AN ANALYSIS OF CUTTING TOOLS WITH NEGATIVE SIDE CUTTING EDGE ANGLES

With the advent of numerically controlled machines the problem of faci ng and turning with the same tool was solved by the use of negative si de cutting edge angles (SCEA), also known as lead or approach angles. The development of 80 degrees diamond shaped inserts have made them mo re versatile not only for use with -5 degrees but also with 0 degrees and 15 degrees SCEA's, Despite their success, their performances have not been analyzed and reported in textbooks or in journals. Three tool s with SCEA's of -5 degrees, 0 degrees, and +15 degrees were used to m achine low carbon steel (1018) at speeds of 450, 560, and 710 sfm at a depth of cut of 0.1 and a feed of 0.01 ipr. Cutting forces were measu red and friction and shear plane angles determined. Chips and chip roo ts were analyzed for secondary shear zone formation. Chips were sorted into nine distinct-color categories using digital color imaging techn iques. Surface roughness and roundness, and brightness measurements we re made. Results indicate that the tool with -5 degrees SCEA performed better than the other two and the reasons for this are highlighted in this paper.