Unjamming a Stitch Length Regulator

It can be frustrating doing up an old machine when something is seriously jammed.  This is the stitch length regulator on a Singer 99K hand machine that I have been working on.  When I bought it earlier this week the knob was screwed all the way in and stuck fast.  It was stuck in the position for the longest possible stitch.    

It wasn't possible to get any oil in and onto the thread of the screw, so for two nights running I laid the machine on its back with a piece of cotton yarn wrapped around the screw and soaked the yarn with oil.  The hope was that oil would seep down into the machine and start loosening the screw.  No joy.  Even when using locking adjustable pliers, with a strip of leather protecting the milling around the knob and to help grip, it just wouldn't budge.

It was time for a different approach.  The most likely cause of the jam was hardened residue left by old oil.  This can be softened with heat, so I gave the machine a good blast with a hair dryer until the knob was hot.  I was a little worried about applying too much heat and affecting the japanning, so if I ever need to do this again on another machine I will make a cardboard collar to protect the rest of the machine.

While the knob was still warm I tried turning it with the pliers, and finally it moved.  Sure enough, when I could see the thread of the screw, there was the black residue that had caused the trouble.

The quickest way to get rid of the residue is with metal polish.  I always have a tube of Peek metal polish handy to use on my sewing machines, so I put a small splodge onto the screw.

Then I used some strong crochet cotton to rub the polish back and forth into the grooves of the thread.  The muck came off quickly and easily.

Because there was bound to be some more rubbish left inside the machine, I oiled the thread, screwed the knob back in, cleaned that oil off (which came out brownish), and repeated a couple more times until the oil came out clean.   

Now the knob is nice and clean, and easily adjustable, so once I get the machine up and running I know I can adjust the stitch.

I am now over halfway through cleaning up this particular machine and should be ready to test the stitch in a couple of days.  It is a while since I worked on a machine.  I had forgotten how much I enjoyed it!