Estimation of the rotational speed limit of milling cutters with screwed indexable inserts

During the process of high speed cutting (HSC), fast rotating milling cutters are subject to much higher centrifugal forces than cutting forces. This fundamental factor requires to take into account more stringent safety considerations when working on the concept and design of HSC tools. This paper focuses on the operational safety and speed limit of commonly used HSC milling head cutters with indexable inserts being clamped by high-strength countersunk head screws. The spin burst test results of those tools with radial and tangential insert connections are summarized. The analytical formulas to estimate the failure speeds of both insert connections are developed and discussed based on theoretical analysis on insert connection mechanism. Calculation results show a good correlation with the experimental results from spin burst tests. Finally, a new analytical-empirical approach to determine the speed limits and maximum permissible rotational speeds of both types of tools based on a high confidence level is presented. The approach proposed is suggested for a reliable estimate of the speed limits and maximum permissible rotational speeds for fast rotating tools with screwed radial or tangential indexable inserts.