A machine for deburring work pieces, particularly work pieces made from a flat metal plate, by means of brushing or grinding, including: a stationary machine stand; at least one brush unit (4, 5), which is movable vertically relative to the machine stand, including: an endless rotating drive belt; a plurality of brush carriers fastened to the drive belt; brushes for deburring the work pieces, particularly in the form of layers, arranged in the manner of packages, of abrasive paper or nonwoven abrasive, which are located on the brush carriers; characterised by: a rotatably mounted rotary reference disc, which is movable into the working range of the brushes, wherein an upper surface and/or lower surface of the rotary reference disc constitutes a reference plane (16, 17) for the brushes; a device (6, 7) for vertically moving the brush unit (4, 5) into a reference position, in which the brushes contact the reference plane (16, 17) and exert a predetermined pressure on the rotary reference disc, whereby a frictional force between the rotary reference disc and brushes is produced, which induces the rotary reference disc to rotate; a measuring device, which detects the reference position of the brush unit (4, 5). a stationary machine stand; at least one brush unit (4, 5), which is movable vertically relative to the machine stand, including: an endless rotating drive belt; a plurality of brush carriers fastened to the drive belt; brushes for deburring the work pieces, particularly in the form of layers, arranged in the manner of packages, of abrasive paper or nonwoven abrasive, which are located on the brush carriers; an endless rotating drive belt; a plurality of brush carriers fastened to the drive belt; brushes for deburring the work pieces, particularly in the form of layers, arranged in the manner of packages, of abrasive paper or nonwoven abrasive, which are located on the brush carriers; characterised by: a rotatably mounted rotary reference disc, which is movable into the working range of the brushes, wherein an upper surface and/or lower surface of the rotary reference disc constitutes a reference plane (16, 17) for the brushes; a device (6, 7) for vertically moving the brush unit (4, 5) into a reference position, in which the brushes contact the reference plane (16, 17) and exert a predetermined pressure on the rotary reference disc, whereby a frictional force between the rotary reference disc and brushes is produced, which induces the rotary reference disc to rotate; a measuring device, which detects the reference position of the brush unit (4, 5). a rotatably mounted rotary reference disc, which is movable into the working range of the brushes, wherein an upper surface and/or lower surface of the rotary reference disc constitutes a reference plane (16, 17) for the brushes; a device (6, 7) for vertically moving the brush unit (4, 5) into a reference position, in which the brushes contact the reference plane (16, 17) and exert a predetermined pressure on the rotary reference disc, whereby a frictional force between the rotary reference disc and brushes is produced, which induces the rotary reference disc to rotate; a measuring device, which detects the reference position of the brush unit (4, 5).