Is this happening on the top of your material or underneath. If it's on top it's the bobbin thread. If it's under the material it's the top tension that needs adjusting.

A couple of other things to check--

Is your bobbin seated in the bobbin case right?
Is your bobbin wound evenly?
Is your needle the right size for what you are sewing--Is it bent?
Is the machine threaded right?--Check your manual for these
Are you using a poor quality thread? Good quality thread can make all the difference in how your machine works.

Thanks, oil painter (I am an oil painter, too). It's happening on the bottom. My machine is a Brother and I don't have the manual (90' tree fall on our house last fall and we lost a lot of stuff like that). I'm not sure how to change the tension for the top thread.

All of your other questions are all yes except for the bent needle which is no. I am using a good quality quilting thread.

I will see if I can find where to adjust the top thread tension.

Thank you for all your suggestions.

Sandra

You can get a manual on line. It is always a good thing to have. I keep mine right with my machine.

If I saw a picture of your machine I could probably tell you where the top tension is, but I'm not familiar with the brother machines

Hi, long time lurker, first time poster. :)

I have a Brother machine, the thread tension knob is where the (small) red arrow is pointing, on your machine it may be in a little different place but it should look similar.

Geez, I must be getting old, ghostlyvision! I should have remembered to look there!

Thanks, oilpainter and ghostlyvision, you have saved my day!

Sandra

You're very welcome, happy sewing!

Also, try to clean the inside and get any build up of lint off and a few drops of oil where needed if it hasn't been used for a while. I had (no longer)a old Singer that was acting up. One of the suggestions given to be was to get new bobbins (they were metal) some had some very small nicks that can cause problems. If you have plastic one I would think they wear out much faster than the old style metal ones.