Pfaff 3811-2/45 Instruction Manual page 14

Screw 3 (fig. 1)
+ = more tension
- = less tension
Milled ring 4 (milled nut 5)
+ = more tension
- = less tension
Adjusting lever 6 (fig. 3)
14
The pressure from the top feed 1 (fig. 2) and that of the presser foot should
be adjusted so that the workpiece is fed perfectly at all sewing speeds.