Page 427 - ISCAR(TURNING-CATALOG-42-2022)
P. 427

USER GUIDE




          Recommended Criteria for Replacement of the Cutting Edge

              The cutting edge should be replaced in time to save   Crater Wear and Tool Life                         GROOVE-TURN
              costly downtime. The recommended value of wear    Crater wear KB occurs on the rake face and is mainly
              at replacement is defined as the wear land size. The   affected by feed and cutting speed. Crater wear
              insert should be replaced when the wear land size   develops over time toward the frontal cutting edge.
              is such that the increase in side forces is still small-  If penetration of the frontal cutting edge occurs, it will
              not causing the insert to break and still maintaining   immediately affect the quality of the machined surface.
              the required workpiece tolerances. Wear is a function
              of machining time. The cutting edge should normally
              be replaced after 15 minutes of machining time.

              Insert Wear-Tool Life Wear on the Clearance Face
              Wear land on groove turn inserts generally occurs at the
              corner of the clearance face VBN, on the side near the
              corner VB, on the frontal cutting edge VBF and at the end             KB
              of the cutting side VG. The effective life of the cutting edge
              ends when any of the wear land values-VB, VB, VBF or
              VG-exceed the recommended maximum values shown.
              The largest wear land is normally measured at the corner
              of the clearance face VBN. It has the most influence on
              the dimensions and tolerances of the final workpiece.
              The wear land shape on GRIP inserts differs slightly from
              that of ISO inserts. Although the frontal cutting surface   Plastic Deformation
              of GRIP inserts absorbs more heat land wear, the wear   Plastic deformation occurs when the hardness of a
              land VBF is generally negligible in turning operations   cutting edge is decreased due to heat and pressure.
              when compared to VB and VBN. Wear may be found    The so-called “hot hardness” of the cutting tool material
              only occasionally at the end of the cutting side VG.
                                                                limits the feed and the cutting speed.
                                                                Plastic deformation will affect the dimensions and
                                                                tolerances of the finished product. It generally occurs
                                                                when a small corner radius is used with high cutting
                                                                speeds and high feeds. Using the proper insert
                                                                geometry and the correct speed and feed
                                                                ranges should eliminate the problem.
                                      VG

                       VBF
                                  VB
                        VBN                                                                                           TEXT


              Maximum recommended wear land
              values relative to insert widths
                        W                  Maximum
                  Insert Width (mm)      Wear Land (mm)
                        ≤3                   0.20
                        4                    0.22
                        5                    0.25
                        6                    0.27
                        8                    0.27
                        ≥10                  0.30























                                                                                                                   425
   422   423   424   425   426   427   428   429   430   431   432