Brother b831 Service Manual page 41

7. The path of the thread wiper O tip is shown in the figure above.
The needle tip to thread wiper O tip gap should be 0.5 to 1.0 mm. Loosen screw O to adjust.
ffl Step 3
If the 0.3 mm gap is too great, the thread wiper O will strike the presser foot.
If the gap is too small, thread wiping will not be properly performed.
Bi Step 6
If the 1 mm gap is too great, the thread wiper O will strike the presser foot,
ffl Step 7, above
If the 0.5 to 1 mm gap is too great, thread wiping will not be properly performed.
If the gap is too small, the thread wiper O will strike the needle tip.
- 3 8 -
Needle
0.5~1 mm