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Tham khảo tài liệu 'machinability and surface integrity part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Machinability and Surface Integrity 339 the cutting insert or tool they are most familiar with because they know - from practical experience - that it performs and wears in a progressive manner rather than the unpredictability associated with an insert of uncertain machining capability that might otherwise prematurely fail. Prior to discussing criteria for determining when a cutting insert is worn-out it is necessary to establish in practice what this actually means. For example does worn-out refer to when the dimensional accuracy becomes unpredictable or if the surface finish has significantly deteriorated or perhaps the fact that its automatic chip-breaking behaviour has become inefficient In many situations it is by the user s experience that one can judge how much flank wear can be tolerated on the cutting edge before machining is discontinued. As a rule flank wear is a dependable criterion for assessing when the cutting edge is effectively worn-out. Moreover from the previous discussion perhaps the degree of cratering may in certain machining circumstances prove to be more significant than the flank wear in respect to the shortening tool life. Tool wear can be established by several techniques but the usual method is to observe and then measure the actual wear as it progressively develops. The effective cutting time or tool life T is specified as time-elapsed prior to a predetermined degree of wear has been reached. A typical procedure for determining flank wear can be to observe cutting edge s in-situ on the machine tool then remove from the machine and visually inspect the tooling followed by its respective wear rate can then be optically magnified in suitable equipment allowing accurate dimensional measurement - against the following criterion i.e. see Fig. 174 Extent of flank wear from original edge - if this wear is of relatively uniform nature it may be distributed across three zones A B and C . The mean flank wear Vb C-a is measured over the cutting .
