Timing Screw Expertise: Morrison's Nearly 50 Years of Timing Screw Magic 

Great job explaining how the timing screws interacts with product

1:08 - First time I hear "positive control". I wonder why it is called "positive" in positive control. I know what it means from positive locking. Rather I'd like to know why exactly "positive" is used in these names. All I can find are guesses. There are also: "positive displacement pump/meter/pipette".