Tooling application strategies for parting-off, grooving

The basic goals of parting-off and grooving processes are the same as those for general turning operations: achieving the desired shape of the part being machined, meeting specifications for accuracy and maximising productivity. In addition, however, parting-off and grooving applications are distinguished by specific issues in regard to tool strength and rigidity as well as chip control. Tool manufacturers employ innovative tooling designs as well as advanced coolant delivery strategies to meet the special requirements of parting-off and grooving processes.

Tooling for parting-off and grooving

Like general turning operations, parting-off and grooving processes involve rotating a workpiece and cutting it with a stationary tool. The first consideration is configuring a cutting tool system that will produce the desired part shape. As a result, the designs of parting-off and grooving tool systems vary according to the size and depth of the features being machined. For deep grooving and parting-off operations on large parts, as well as for shallow grooving and cut off on smaller parts, tool manufacturers, for instance, will offer on-edge or tangential-configuration parting-off and grooving inserts that are clamped directly in a holder.

One example is Seco Tools new line of star-shaped tangential design inserts with four cutting edges called the X4 series. Available in cutting widths from 0.5mm–3mm (0.02”–0.12”), the inserts are engineered to minimise material consumption in parting-off and enable precise grooving and copying of small and medium-sized complex parts. Depending on the cutting edge width, the tool’s maximum cutting depth ranges from 2.6mm- 6.5mm (0.10”– 0.26”) and can cut off maximum bar diameters from 5.2 to 13 mm (0.20” to 0.52”). The inserts’ tangential design directs cutting forces into the holder to maximise rigidity, stability and productivity.

Following determination of the basic insert shape, choice of the lead angle of the cutting edge is a key factor in parting-off and grooving effectiveness. A zero-degree lead angle tool provides perpendicular alignment to the workpiece and transfers cutting forces directly into the toolholder, which enhances accuracy, tool life and surface finish. As parting-off is completed, however, a zero-degree tool leaves a small knob or pip at the centre of the bar being cut off. If the pip is undesirable, using a tool with a slight lead angle will cut off the pip as it passes through the centre of the part. Lead angle tools also are less prone to generate burrs in some workpiece materials.

After the basic tool configuration is set, workpiece material characteristics generally dictate the insert grade that will machine a part most efficiently. A tough workpiece material or interrupted cut will indicate use of an insert grade biased towards strength and impact resistance, while a particularly abrasive workpiece will require an insert grade engineered for wear resistance. Tool coatings such as Seco’s Duratomic? CVD aluminium-oxide coating are used to fine-tune tool characteristics for specific workpiece materials and toolpaths.

Application recommendations

There are certain specific setup recommendations for parting-off and grooving tools. Care should be taken to mount the tool so the blade is truly perpendicular to the axis of the workpiece. This minimises axial forces on the tool and will prevent rubbing on the sides of the insert. Regarding tool position, the centre height of the cutting edge should be as close to the centre of the workpiece as possible, within +/- 0.1Adidas Glitch Skin