Pfaff 1425 Instruction Manual page 52

Adjustment
11 - 16
Press key 3, Fig. 7.02 (diode on).
Set vibrating presser 14 at t.d.c. by turning the balance wheel.
Turn screw 3 downwards until a clearance of 7 mm is reached between vibrating
presser 14 and the needle plate.
Screw nut 4 up to the housing and lock it with nut 5.
Screw on spring plate 1 (screw 2).
Turn screw 3 downwards until a clearance of 5 mm is reached between vibrating
presser 14 and the needle plate (Requirement 2).