I explored some. On this machine the whole face comes off, including bars and lifters, not just the faceplate. I haven't dared taking it off until now, fearing links unlinking and springs springing. It came off in a very civilized manner, no surprises and easy to reassemble.
The first picture shows the thumb screw, the no. 7 on page 9, Macybaby. Then the inside where the screwdriver points to a clamp that the thumb screw connects to. The clamp slides up and down on the presser bar and grips when the thumb screw is tightened. The manual says nothing about the effect or when to use it, only about how to apply more or less.
The third photo is just for fun - serious rust protection behind the face. Somebody took care of this machine, and the recommended lubricant according to the manual was prime sperm oil. And I thought only us Norwegians killed whales. Eeeeh...they are referring to whales, aren't they?
Last edited by steihy; 01-12-2016 at 02:02 PM.