1. Loose tool holders or worn slide inserts can cause tool holders to swing. As a result, the parts may be scratched, so before machining the metal parts, it is necessary to check whether the tool holder is securely installed and ensure that it cannot be moved by hand.

2. Severe bearing wear can also lead to this possibility, and at this point, the bearing must be replaced.

3. If the chuck is adjusted too loose or the opening and closing claws are too loose or damaged, the chuck may not grip the material tightly when the chuck is too loose, which can cause the material to retreat and have knife marks; When the opening and closing claws are too loose or damaged, it can also cause the chuck to not grip tightly or the opening and closing claws to be under unilateral force. It is necessary to replace the opening and closing claws or check the tightness of the chuck more frequently.

4. The fixing screws of each transmission connecting rod are not locked tightly or have gaps that are loose, and the compression or tension springs of each part are too loose, which can cause the tool to shake and produce knife marks.