Removing the Stop Motion Screw

A couple of days ago there was a nice comment from Anonymous saying how much she (or he?) has been enjoying using a Singer 28K, but now there is a problem with the needle mechanism disengaging of its own accord - at least that's how I understood the question.  This is a problem I have had in the past with one of my machines.  The answer was to clean up the stop motion screw and the washer behind it.  

The first step is to take off the stop motion screw - the large silver disc at the centre of the balance wheel.  These photos are of my Singer 201K treadle. With a hand machine you need to unscrew the whole hand crank assembly first to get at the stop motion screw properly.

First, loosen this small screw.  There is no need to take it out completely - in fact, it is better not to. You don't want to wave good bye to it as it disappears down between the floorboards.  Just loosen it so the head is no longer flush in its setting.  Then you can unscrew the stop motion screw itself.

When you take it off you will see the tabbed washer underneath.  If you are lucky, as I was this time, it will remain in place over the end of the shaft.

Usually it comes away with the stop motion screw because it sticks to the inside of it with old oil. Or it just drops away and ends up on the floor.

Once the washer is removed, any mucky residue of oil can be cleaned away from the head of the shaft, the washer and the inside of the stop motion screw.  

It can take two or three attempts to get the washer back on the right way.  The two tabs on the inside of the washer are at an angle. 

 On this photo they are pointing up towards the camera...

... and on this photo they are pointing down towards the table.  Because this is a Singer part it is stamped with the trade name and part number on this side.  This is the side that faces away from the stop motion screw and towards the main body of the machine.

As for the three tabs on the outside, they too have to be in the right position when replacing the washer on the machine.  This post on the Vintage Singer Sewing Machine Blog has an excellent video showing how to make sure it is the right way. 

So, getting back to Anonymous's problem...

Either the stop motion mechanism is sticking because it is gummed up with old oil, dust or sticky old rubbish inside...

...Or the little screw is not screwed in far enough to make the end protrude through to the other side. This end of the screw sits between two outer tabs.  When you turn the stop motion screw clockwise, the washer is pushed that way by the end of the screw, and the needle mechanism engages.  When you turn it anti-clockwise, you turn the washer back in the other direction and disengage the mechanism so you can wind your bobbins with the needle out of action.

So here is the plan of action for Anonymous:-

First check that the head of the small screw is flush with its setting.

If that doesn't cure the problem, take the stop motion screw off and give it a good cleaning. Paraffin should shift ancient sticky muck.  Give the machine a good oiling when you reassemble the part.

Good luck!

Finally, welcome to the latest follower, the enigmatically named me - thank you for following!