Hello Jan,
Use WD40 which is a very fine oil, take the bottom off the machine and oil all moving parts, unscrew the faceplate and oil moving parts, you can undo the screw on the back of the machine and prise the body apart but it can be tricky, there are catches on the inside but if you are careful they will open. not to sure what you mean by bobbin won't release cotton, do you mean bobbin winder or bobbin case? e-mail me, ifyou have Singer shops in France you are very lucky, they do not exist in the UY any more.
Ken
drivewithken@blueyonder.co.uk
August 2008
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