A STUDY OF THE BUILT-UP EDGE IN DRILLING WITH INDEXABLE COATED CARBIDE INSERTS

Indexable drills, with different geometry and coating materials on car bide inserts, manifest significant differences in drilling performance , including hole quality and tool wear. Though drilling was done at 71 m/min in a copious cutting fluid environment, a large built-up edge a nd not secondary shear formation was observed, contrary to our expecta tions. On the other hand, when turning under the same cutting conditio ns a very small built-up edge was observed. To study how geometry and coating materials of carbide inserts affect the drilling process, buil t-up edges on chip roots were studied. A novel explosive quick stop de vice used to obtain chip roots in drilling experiments was developed. By studying the built-up edge on the chip roots, some reasons have bee n found to explain the influence of geometry and coating materials and these are presented in this paper.