Sewing Machine "bird nesting" Problems?

It sounds like the bobbin tension is out of adjustment. Sometimes you can adjust the tension on the bobbin with a screw on the bobbin itself. Sometimes this is an adjustment that has to be made at a repair shop.

Sounds like it is time to take the machine to the shop for a tune-up.

I concur with @PerryDolia!

Very much time to get it serviced if you’ve been using it for years.

It shouldn’t cost too much to have it overhauled. My Singer guy charges me about $50 for a full cleaning and adjustment, but then I use a 1938 Featherweight that belonged to my grandmother, so parts are a bit harder to find.

The adjustment is simple, but it takes experience to know how far to adjust things.

There are several things that can cause this. Often, the problem lies in the top thread rather than the bobbin thread. Make sure that the presser foot is raised while you’re threading so that the tension disks open up to let the thread slip between. Clean the space between the disks using a little folded piece of paper towel (crud can accumulate in there and wreak havoc with the tension). Make sure that the thread runs under the little spring-wire loop before heading up to the take-up lever (missing this is a common cause of bird-nesting).

Once you’ve done the above, lower the presser foot and check to make sure that the tensioner is doing its job. With the thread out of the needle, set the tensioner to zero tension; tug the thread to see how that feels; then increase the tension bit by bit and verify that it actually is increasing the tension as you dial it in. If all of this is functioning properly, try increasing the top thread tension above where you had it set before, and see if that helps with the nesting.

I assume you know to hold down the tail ends of the top and bobbin threads as you begin a line of stitching. This will prevent the nesting that often happens at the start of a line.

These are the things that would be easy for you to check, but there are several other possibilities that a technician would be better placed to look at.

Good Luck!

Read some of these suggestions which I found by typing “bobbin thread bunching” in my search box. This site with manuals to download might help also.