4-14.Adjusting The Loop Stroke - Brother RH-981A Service Manual

4-14. Adjusting the loop stroke
The loop stroke is the distance the needle bar rises from its lowest position to the position where the tips of the eye
looper and right looper are aligned with the center of the needle. The standard loop stroke is 2.7 mm. (The loop
stroke may need changing depending on the material and thread being used.)
* Carry out the adjustment in "4-13. Adjusting the needle and looper timing" before making this adjustment.
1. In the same way as in "4-13. Adjusting the needle and looper timing", move the needle bar to its lowest position
with the needle at the inside sewing position, and then use calipers to measure the distance between the end of
the needle bar (1) and the top of the holder base (2).
2. Add 2.7 mm to the value obtained in step 1. above.
3. Touch the end of the calipers (A) against the top of holder base (2), and then turn the upper shaft pulley until the
end of the needle bar (1) touches the edge of the calipers (B). Check that the tip of the eye looper is aligned with
the center of the needle at this time.
4. In the same way, check that the tip of the right looper is aligned with the center of the needle when the needle is at
the outside sewing position.
3080Q
5. If the tips of the loopers are not aligned with the center of the needle, carry out the adjustment below.
• Raise the machine head.
• Loosen the two screws (3) of the lower shaft timing pulley, hold the upper shaft pulley so that it doesn't move,
and then turn the lower shaft cam (4) in the direction indicated by the arrow until the tip of the eye looper (5) is
aligned with the center of the needle (6). Once they are aligned, tighten the two screws (3).
• After adjusting, check that the screws have been adequately tightened.
• Once this adjustment has been carried out, repeat the procedure given in "4-13. Adjusting the needle and
looper timing".
* Basically, the machine is assembled so that the hole (7) of the lower shaft cam (4) is aligned with the hole (9) of
the lower shaft base (8) when the needle bar is at its lowest position and at the inside sewing position.
3081Q
RH-981A
4. ADJUSTMENT
3079Q
3795Q
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