Abstract: A coordinate measuring machine (10) is disclosed of the type having a bridge (28) mounted for horizontal movement of a base (30), a carriage (24) mounted for horizontal movement in a direction orthogonal to the direction of bridge movement and a probe (12) mounted for vertical movement on the carriage (24), so that the probe (12) is guided along three orthogonal axes over a table (14) supported on a base (30), so as to enable measurement of an object (16) disposed on the table (14) by measuring the extent of travel along each axis. Side covers (42, 50) are provided fastened to the base (30) and enclose the lower ends of upright members (40) comprising in part the bridge (28) so that the bridge (28) movement is confined within openings (44) formed by the side covers (42, 50). A dust covering movable belt (46)is attached at either end to each upright member (40), closing off the openings (44 ), the belt (44) recirculating as the bridge moves.