The invention discloses a machining device for a machining tool. The machining device structurally comprises a power distribution cabinet, a control cabinet, a transverse sliding rail, a longitudinalsliding rail, a cutter clamping groove, a movable rectangular supporting column, a cutter, a workpiece, a workpiece thread groove machining device, a scrap input groove, a fixing framework, a scrap collecting box, a base and trundles. According to the workpiece thread groove machining device, a workpiece rotating driving mechanism can fix workpieces of different models and drive the workpieces torotate uniformly, by means of the lead axial turning mechanism, in the rotating process of the workpieces, the cutter can be driven to move accurately and uniformly in the axial direction of the workpieces, thus, precision and efficiency of thread workpiece production are improved, by means of the scrap collecting mechanism, scraps and metal dust generated in the turning process can be collected automatically, the scraps can be reutilized, and while the production cost is reduced, the metal dust is prevented from polluting air.