Singer 28 bobbin winder spring
 

I am restoring a 1908 Singer 28K and all is now working well apart from one part. The bobbin winder has a Spring action arm with a small pull knob that holds the bobbin in place. This is the arm at the top left opposite the cupped end above the cam. My problem is the Spring is weak/broken and will not hold the bobbin in place for winding without pushing on the end though out winding.
It is not obvious how to access the Spring. Is the knob screwed or pressed onto the shaft? I guess any small Spring of the right length could be used as a replacement but I need to get to the old one first!
Any help with this would be much appreciated.

There might be a grub screw some where, or it's threaded. It might be a two piece bolt like thing with a spring too. I think it should come appart. I haven't done a full disassebly of a long bobbin winder myself unfortunately. If you aren't completely sure the spring is broken and the trouble might cause by sticky grime you can try spray can oil. There probably are replacement springs for these. Some make their own by bending and winding a suitable wire into shape by hand, the tricky part is to track down the correct type of metal wire.

If you don't get anywhere contact Helen Howes, she has parts and knows the 28 very well. In the worst of case you can identify the correct winder (there are a few variants on the 28K), Helen Howes has complete winders listed on her site (she has even more in storage) and there are usually some on ebay too. She might have the spring.

Thanks for your suggestions. I'm pretty sure there isn't a grub screw. I can't tell if it's threaded or a tight push fit. I saw somewhere that the knob can just be forced off and re-attached with a vice but I'm not convinced this is the right approach. I'll try approaching Helen Howes.