Do you have to hold the bobbin winder down in order to get it to wind? If so, then the washers around the bobbin winder screw either need replaced or turned around. Follow the video tutorial or step-by-step photo tutorial below to learn a few simple tips for servicing your Singer Featherweight Bobbin Winder.
The cupped washer keeps consistent pressure on the bobbin winder arm, resulting in pressure from the bobbin winder wheel onto the Singer Featherweight belt.
The cupped washer goes on the screw with the concave (cupped side) of the washer facing away from the screw head.
Also, the bobbin winder wheel should spin freely. If it does not spin freely and additional pressure is the only solution to winding even bobbins, then here is a test.
Put a loaded bobbin onto the winder. Attach the bobbin case tension meter clip to the end of the thread and pull up. It should have very little tension - no more than about 5 grams.
If the bobbin spins on the bobbin winder with difficulty and the tension reads too high, then this extra resistance will cause the bobbin winder wheel to slip, not making complete and smooth contact with the belt.
In this case, most likely there is nothing wrong with the winder, it just needs a little oiling for the wheel to rotate smoothly again.
The bobbin winder arm has a little oiling hole, and it needs just one drop of sewing machine oil. If the wheel is really stiff, try a drop of kerosene first, spin it for a little bit and then once it is spinning freely, follow-up with the one drop of sewing machine oil.