Originally Posted by Irvin
Turning the screw in either direction doe not open or close the gripper. If you screen it in the end of the screw hits the plates sooner and limits the travel so the gripper will not close as far. If you screw it out the gripper travels farther. The farther is travels when tension is pulled the more it closes down on the string.
This. The adjustment screw on crank machines doesn't open or close the gripper as it seems that it does. At least it didn't on the two I had.