A few days ago, we received a video from a customer reporting that their lathe produced a brief metallic impact sound (similar to a “clack”) during startup or emergency stop.
In response to this phenomenon, we have summarized the possible causes as follows for your reference.
1. Chuck jaw clearance (most likely cause and a normal phenomenon)
The chuck is running without holding a heavy workpiece. There is always a small structural clearance between the chuck jaws and the guide slots. When the spindle starts or stops abruptly, due to inertia, the jaws may move slightly and impact the walls of the guide slots, producing a noticeable metallic “clack” sound.
We recommend performing a test: please use a solid steel bar or a thicker cylindrical workpiece, clamp it firmly, and then start and stop the machine again. If the noise completely disappears, it indicates that this is a normal clearance phenomenon caused by jaw inertia, and the machine itself is in proper working condition.
2. Spindle gearbox gear backlash
The gears inside the lathe’s gearbox inherently require a certain amount of backlash for proper meshing. During sudden startup, the gears shift instantly from a clearance state into full engagement, which may generate a brief impact noise. If the noise persists even when the workpiece is properly clamped, it may indicate slight clearance in the keyway, or that the locking nut needs to be inspected, readjusted, and tightened.
3. Spindle brake adjustment issue
If the mechanical or electromagnetic brake is too tight, or if it does not fully release during startup, it may cause noticeable friction or impact noise when the spindle starts or stops.
Suggested checks:
Ensure the brake releases completely
Verify that the brake clearance is within the standard range
4. V-belt or pulley issue
If the V-belts between the spindle box and the motor are too loose, they may slip or vibrate during startup. In addition, wear in the pulley keyway may also lead to mechanical impact noise, although this is generally not a primary cause
Post time: Jun-12-2026