Pfaff 3119 Instruction Manual page 28

Setting up
9 Threading the bobbin case / adjusting the bobbin thread tension
.03
For purl buttonholes:
For flat buttonholes:
9 - 3
2
1
5
7
6
Fig. 9 - 03
Insert the bobbin 1 in the bobbin case.
First guide the thread into slot 3 and under spring 4.
Then guide the thread into slot 5.
Push thread through opening 6.
Push thread through opening 7.
Trim thread on thread knife 8.
Adjust the thread tension by turning screw 9.
To do so use the tools supplied.
When sewing flat buttonholes, the tension of the bobbin thread must be so
high, that the bobbin thread is interlooped on the bottom side of the material.
3 4
8
9