Tula State University, Tula, Russia:

A. S. Yamnikov, Professor, e-mail: Yamnikovas@mail.ru

A. I. Kharkov, Postgraduate Student

SPLAV Research & Production Association, Tula, Russia:
О. А. Yamnikova, Professor, Category I Expert

Tulsky Oruzheiny Zavod, Tula, Russia:
А. О. Chuprikov, Head of Department

Today’s manufacturers are ready to offer a wide selection of changeable multifaceted cutters made of hard metal ceramic alloys and designed for threading blanks made of high-strength alloys. The recent decades have seen an increasing scope of applications for changeable multi-faceted ceramic cutters, which are extremely hard and have high red hardness characteristics at high temperatures occurring in the cutting area. The application of ceramic cutters is limited due to their brittleness and insufficient bending strength. An experimental study was conducted to understand the effect of relief angles along the side and top blades; the size and the slope of the strengthening chamfer around the cutting blade on the wear resistance of the VOK 60 ceramic cutters operated as advised by the manufacturer and verified by field trials. A wear of 0.2 mm along the rear surface of the thread cutter was taken for the wear criterion. The face of the thread cutter (in particular, the width of the crater and the band between the cutting edge and the crater) was also monitored for wear. During the experiment, the relief angle on the top and side blades was increased from 2 to 10 degrees with a 2-degree step. The authors found that smaller relief angles (α = 2 degrees) are associated with a higher wear intensity along the rear surface, while the relief angles bigger than 6 degrees can lead to cutting edge chipping. The recommendation is to use blades with relief angles in the range of 5 degrees ± 30'. The authors also looked at the relevance of practices employed by Sandvik Coromant who advise using a strengthening chamfer with a negative rake angle. Because the surfaces that need to be processed are quite large, the threading operation was substituted with a longitudinal turning operation, with the shape of shavings being very similar to that resultant from thread cutting. A 20-degree angle and a 0.2 mm wide chamfer should be considered an optimum combination in terms of achieving maximum durability.

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