Brother BAS-311H Service Manual page 68

7. ASSEMBLY
Align the needle bar (19) so that reference line A (the second lowest
reference line on the needle bar (19)) or reference line a (top
reference line) is aligned with the lower edge of the needle bar bush
when the machine pulley is turned to raise the needle bar (19) from
its lowest position, and then set the cut section so that it is facing
forward and tighten the screw.
4647Q
59
Inside hole
Cut section
BAS-311H
18. Needle bar clamp
19. Needle bar (Insert from above)
20. Screw
21. Rubber cap
3340B
Needle bar bush