A bearing block assembly (100, 102) for a plant-trimming machine (10) having a rotatable perforated tumbler (18), a rotatable reel (26) and a bed bar assembly (32). The bearing block assembly (100, 102) comprises an outer bearing plate (104) having a bearing-receiving bore (110) for holding a reel bearing (111) to rotatably support an end of the reel, and an inner bearing plate (106) affixed to the outer bearing plate. The inner bearing plate has a pocket (112) for receiving the bearing-receiving bore (110) of the outer bearing plate, the pocket (112) having a tolerance permitting the bearing-receiving bore (110) to be set at a selected position within the pocket. The inner bearing plate also has a contact surface (118) for engagement with the bed bar assembly (32) and a bore (120) for receiving a tumbler bearing for a rotatable tumbler support (20D). The bearing block assembly has connectors (117) for affixing the outer bearing plate to the inner bearing plate. The bearing block assembly sets the positions of the reel, bed knife and tumbler correctly during assembly of the plant- trimming machine, reducing the time and skill required for maintenance.