Small Nose Radius Research Articles

The application of a turning tool as the electrode in electropolishing

In the current study, electropolishing using a turning tool as the electrode for several die materials following turning is investigated. The proposed method uses a traveling electrode instead of the mating electrode as in conventional ECM, hence the dimensional error can be controlled more effectively. Further, the method removes a certain limited amount of material, therefore the complex pre-polishing as required in the soakage electropolishing method is eliminated. This process can be used for various turning operations including end turning, form turning, and flute and thread cutting. Through the attachment of simple equipment, electropolishing can follow the cutting on the same machine and chuck. The electrode of the turning tool travels and polishes the machined surface of workpiece with electrical current. Among the factors affecting the electropolishing, the design of tool electrode is discussed primarily. A common turning tool can be used in electropolishing, while a slight modification of tool geometry achieves optimal polishing at low cost. The controlling factors include the chemical composition and concentration of the electrolyte, the initial gap width, and the flow rate of the electrolyte. The experimental parameters are the current rating, the electrode geometry, the die material, the workpiece rotational speed, and the electrode feed rate. Turning tools with larger angles and smaller cross-section are associated with larger discharge space and thus polish better. The most significant factors in tool design for improving the surface roughness include the end clearance angle and the end cutting edge angle. A smaller nose radius is associated with higher current density and provides a faster feed rate and a better polishing effect.

Some Observations of the Surface Roughness of Mild Steel Finished by Turning

The surface roughness of metals finished by turning has been treated as a problem determined geometrically by the geometry of cutting tools composed of a nose radius and end- and side-cutting-edge angles and the rate of feed. It has also been regarded as being affected adversely by such factors as a build-up edge, the boundary wear at the end-cutting-edge and vibration in the system of the tool and work being machined. It is commonly known, however, that the surface roughness of low carbon steel depends on the depth of cut and the side-cutting-edge angle when it is machined by a cutting tool of a small nose radius. Another factor may have to be introduced to account for this phenomenon. In this paper, microphotographs of that part of work being machined from which chips are separated at the end-cutting-edge of a cutting tool were observed to examine the effect of the condition of chip separation on the surface roughness. It is expounded that the above-mentioned phenomenon can be accounted for by a new factor based on the chip formation mechanism which has an adverse effect on the surface roughness ; the factor being divided into four elements : (1) burrs on the work being machined at the end-cutting-edge of a tool, (2) burns on chips at the end-cutting-edge, (3) fluctuations of feed force and (4) the secondary contact between chips and the surface which has been just machined.