The GC4425 grade was subjected by Sandvik Coromant’s customers to pre-market tests. Among these was a general engineering company that applied both a competitor’s insert and the GC4425 insert, in the manufacture of pressure rollers. An ISO-P grade was subjected to continual external axial machining and semi-finishing at a cutting speed (vc) of 200 m/min, feed rate of 0.4 mm/rev (fn) and depth (ap) of 4 mm.

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Sandvik Coromant, part of the Sandvik group headquartered in Sandviken, Sweden, has announced that it is adding two new steel-turning carbide grades – GC4415 and GC4425 – to its range in an effort to improve cutting speeds and reduce energy consumption. Sandvik Coromant has reported that an average tool life increase of 25%, in combination with reliable and predictable performance can minimise materialise waste.

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The GC4425 grade reputedly provides extremely high process security through its ability to retain an intact edge line. Because the insert can deliver more pieces per edge, fewer carbides are consumed to machine the same number of components; consistence and predictability also help to minimise material waste.

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The company has stated that this illustrates the gains that can be achieved if the right machining elements are brought together. To help with process monitoring itself, Sandvik Coromant has also developed CoroPlus® Process Control software that can monitor machining in real-time and act according to programmed protocols if specific issues occur — for example, by stopping the machine or replacing a worn cutting tool.

