The Rotating Hook Lockstitch

Unlike the oscillating hook this system requires two complete revolutions for each stitch. The motion is continuous, quiet and smooth. Again, the thread is moved around the bobbin.
The Parts
The bobbin is stationary apart from a small rotary movement caused by the unwinding of its thread (purple). The hook rotates toward the operator to catch the top thread (red) which is pulled out and around the bobbin. The tail of the hook is shaped so that the part of the loop at the back moves forward to twist the loop. This makes a more secure stitch. As the hook progresses it gets to a point where the loop can slip off. The take up lever then takes in the slack to trap the thread from the bobbin whilst the hook makes another turn. There is no loop to catch during this second turn. The whole process is very smooth and quiet.
A twisted Lockstitch using a Rotating Hook
I used a Singer Featherweight (222K) as a model for the animation. The hook is actually a complex shape and very carefully engineered. A similar system is used on the early Wheeler and Wilson machines. There is an example on the machines page of this site.
The complete stitch