Machine Cutting Tools

Machine Cutting Tools Today:

All these and more are still being used today, some have progressed from simple metallic Machine cutting tools made of high-speed steels, to cemented carbides with hard metals like tungsten carbides being used as 'inserts'. These Machine Cutting Tools inserts made the life of the machinist easy, because they were harder [and hence perishable, or breakable by jerks, jolts or sudden dynamic loads] but longer lasting than the tougher metallic tools.

Polycrystalline Diamond and PCBN cutting tools are the Machine Cutting Tools of the future, ideally suited to advanced production techniques and machining of abrasive materials.

PCD [Poly-Crystalline Diamond]: For machining non-ferrous materials, carbon, ceramic, fiberglass composites, plastic and rubber.

PCBN [Poly Crystalline Cubic Boron Nitride]: For machining hardened ferrous materials, tool steel, alloy steel and cast iron.

Cubic boron nitride - a ceramic with magical properties increased the cutting speeds from a mere one-meter per second to ten metres per second and higher. One cannot ignore the huge problems, posed by such monstrous feed-rates. The work piece would heat up to nearly the melting point of the steel, and the cutting tool would get welded to the same. This is called galling, and it is virtually a nightmare for the machinist, quite capable of totally ruining not only the cutting tool but destroying the work piece in the process too.

Then comes the rigidity problem. No metal will remain hard at temperatures beyond seven hundred degrees Celsius while in high speed machining today much higher surface temperatures are routinely encountered, and dealt with very competently. No softening of the tool takes place. The coolants and lubricants used, have had to march along with the progress in cutting tool materials, their specialised inserts made of hard-metals like carbides, and their more and more specialised thin film coatings.

The advent of coated tools, half a century ago revolutionised the cutting tool industry. Just a thin film of one or two microns of some super hard ceramic e.g., titanium nitride, most widely seen in industry for decades as the shining golden coating that may be up to 84 HRc hard [while the best of the HSS cutting tools in earlier eras were barely up to 68 or 70 HRc max. Alloyed ceramics like aluminium titanium nitride, titanium carbo nitride and many more arrived on the scene, removing a host of problems for faster cutting, even the traditionally difficult non-ferrous metal/alloy cutting e.g., copper alloys, aluminium and its alloys, titanium and its alloys.

Suitable for fast, smooth and steady cutting of hard-fragile non-metal material, such as concrete, marble, granite, tile, etc., with the advantages of excellent cutting performance. Especially Turbo Blade with wave core, its wave core design greatly improved the rigidity of the core.

Diamond-like coatings, very thin and very hard, also appeared and have been enjoying a long run now with their higher costs but equally higher performance. Nano-technology has now joined as one of the most promising new entrants on a very competitive field, where the user in India is thoroughly confused about such a wide variety of coatings, technique, combinations and their mixed economics need expert guidance.

What is Happening Today Machine Cutting Tools: Here is a gist of some of the ongoing research in European nations, just to give the reader a flavour of what can be expected in next two years or so:

• Dry machining concepts for precision turning of steels and bronzes - dry machining sequences of aluminium parts - minimal lubrication techniques for machining.

• Environmental friendly cooling lubricants - alternative gaseous coolant techniques for machining

• Machine tools adapted to the requirements of dry machining - coated cutting tools for dry machining application.

• Targets have been set for the properties of cutting tool materials to be developed depending somewhat on the particular class of materials but in general a minimum hardness of 1500 Vickers and a minimum toughness of 8 MPa m% is thought necessary for the intended applications; [compare that with hardly 900 Vickers as the bulk hardness of HSS -the most commonly used metallic tool material today],

• Chemical compatibility with the workpiece material will be another be it difficult to quantify attribute of the new materials and coatings systems. CVD, MTCVD and PVD coating technology will be used. A total of 12 new materials or material/coating combinations are to be developed. About 870 tools will be produced and tested. The accompanying research on shape of the tool and on machining conditions is expected to lead to the following productivity increases for drilling in steels a factor of 4 and in A1Si a factor of 8.

This is an "intelligent" cutting insert which Kyocera [Japan] has specially developed for the mass production industry - for the manufacture of brake disks, for example. This was a case where the company made use of its own synergies by adapting a technology employed in its electronics division for the purpose of tool production. The principal focus of the tool system is on cutting costs: the Sensor Tool System detects undue wear and tear or damage right at the cutting edge and alerts the machine control immediately. This method provides an automated process check and reduces the amount of scrap and spoilage accordingly.

Going Beyond Today's Machine Cutting Tool Materials

Super Material Abrasive Resistant Tools or SMART*CUT [CSIRO Australia] technology uses thermally stable diamond composites (TSDC) in the design and manufacture of cutting tools for mining, civil construction and manufacturing. TSDC is more than 1,000 times more resistant to abrasive wear than tungsten carbide (WC). TSDC easily overcame the thermal instabilities limiting traditional diamond composites but it posed a vexing bonding problem.

CSIRO has developed a reliable bonding process and is prototyping drill bits and other cutting tools to take advantage of TSDC's unique properties. Laboratory drilling trials have demonstrated that these prototype bits have twice the penetration rate and expend half the energy of traditional rock coring bits.

In the manufacturing industries, indexable cutting inserts incorporating TSDC would offer several important advantages over tungsten carbide. Such tools are expected to:

* Operate at higher cutting temperatures

• Eliminate or at least reduce the need for environmentally damaging cooling fluids

• Enable faster and more economical high-speed machining operations.

Acknowledgement: Various inputs from the Internet, the names of laboratories, vendors, or innovators have been mentioned wherever available.