Specialised drills save machining costs

Six drilling developments shown by Kennametal at EMO 2007, included hole making in SS and carbon-fibre reinforced polymers, deep-hole drilling and a modular drilling system, reports Mike Page.

As commercial pressures grow to reduce machining costs in the established industrial countries, so the demand for more specialised drilling products grows.

It is no longer economically viable to live with long drilling cycles using standard, low cost drills or endure regular regrinding of such drills.

Consequently, drill suppliers have been paying more attention to the problems of improving hole-making performance in 'difficult' materials, like stainless steels and carbon-fibre reinforced polymers.

Also, deep-hole drilling technology has advanced considerably, reducing cycle times and improving surface finish.

To overcome the overhead costs problems of maintaining larger stocks of specialised tooling, a number of companies have introduced modular drilling systems.

Typically, a standard shank accepts a range of modular drilling heads.

Great importance is placed on developing the rigidity of such tooling.

Recent drill developments by Kennametal, shown at EMO 2007, illustrate the progress made.

* Drilling stainless steels - the KSEM-HPL(M) inserts have a patented geometry for Kennametal's modular KSEM solid-carbide drill.

Also the iKC7320 grade guarantees maximum process safety for drilling austenitic stainless steels and, at the same time, a low machining noise level.

Kennametal said that with cutting parameters often allowing double productivity, tool lives are achieved which are far in excess than com-parable tool lives of common solid-carbide or high speed steel (HSS) tools.

* New geometry - The HPL (M) geometry creates four individual chips, without front-face chip grooves.

This construction avoids chip jams because the four smaller chips are evacuated more quickly and more smoothly through the chip flutes than two big chips.

Unexpected tool breakage is practically excluded and even applications up to 10xD (D is hole diameter) are quite possible.

Noise levels are also greatly reduced.

The further development of the Kennametal HP-point, the HPL (M)-point can withstand feed rates far above those of competitors' tools even in tough work piece materials.

The new PVD-AITiN-coated grade KC7320, developed especially for the HPL(M)-point, increased cutting speeds and, at the same time, longer tool lives are additionally possible due to high temperature stability.

KenTIP-HPL(M) inserts can be used in existing KenTIP tool bodies and are designed for drilling applications in austenitic steels (cutting groups 14.1 and 14.2).

The main fields of application of the new geometry are in particular general mechanical engineering and energy generation.

Kennametal added that process safety, efficiency and long tool life are the outstanding features of this insert.

The company does not offer recycling of the insert as it would jeopardize its features.

* The 2x2 Double Ended Drill - the 2x2 Drill combines the application and performance characteristics of solid carbide drills with the commercial advantages of modular tools for drilling holes with diameters below 8.5mm.

The tool has similar performance parameters to Kennametal's solid carbide HP range of SE drills.

It allows cutting speeds of 150 to 200m/min in steel applications, which far exceeds the market standard for this type of tool, said the company.

Compared with conventional solid carbide drills, the tool life of the 2x2 Double ended Drill is typically four times higher.

The drill has two cutting ends rather than one.

A new coating on the drill gives it exceptional wear resistance delivering prolonged tool life.

When the first end of the drill is worn, simply turn the drill around and use the other end.

Kennametal said that thanks to the long tool life of the drill this feature typically saves two tool changes and also avoids expensive machine down time.

Kennametal classes the drill as an indexable tool and is not reground therefore only new consistent cutting edges are utilised, this promotes a high level of process security and repeatability.

* Steel and cast irons - The 2x2 Drill is designed for hole making in steel and cast iron components.

The range covers diameters from 3.1mm to 8.5mm and possible drilling depths of up to 7xD.

Special 2x2 Drill clamping sleeves are used to clamp the drill in a hydraulic expansion chuck, for excellent run out capability.

There are 12 clamping sleeves available in standard diameters and intermediate diameters (in steps of 0.001mm).

Plastics sealing caps are used to support the supply of internal coolant and also protect the non-cutting edge inside the chuck.

Once both ends of the 2x2 Drill have reached the end of their service life, it is simply replaced with a new drill giving consistent repeatable tool ,performance and length setting.

* Long drills used in wet and dry hole-making - Kennametal's B222HP solid carbide drill has been specifically designed for both wet and dry machining at drilling depths of 5xD.

The drill is designed for use in steel and cast irons.

The drill has the patented Kennametal HP point geometry allowing high penetration rates and increased productivity.

Productivity gains of up to and beyond 30% can be achieved, said Kennametal, increasing throughput and reducing manufacturing costs.

The drill is supplied in the Kennametal grade KC7315, which has a smooth multi layer TiAIN coating.

This smooth coating reduces built up edge and also promotes free flow of the chips away from the component.

It also ensures long predictable tool life even in the most demanding operations.

Such operating parameters are normally only associated with through coolant drills, claimed the company.

Kennametal also said that the high metal removal rates and ability to run dry could significantly impact in costs associated with cutting fluids and subsequent cleaning of components.

The B222HP in KC7315 is available from stock in cutting diameters from 3.0mm to 19.05mm with a form A cylindrical shank.

This range complements by the short version, the B221HP.

* Deep hole drill penetration rates increased by 100% - The Kennametal B27-Z-HPG increases penetration rates by 100% over gun and HSS drills in steel and iron applications up to 30xD deep.

The KC7425 grade, based on a sub-micron grade substrate, provides the durability and toughness required for deep hole applications in steel as well as cast and ductile iron.

Applications include automotive crankshafts, connecting rods, cylinder heads and blocks.

The drill features a flute profile that increases chip flow and reduces friction that would otherwise lead to chip jamming and catastrophic failure.

Kennametal said that the drills ensure drill stability in applications with cross-holes and irregular or angled exits.

The wear resistant coating and novel design makes the B27-HPG suitable for wet and minimum quantity lubricant applications.

The B27-HPG in KC7425 is available as a standard product from 3.0 to 10.0mm in 15xD and 20xD.

Customised drills are available in lengths greater than 20xD up to 30D.

* Drilling carbon-fibre reinforced polymers (CFRP) - Kennametal now offers a drill that produces a burr-free and delamination-free cutting process through out the entire tool life, while at the same time reducing costs.

The SPF drill is considered by Kennametal to be a real alternative to expensive PCD drills, in particular for CFRP materials drilled on CNC machines.

When compared with PCD drills, the SPF drill has double the life before any delaminations appear at the drill hole exit.

The smooth diamond coating on the SPF drill does not possess any metallic binder phases, resulting in increased wear resistance and reduced adhesion tendency, giving longer tool life and improved chip flow.

The material-specific front and chisel edge design gives increased self-centring capability and reduced feed forces, contributing to improved drill hole quality and less delamination, said Kennametal.

SPF drills are available as standard in diameter range from 0.098in to 0.500in, short (K531A) or long (K532A), and in the metric range from 3.2mm to 6.50mm short (B531A) and 5.1mm to 5.35mm long (B532A).

Other lengths and diameters are available.

The main applications of this novel tool lie in the Aerospace industry and its suppliers.

Machining should preferably be filled with extraction systems or flood coolant to evacuate any dust.

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