The Clutch Spring
The clutch spring is held in place by a small collar on the inside end of the clutch rod and a screw bushing on the outside, by which the tension of the spring is regulated. This tension should be sixteen to twenty pounds. A screw pin passes through a slot in the shaft, through the clutch rod, and into the opposite side of the collar. The outer end of the clutch rod is connected to the friction clutch by a screw which passes through the clutch rod. By taking off the clutch and hooking a balance spring in the screw hole in the rod and pulling out on the scale, the instant the rod moves the scale indicates the tension of the spring registered. One end of the clutch rod is connected to the collar on the shaft, and the other end is connected to the clutch. When the collar is moved the clutch rod also moves in the same direction.
When the clutch rod spring is adjusted to a tension of 16 to 20 pounds it gives about the right friction to carry the machine through all its operations where everything is working properly, but if anything sticks or makes the machine run hard, the clutch will slip.