The Y-axis option has broadened the possibilities to use rotating tools in multi-tasking machines and turning centres. Now this capability has inspired a great innovation in one of the original missions of these machine tool types: Y-axis parting. Implementing this new tool and method brings significant machining improvements in potentially any parting operation.

Adding rotating tools to turning centres means you can combine several set-ups in a single machine for a more streamlined and productive machining process. To accomplish this, turn-mill machines were introduced in the 1990s.

The initial idea was to enable driving a milling cutter, drill or threading tap on one or more tool positions in the turret to eliminate limitations of polar interpolation and other related programming difficulties. To improve reach, an extra set of ways was added to move the rotating tool across the spindle face. This was accomplished by mounting the tools on revolver sides or on its face, by installing the Y-axis ways on a slanted bed or by using an independent milling head.

Both machine tool makers and manufacturers soon recognised the benefits of integrating both milling and turning operations. Today, the Y-axis option has become a standard feature in most multi-tasking machines and optional in many new turning centres.

Given that a potential tool breakage comes with a risk of costly machine downtime or scrapped components, parting off is a stage of the machining process where manufacturers don’t compromise on security. To meet the high demands put on these type of tools, the system CoroCut QD was developed by Sandvik Coromant in 2013.

While considering how to improve this high-performing system even further, the tool developers started looking at these modern machines with Y-axis capacity. This resulted in an innovation that involved more than just the tool design but also a completely new method: Y-axis parting.

The Y-axis parting principle

The principle behind Y-axis parting is incredulously simple. While conventional parting off tools align with the X-axis of the machine tool, the Y-axis tool has simply been rotated 90 degrees anti-clockwise to align with the Y-axis.

In a conventional tool configuration, the relatively long and slender parting blade and holder is fed at a 90-degree angle into the rotating workpiece. The largest cutting force is generated by the cutting speed and the rest by feed motion. The consequence is a resultant force vector that is directed diagonally into the tool at an angle of roughly 30 degrees, in other words across a very weak section of the blade. To avoid tool breakage, this is compensated by reducing the blade overhang and by increasing the blade height, which in turn sometimes compromises the usability of the tool.

By turning the tip seat 90 degrees and utilising the Y-axis, the tool can cut its way into the workpiece essentially with its front end, which nearly aligns the resulting cutting force vector with the longitudinal axis of the blade. Finite element method (FEM) analysis performed by the Sandvik Coromant R&D team confirmed that the new solution eliminates critical stresses and increases the blade stiffness by more than six times compared with conventional blade design.

To cut a long story short, when switching to parting in the Y-axis plane you get a beneficial direction of the cutting force resulting in less instability and vibration. This means you can ramp up feed rate without losing stability or breaking the tool for an extremely secure and productive parting process. Simple as that.