The machine sews perfectly well for a while, but then it pulls two loops of the upper thread underneath the fabric and breaks the thread. It is always just two loops, and they are exactly the same length - 40 mm. This usually happens with zig-zag sewing, but also occasionally on straight-stitch. I have carefully checked both upper and lower tensions, and the bobbin holder is in good condition - perfectly smooth with no snags.

Geoff, August 2007

Hello Geoff,
Are you using a good mercerised thread, remember that Singer machines were made to take Sylko number 40 and 50 and trylco 60, to use other makes of thread is not a major problem but you will have to watch those tensions, if you have a plastic bobbin case commonly known as an appolo which should be black, if it is grey you have the old style, just check it to make sure there are no burrs on, check those tensions if the problem keeps happening it could well be the machine is out of time.
Ken, e-mail any problems

drivewithken@blueyonder.co.uk, August 2007