Singer Rocketeer Bobbin Winder Spring

One of the weak points of the Singer 500a and 503a is the bobbin winder spring.  The spring breaks and the bobbin winder will no longer spring back when the bobbin is filled.  Sometimes, the bobbin winder won't even latch to fill a bobbin.

Fortunately, I had a good spring to use as an example, so I wasn't "flying blind".

Measurements are quite simple and only one is critical - the straight arm of the spring is 3/4" long; the L-shaped arm has a 3/4" long extension, then bends down at a 90-degree angle for another 3/4".  There is only one coil.

For the price of one ready-made spring on the internet, I purchased a 446-foot coil of .029" diameter spring wire. I think I will have enough wire to fashion my own springs for several lifetimes.

I cut off about a foot of wire so that I would have enough to grab onto and wound it around a bolt.  I like to use a bolt because the threads help keep the coils even and straight.

 Then, I cut one arm off at 3/4" and the other at 1 1/2".  I put a 90-degree bend in the long arm and was ready to install.

Unfortunately, I made the coil too small.  This is when I learned that the critical measurement is the coil section - it has to be approximately 1/2" in diameter.

 Larger diameter might work, but I made the first spring with a smaller coil and the bobbin winder mounting screw tightened against the spring and would not allow the bobbin winder to swivel.  It seems counter-intuitive to me, but the coil of the spring must be large enough to remain outside the bobbin winder's swivel arm.

Several more prototypes with unsatisfactory coils.

I finally found a dowel that allowed me to make the correct 1/2" coil and got a good copy of the sample spring.

 If I were going to make many more, I would pick up a larger diameter bolt to wrap the wire around but I only need two right now, so the dowel will suffice.