A Study of Plunge (or Form) Machining of Low-Carbon Resulfurized Steel on a Multispindle Automatic Screw Machine: Part 1—Influence of Speed, Feed, and Ingot Variation on Diameter Increase and Surface Finish in Prolonged Machining

The objective of this investigation was to study the effect of operating variables such as cutting speed, feed, and coolant on surface finish, tool wear, dimensional control, and productivity in prolonged plunge machining on a multispindle automatic screw machine. Low carbon resulfurized and low carbon resulfurized leaded steels were chosen as the workpiece material since these steels account for the bulk of the tonnage used on screw machines. The results show that (a) finer feeds give poorer surface finish than coarser feeds; (b) within the range of feed (0.00049–0.0042 ipr) and speed (86-353 sfpm) investigated, surface finish in plunge machining was found to be more sensitive to changes in feed than to changes in speed; (c) the surface roughness as well as wearland grow rapidly within the first few minutes of the life of a tool, and then attains a much lower rate of deterioration during the remainder of the run until just before the tool failure when the deterioration rate rises progressively; (d) the surface-finish variation is higher in bars obtained from various locations within a single ingot than in bars obtained from similar locations in adjoining ingots; (e) there exists a strong radial variation which gives poorer surface finish and larger diameter increase as the cutting moves from the center of the bar to the outside; and (f) leaded resulfurized steel gives poorer surface finish and greater diameter increase with straight oil than with water soluble oil; the reverse is true for nonleaded resulfurized steel.