1. The axial planes of the upper shaft, vertical shaft and lower shaft have no gap or no gap on one side, which makes the rotational force of the machine too large; check the axial plane matching of the three shafts. It is required that there is a gap in the plane matching, but not greater than 0.04mm, easy to turn
2. The thread take-up crank and the thread take-up connecting rod pin of the thread take-up rod assembly have no clearance or unilateral clearance in the axial direction, so that the machine has a large turning power; no obvious resistance
3. The clearance between the parts of the tooth-lifting and cloth-feeding mechanisms is too small, which results in a large turning force of the machine; check the clearance between the parts and make reasonable adjustments
4. There are backlogs such as fluff and piles between the top of the feeding dog (the part below the needle plate) and the needle plate; remove the needle plate and remove the backlog on the feeding dog
5. There are sundries in the rotary hook (the thread is rolled and the thread is broken after the thread is broken); the sundries in the rotary hook should be removed, and some sewing machine oil should be added.
6. After the exchange-type correction parts, the turning force of the machine is large; the quality of the parts is not good, such as the concentricity, straightness, and parallelism are not good. Measure or replace a part for comparison
7. The matching clearance of the bevel gear is too tight; properly adjust the meshing clearance of the bevel gear
