Underthread Going Crazy
Hi PixelPup....Although I am unaware of what types of fabrics/needle size/project (ie does it have batting or metallic/special threads) your issue involves a fault located above your needle plate with 2 points of interest in particular.
1) Appropriate Needle Size, Type and Insertion.
2) Absence of upper tension.
When replacing needles, ensure that the groove along the length of the needle is facing you. For every day medium weight cottons, a universal size 70 or 80 needle is fine. However, ALL OTHER fabrics, especially knits, denims, stretch and very lightweight or sheer fabrics should be sewn with the specified needle types. Your local sewing retailer can help you with exactness if you bring along a swatch/sample when you shop for your needles. Please purchase your sewing machine supplies from a sewing oriented retailer. Needles AND Thread quality matter a great deal in the quality and longevity of your stitches. As for needles, I recommend Schmetz, and Viking for threads. Keep in mind that needles to get dull, and can easily acquire brays which may not only cut your thread, but damage your fabrics as well, and should be changed "regularly".
I would guess that misthreading accounts for 95% of all sewing machine problems including lockups, needle breakage, and instant jams. The dial for your upper tension may have a "colored zone" for the universal tensioning starting point usually between 3.5 & 5.5, with the lower number for lighter fabrics, and increasing with weight. If you don't have a colored zone, begin with #4. Completely remove the thread spool from your machine. Ensure that your presser foot is in the up position, and begin methodically threading your machine, paying special attention when you reach the tension area. There are usually 3 or 4 'plates' that provide the tension, and rushed threading by experts regularly causes the thread to miss the discs altogether. The presser foot must be in the raised position, which releases the pressure on the tension discs enabling your thread to slide in. Why not be proactive and remove and rethread your bobbin as well, ensuring that your bobbin thread receives tension from the flat spring on your bobbin case.
Unless I have misunderstood your issue, your problems should now be solved......good luck my friend.
on Feb 03, 2015