Reversion of rotation
Possibility to operate the sanding unit not only in the down-cut, but also in up-cut direction (workpiece feed and abrasive work in the same direction).
Usually the sanding belt of sanding rollers and the brush or the sanding carcass resp. rotate in the down-cut against feed direction in order to achieve high chip removal. In some cases it depends less on a high chip removal, but on a clean cut of wood fibres created during calibration. In other cases sensitivity is key, e.g. when sanding veneers or surfaces already-lacquered.