This could be one of the following:
- wrong bobbin for the machine
- bobbin loaded the wrong way - must rotate anticlockwise when you pull the thread
- thread not into the tension spring/device on the bobbin holder correctly
- bobbin wound badly, uneven tension, loose or uneven across the bobbin
- poor quality or old dry brittle thread could cause the breaking (but the loops is definitely tension issues).
This is a top loading bobbin machine machine and you can download a manual from
http://www.singerco.com/accessories/manuals.html
Here is the threading diagram from the manual.
It is important to click the thread down into the tension spring on all top loading bobbin machines and then pull gently on the thread to check that it is under tension, you should feel firm resistance when you pull the thread. If not, then take it out, and try again.
Other thing to look at is how the bobbin is wound. It is necessary to wind a bobbin smoothly and with some tension on the spool as the thread comes off it. Best analogy is the garden hose reel. If you wind it up and don't control where the hose goes onto the reel it will all lump up in the middle, and you won't get all the hose onto it. And then when you go to pull the hose out, it will jam and be difficult to pull. Same with bobbin thread. You want a nice neat even fill across the whole width of the bobbin, not just the middle. To achieve this make sure you use the bobbin winder tension disc when winding. Also use the spool cap on top of the thread spool to stop it from bouncing around as it unwinds - the thread will then wind off around the spool cap and this keeps it running smoothly and not twisting and jerking. If you don't have a spool cap then put the curved handle of a pair of scissors on top of the thread spool to tension it while you wind the bobbin. Also watch the bobbin as it winds, give the thread a nudge with your finger to control the fill onto the bobbin so it winds top, bottom and middle of the bobbin evenly.
I would suggest the following:
clean out the race following the manual directions to remove the bobbin holder, clean in this area, replace it. Wind a fresh bobbin and then load it into the machine, following the manual instructions carefully. Also thread the top of the machine following the manual, put in a new sharp needle from the pack, turn the top tension dial to a medium number (often 5 if dial goes from zero to 10).
Now test sew again. Look at the seam, if you have loops on the bottom of the fabric, underside, then the top thread tension is too loose or not in the top tension discs fully. Generally you should not need to adjust the tension on the bobbin thread for these machines.