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Largely driven by a trend to combine multiple subcontract operations into as fewer cycles as possible, deep hole drilling specialist Solutions reports. The trend is commensurate with the increased flexibility of CNC lathes, sliding head and turn/mill centres as well as vertical and horizontal machining centres where 60% of Mollart's tool sales are now directed. The growing trend away from the more conventional twist drills to solid carbide and indexable insert based ‘specialist' deep hole tools has been influenced by the adoption of through spindle, high pressure coolant supply options on new machines and the availability of retrofitted spray mist or high pressure systems on existing production equipment. To meet this need Mollart has recently invested in the development of its own HiCool 70 bar high pressure coolant system and a lower cost spray mist system. Both were developed against its 50 years of international success in the deep hole drilling market and its own subcontract production demands at Chessington, Surrey and Resolven in South Wales which often involves the deep hole drilling process. Says Chris Barker, director of Mollart Engineering and responsible for tooling: “A prime example of gundrilling being used to advantage on a turning centre by a subcontract customer in the north involved re-tooling a recently installed turn/mill centre to produce complex manifold blocks. It involved the combination of the previous independent gundrilling operation plus seven other production operations into a single cycle. The result was a massive reduction in leadtime and manpower plus the added bonus of improved levels of quality.” Dispelling misconceptions Key advantages of the gundrill, linked to production gains are its ability to consistently produce high tolerance, high quality, geometrically straight and round holes at high penetration rates in a component. Indeed, such is the performance increase from the latest HP Series of Botek gundrills from Mollart Engineering that penetration rates of the tool can be up to 800% greater than that achieved by a conventional drill. In addition, gundrills are now seen as being very competitive on price compared to standard long series or special carbide twist drills with further benefits generated when overall costs are taken into account such as higher machine utilisation and security of process. Also, due to the design of the gundrill, it can easily be specified to an exact length which has a distinct advantage in the compact working areas of CNC machining. “In the past gundrilling was often pigeon-holed as a highly specialised process requiring a dedicated machine, high volume production and for very deep holes over 10:1 length to diameter ratio in often difficult materials,” Mr Barker states, “However this is a misconception as the gundrilling process has become a highly viable solution and is even being used on holes of shorter depth.” Also growing in popularity on other machine types involving holes over 12mm diameter is Mollart's indexable insert range of deep hole drills. These have the added advantage of a simple insert change rather than having to remove a tool from the machine for regrinding point angles. Still critical in the deep hole process is coolant delivery and pressure plus the capability of the machine tool to have the axis travel to accommodate the tool length that may be required on deeper holes. Indeed, within Mollart Engineering's subcontract facilities in Chessington and Resolven, South Wales, seven Mazak Integrex turn/mill centres frequently incorporate gundrilling from solid for holes between 1.5mm and 100mm diameter. These holes are produced in parts requiring hole depths up to 770mm and quite often in difficult materials such as Inconel. Gundrill evolution There are two types of conventional gundrill – the single solid carbide tool for use in small diameter applications and the more traditional three piece type where a slug of carbide that forms the drill head and guide pads is brazed to a hollow vee-shaped tube that acts as ducting to carry the coolant feed through the drill tip to the cutting zone. However, in recent years tool development has progressed around the use of indexable carbide inserts for holes between 12mm and 100mm diameter which have added further advantages to the deep hole drilling process. As a result, regrinding of the drill point is not required enabling inserts to be changed quickly without removing the tool from the machine. It also provides a choice of chipbreaker form to best suit the material and the flexibility to upgrade and use higher performance coated inserts. In addition, the use of indexable inserts has added significant cost savings to the deep hole drilling process where larger diameter brazed tip ejector drills are normally utilised. Here, Mollart can now cost-effectively adapt and retrofit the indexable insert-based tooling as a package onto existing ejector drill-based tooling to enable these savings to be realised. Break it down Most critical in the gundrilling process is that swarf is broken down into small chips so they can be easily ejected via the coolant pressure from the cutting zone without jamming. Here the relationship between coolant pressure, flow, hole size and penetration rate of the tool is important. “This is why freely available application support and advice from an experienced tool supplier is critical to maximise the benefits of the process,” Mr Barker affirms. As part of Mollart's total package solution for deep hole drilling the company has developed its own compact HiCool 70 bar, 30 litres/minute high-pressure coolant system and a spray mist system. Both systems can be retrofitted to lathes and machining centres and the HiCool incorporates its own single or duplex paper filter elements at 15µm as standard or 5µm as an option. The system is compact requiring just 1m by 1.3m of floor area with simple connection to the machine tool. In operation, selected use can be made via an M-code and the tank contains 500 litres of either neat oil or water-based emulsion coolants. The low cost option of a spray mist system can also be retrofitted to any machine tool and is fed from a standard compressed airline at pressures up to 10 bar. The Mollart Spray Mist System is highly efficient for deep hole drilling holes between 5 and 25mm and up to 2,000mm deep. The air fed directly from a standard compressed airline passing through the system absorbs precisely timed pulsed jets of vegetable based cutting oil at up to 10 bar pressure from an integral reservoir. The oil is used to lubricate the drill tip and guide pads preventing seizure in the hole while the air purge effectively cools the cutting tool and pads while pressurising the chipped swarf back down the vee groove between the outside of the tool tube and the drilled hole. So efficient is this action that if the gundrill is removed from the component, it will be immediately cool to the touch. For smaller holes air and coolant pressure needs to be higher, however, as the hole becomes larger in diameter, volume and flow become more important. The hole picture To produce the gundrilled hole on a dedicated gundrilling machine, the tool is able to cut directly from solid by using a sized guide bush against the start point. On a lathe or machining centre the guide bush is replaced with a start hole normally created by a conventional drill 0.02mm larger than the diameter of the gundrill. The pilot start hole only has to be drilled to a depth of two to three times the diameter of the hole. The gundrill is then fed into the start hole, coolant pressure applied and the tool or workpiece rotated up to the required cutting speed and the rate of feed engaged. Once the drilled depth is achieved at a single stroke, unlike conventional twist drills where pecking cycles are mostly required to clear swarf, the gundrill is returned at rapid traverse to the pilot hole position, the coolant and spindle rotation stopped and the tool withdrawn. As Mr Barker points out, the solid carbide tip of the gundrill is fully supported in the hole by the guide pads that also burnish the surface to high orders of finish. Mollart www.mollart.com

Manufacturers typically measure tool life by the number of workpieces machined. While competitor’s grade machined a reported twelve pieces before wearing out due to plastic deformation, Sandvik Coromant’s insert produced eighteen pieces and, in doing so, worked 50% longer with stable and predictable wear.

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GC4425 is said to deliver improved wear resistance, heat resistance and toughness, while grade GC4415 is designed to complement GC4425 when enhanced performance and more heat resistance is needed. Both grades are suitable for use with tough materials like Inconel and unalloyed stainless steel ISO-P grades that are complex and difficult to machine.

Extensive Powder Metallurgy industry news coverage, and the following exclusive deep-dive articles and reports:

With both GC4425 and GC4415, the insert’s substrate and coating have been developed to better withstand high temperatures. Both contain a second-generation Inveio® layer, a textured chemical vapour deposition (CVD) alumina (Al2O3) coating developed for machining. Inveio creates a strong barrier towards the cutting zone and extends the life and wear resistance of tools.

