin tension by loading the bobbin case then dangling it by the thread. A small jerk should allow the bobbin case to drop. You might have to readjust your tension depending on the type of fabric you're working on. Make some test samples first.

Answer 3

Don't touch the bobbin tension. They don't give you a way to tell how far you turned it or how to get it back.

The top tension will have a knob with numbers according to the type of project you're working on. It's best to use the manual because every make and model of machine is different. It won't work properly if the machine isn't tuned once a year.
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Answer 4

Tension Setting

Answer 5

What grichter said.....
Adjusting the bobbin tension is a last resort for anyone not totally comfortable and familiar with their machine, but it can be done easily.
One additional comment though. Always change the top tension adjustment with the presser foot UP.