Brother LH4-B800E Service Manual download pdf (Page 114)

LH4-B800E

4 - 27

4. Adjustment

F = 98 N (10 kgf)

4-21. Adjusting the upper shaft timing belt

1. Loosen the screws q, and then use a spring gauge to push the notch in the tension pulley plate w with a force of

98 N.

2. Tighten the screws q.

If you do not have a spring gauge, adjust the tension so that the amount of belt deflection is approximately 5 mm when

a force of 5 N is applied in the middle of the belt span between timing pulley U e and the idle pulley r in the place

indicated by arrow A.

4-22. Adjusting the rotary hook lubrication

To oil tank

Less

1. Remove the rubber stopper q.

2. Turn the adjusting screw w to adjust the lubrication amount.

* Adjust so that approximately 10 drops of oil are released when the sewing machine is run at a speed of 4000 rpm

for three cycles to sew about 114 stitches. Use Kraft paper e or similar to catch the oil drops. As a guide, the

optimum position can be obtained if the adjusting screw is tightened as much as possible and then loosened about

two turns.

* If the lubrication amount has been reduced, run the machine for 200—300 sewing cycles and then check it again.

If lubrication stops, it will cause problems such as rotary hook seizure and thread breakages.

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Brother LH4-B800E Service Manual Page 114