The kindest cut

Poorly selected tooling can be the bugbear of even the most sophisticated machinery. Mark Venables previews insert grades, exotic coatings and inserts on view at next month’s MACH 2006.


Any manufacturer will tell you that even the fastest, modern machine can be blighted by poorly selected tooling. So next month’s MACH exhibition will show an immense breadth of offerings — from exotic coatings to strange shaped inserts.

In general steel turning everything varies. The steel material varies from un-alloyed to high-alloyed bar-material through to various forgings and castings. The type of operation carried out varies from rough to finish turning, with conditions ranging from good to difficult.

To meet these demanding requirements, Sandvik Coromant has developed a new insert grade GC4225, which the company claims represents the next generation of P25 grades to enhance machining performance and versatility in the general steel turning area.

Over the past few years the company has carried out extensive R&D so that GC4225 has an improved capacity to adapt to variations in workpiece material and operational demands towards the tougher end of applications. The new black and yellow grade provides fresh potential for increasing productivity through higher cutting data, backed up by improved reliability.

The grade is also more durable, partly through an increased ability to withstand thermal demands. As such it has shown itself to be even more suitable for various optimisation requirements within the very broad area of general steel turning.

A combination of improved insert toughness and wear resistance has contributed to GC4225 becoming a better all-round grade. It is a multi-talented solution and through improved coating adherence has considerably elevated the edge-line security of inserts.

This makes it possible to use a P25 grade throughout an even wider area than before. So it is especially advantageous for machine shops with varying one-off component production, while at the same time retaining the ability for higher metal-removal-rate optimisation for large-volume machining.

Also on show will be the QuattroMill general-purpose face milling cutter from Seco Tools that incorporates the latest technology for high productivity milling with extended tool life.

For example, the cutter’s positive, light cutting geometry generates less force, and consumes less torque, making it ideal for use on low-power machines, for difficult materials including hardened steels, stainless steel and superalloys, and for applications where a close-pitch cutter style is preferred.

The light cutting action also significantly reduces vibrations and noise. Because the cutters and inserts are produced with tight manufacturing tolerances, extremely fine surface finishes are achieved. These characteristics also make it ideal for unstable conditions including long overhangs or poor fixturing of the workpiece.

The thick, strong inserts used with the cutter allow milling at very high feed rates. The available wiper inserts also enable milling with extremely fine surface finishes. The inserts, which are held by an extra-long locking screw, have an integrated anvil to protect the insert pocket. This design minimises spare parts and enables quick and easy indexing of the inserts without fully removing them from the cutter.

This has an extremely hard surface coating — 800 Vickers (approx 64HRC) — that extends tool life by protecting the body from wear and corrosion. The coated body also enhances chip flow from the pockets, an added advantage with close pitch cutters that have smaller chip flutes due to the additional teeth.

When it comes to turning cast iron, it demands a lot from cutting materials, which is where Ceratizit’s HyperCoat-C CTC3110 comes into its own. The new high-performance grade is based on a recently-developed substrate that combines the necessary toughness and heat resistance thanks to its specially-adapted composition and grain size.

The coating — combining titanium carbonitride with a special structure, and a multi-layer aluminium oxide coating with a special atomic arrangement — provides maximum wear resistance, despite temperatures above 1,000ºC, hard casting skin and irregular cutting depths which are common when machining cast iron.

The finish, which provides the cutting inserts with a shiny surface, is a final refinement that protects the cutting edge and provides customers with easy-wear detection.

Tests with HyperCoat-C CTC 3110 at producers of grey cast iron components such as brake disks and drums, differential casings and pulleys have convincingly demonstrated tool life increases of between 35 and 100 per cent.

Tooling for confined spaces is something that Iscar has experience within its Swisscut tooling systems. This high-precision system is designed to work reliably in a confined space and on tough workloads without colliding with other tools on the turret while in operation.

A vast amount of human engineering has been invested in toolholder design, to guarantee easy and ergonomic engagement with the gang plate.

The toolholder has back and front clamping features, which hold the uniquely designed inserts in an accurate position. The bottom and back prisms on each provide better stability and precise positioning of the insert, particularly when applying high shearing loads, or when turning in alternating directions.

The major advantages of using these toolholders are that they can be clamped without removing them from the machine turret, plus the ability to clamp and release the insert from either side of the toolholder.

This mechanism comprises a threaded bushing and a screw that pulls the insert back into the pocket, using the bushing.

Moreover, the tightening screw is locked, preventing it from falling out of the pocket during indexing. An alternative option for clamping is a frontal one, comprising a semi-standard version for a toolholder without the bushing element.

The inserts themselves are made of grade IC1008, comprising a submicron substrate with TiAlN and TiN PVD-coated layers. This combination guarantees excellent performance during the machining operation, as well as prolonging tool life.

The grade demonstrates toughness coupled with relatively high hardness, ideal for machining exceptionally small applications. In addition, the grade also provides remarkable notch wear and built-up edge resistance.