Pfaff 1246 - Manual (Page 54)

Adjustment
11 - 14
11. 04.12 Safety clutch
● Remove the jammed thread.
● Press piston
1 and turn the handwheel until hook 3 of pawl 2 clicks into groove 4.
Fig. 11 - 12
The safety clutch is set by the manufacturer and screws 5 are sealed.
If the thread jams, the safety clutch snaps out to prevent damage to the hook.
A description of how to snap the clutch back in follows.
3
2 1
4
5