Method for monitoring a sanding process in which a disc-shaped workpiece is sanded in a belt sanding machine, wherein the belt sanding machine has a sanding head which comprises a contact roller and/or a sanding shoe and at least one deflection roller, wherein a sanding belt is guided by the at least one deflection roller or jointly by the at least one deflection roller and the contact roller, wherein the belt sanding machine has a feed device for moving the workpiece relative to the sanding head during the sanding process, wherein the sanding belt is pressed onto a surface of the workpiece by the contact roller and/or by the sanding shoe during the sanding process, wherein the belt sanding machine is also assigned a sensor unit for scanning the surface of the workpiece, which is connected to an evaluation unit, characterized in that the sensor unit scans the surface of the workpiece after the sanding, wherein the sensor unit and the evaluation unit detect the roughness of the surface of the workpiece and, in the event of a change in a setting of the belt sanding machine, detect the roughness both before and after the change is made, wherein the sensor unit and the evaluation unit are set up to detect the presence of at least one chatter mark, wherein, if at least one chatter mark is present on the surface of the workpiece, a property and/or a condition of the at least one chatter mark is detected by the sensor unit and the evaluation unit, wherein the condition of the chatter mark is used to determine whether the chatter mark is caused by a belt connection of the sanding belt and/or by the contact roller and/or by the feed device and/or by another component of the belt sanding machine, wherein measurement data recorded by the sensor unit and evaluated by the evaluation unit are compared with predetermined limit values, wherein a signal is output if a predetermined limit value is exceeded or not reached, wherein, for monitoring the sanding process, the sensor unit is expediently arranged downstream or behind the sanding head in the feed direction in order to scan the surface of the sanded workpiece, whereby at least one of the following actions is then carried out depending on the measurement data recorded and/or depending on the signal output: - Stopping the belt sanding machine or the sanding process, changing at least one setting of the belt sanding machine, whereby non-contact sensors, such as optical sensors, are used. wherein the belt sanding machine has a sanding head which comprises a contact roller and/or a sanding shoe and at least one deflection roller, wherein a sanding belt is guided by the at least one deflection roller or jointly by the at least one deflection roller and the contact roller, wherein the belt sanding machine has a feed device for moving the workpiece relative to the sanding head during the sanding process, wherein the sanding belt is pressed onto a surface of the workpiece by the contact roller and/or by the sanding shoe during the sanding process, wherein the belt sanding machine is also assigned a sensor unit for scanning the surface of the workpiece, which is connected to an evaluation unit, characterized in that the sensor unit scans the surface of the workpiece after the sanding, wherein the sensor unit and the evaluation unit detect the roughness of the surface of the workpiece and, in the event of a change in a setting of the belt sanding machine, detect the roughness both before and after the change is made, wherein the sensor unit and the evaluation unit are set up to detect the presence of at least one chatter mark, wherein, if at least one chatter mark is present on the surface of the workpiece, a property and/or a condition of the at least one chatter mark is detected by the sensor unit and the evaluation unit, wherein the condition of the chatter mark is used to determine whether the chatter mark is caused by a belt connection of the sanding belt and/or by the contact roller and/or by the feed device and/or by another component of the belt sanding machine, wherein measurement data recorded by the sensor unit and evaluated by the evaluation unit are compared with predetermined limit values, wherein a signal is output if a predetermined limit value is exceeded or not reached, wherein, for monitoring the sanding process, the sensor unit is expediently arranged downstream or behind the sanding head in the feed direction in order to scan the surface of the sanded workpiece, whereby at least one of the following actions is then carried out depending on the measurement data recorded and/or depending on the signal output: - Stopping the belt sanding machine or the sanding process, - Stopping the belt sanding machine or the sanding process, changing at least one setting of the belt sanding machine, whereby non-contact sensors, such as optical sensors, are used.