First check whether the thread is threaded incorrectly and whether the bobbin case is stuck properly. If these are all right, it means that the upper thread is loose or the bottom thread is tight. Just fine-tune it.
If it is determined that the lead wire is correct, the reason is that the thread clamp has lost its function. Perhaps the thread clamp between the two discs of the thread clamp will affect the tightness, or the tension of the clamp pagoda spring.
Extended information
Components
General sewing machines are composed of four parts: machine head, machine base, transmission and accessories.
1. The head is the main part of the sewing machine. It is composed of four mechanisms of material stabbing, thread hooking, thread take-up and feeding, and auxiliary mechanisms such as thread winding, material pressing, and tooth dropping. The motion of each mechanism is reasonably coordinated, working in cycles, and sewing the sewing materials together.
2. The base is divided into two forms: table plate and chassis. The table of the table type machine base plays a role of supporting the machine head, and is used as a work table during sewing operations. There are many styles of tabletops, including one or more buckets of folding Tibetan type, cabinet type, writing desk type, etc. The case of the case type machine base plays a role of supporting and storing the machine head, making the sewing machine easy to carry and store.
3. The driving part of the sewing machine is composed of parts such as frame, hand crank or motor. The frame is the pillar of the machine, supporting the platform and pedals. When in use, the operator steps on the foot pedal, the crank drives the rotation of the pulley, and the belt drives the head to rotate. Most hand cranks or motors are directly mounted on the machine head.
4. The accessories of the sewing machine include needles, bobbins, screwdrivers, oil cans, etc.
Machine maintenance
1. Refueling parts
(1) Each oil hole on the machine head lubricates the upper shaft and the parts connected to the upper shaft.
(2) The internal parts of the panel and the movable parts connected to each part. Lubricate the presser foot bar, the needle bar and the parts connected to it.
(3) Wipe the movable parts of the lower part of the machine board and add less oil.
(4) The refueling amount of each refueling hole and refueling part does not need to be too much, just one or two drops.
2. Maintenance
Secondly, the following points should be paid attention to when maintaining the sewing machine:
(1) After the work is finished, insert the needle into the needle hole plate, raise the presser foot, and cover the machine head with a machine cover to prevent intrusion of dust.
(2) When starting to work, first check the main parts, how light and heavy it is when you step on it, whether there is a special sound, whether the needle is normal, etc. If any abnormality is found, it should be overhauled in time.
(3) After the machine has been used for a long period of time, a major repair should be carried out. If parts with larger wear are found, replace them with new ones.