Largely driven by a trend to combine multiple subcontract operations into as fewer cycles as possible, deep hole drilling specialist Solutions reports. The trend is commensurate with the increased flexibility of CNC lathes, sliding head and turn/mill centres as well as vertical and horizontal machining centres where 60% of Mollart's tool sales are now directed. The growing trend away from the more conventional twist drills to solid carbide and indexable insert based ‘specialist' deep hole tools has been influenced by the adoption of through spindle, high pressure coolant supply options on new machines and the availability of retrofitted spray mist or high pressure systems on existing production equipment. To meet this need Mollart has recently invested in the development of its own HiCool 70 bar high pressure coolant system and a lower cost spray mist system. Both were developed against its 50 years of international success in the deep hole drilling market and its own subcontract production demands at Chessington, Surrey and Resolven in South Wales which often involves the deep hole drilling process. Says Chris Barker, director of Mollart Engineering and responsible for tooling: “A prime example of gundrilling being used to advantage on a turning centre by a subcontract customer in the north involved re-tooling a recently installed turn/mill centre to produce complex manifold blocks. It involved the combination of the previous independent gundrilling operation plus seven other production operations into a single cycle. The result was a massive reduction in leadtime and manpower plus the added bonus of improved levels of quality.” Dispelling misconceptions Key advantages of the gundrill, linked to production gains are its ability to consistently produce high tolerance, high quality, geometrically straight and round holes at high penetration rates in a component. Indeed, such is the performance increase from the latest HP Series of Botek gundrills from Mollart Engineering that penetration rates of the tool can be up to 800% greater than that achieved by a conventional drill. In addition, gundrills are now seen as being very competitive on price compared to standard long series or special carbide twist drills with further benefits generated when overall costs are taken into account such as higher machine utilisation and security of process. Also, due to the design of the gundrill, it can easily be specified to an exact length which has a distinct advantage in the compact working areas of CNC machining. “In the past gundrilling was often pigeon-holed as a highly specialised process requiring a dedicated machine, high volume production and for very deep holes over 10:1 length to diameter ratio in often difficult materials,” Mr Barker states, “However this is a misconception as the gundrilling process has become a highly viable solution and is even being used on holes of shorter depth.” Also growing in popularity on other machine types involving holes over 12mm diameter is Mollart's indexable insert range of deep hole drills. These have the added advantage of a simple insert change rather than having to remove a tool from the machine for regrinding point angles. Still critical in the deep hole process is coolant delivery and pressure plus the capability of the machine tool to have the axis travel to accommodate the tool length that may be required on deeper holes. Indeed, within Mollart Engineering's subcontract facilities in Chessington and Resolven, South Wales, seven Mazak Integrex turn/mill centres frequently incorporate gundrilling from solid for holes between 1.5mm and 100mm diameter. These holes are produced in parts requiring hole depths up to 770mm and quite often in difficult materials such as Inconel. Gundrill evolution There are two types of conventional gundrill – the single solid carbide tool for use in small diameter applications and the more traditional three piece type where a slug of carbide that forms the drill head and guide pads is brazed to a hollow vee-shaped tube that acts as ducting to carry the coolant feed through the drill tip to the cutting zone. However, in recent years tool development has progressed around the use of indexable carbide inserts for holes between 12mm and 100mm diameter which have added further advantages to the deep hole drilling process. As a result, regrinding of the drill point is not required enabling inserts to be changed quickly without removing the tool from the machine. It also provides a choice of chipbreaker form to best suit the material and the flexibility to upgrade and use higher performance coated inserts. In addition, the use of indexable inserts has added significant cost savings to the deep hole drilling process where larger diameter brazed tip ejector drills are normally utilised. Here, Mollart can now cost-effectively adapt and retrofit the indexable insert-based tooling as a package onto existing ejector drill-based tooling to enable these savings to be realised. Break it down Most critical in the gundrilling process is that swarf is broken down into small chips so they can be easily ejected via the coolant pressure from the cutting zone without jamming. Here the relationship between coolant pressure, flow, hole size and penetration rate of the tool is important. “This is why freely available application support and advice from an experienced tool supplier is critical to maximise the benefits of the process,” Mr Barker affirms. As part of Mollart's total package solution for deep hole drilling the company has developed its own compact HiCool 70 bar, 30 litres/minute high-pressure coolant system and a spray mist system. Both systems can be retrofitted to lathes and machining centres and the HiCool incorporates its own single or duplex paper filter elements at 15µm as standard or 5µm as an option. The system is compact requiring just 1m by 1.3m of floor area with simple connection to the machine tool. In operation, selected use can be made via an M-code and the tank contains 500 litres of either neat oil or water-based emulsion coolants. The low cost option of a spray mist system can also be retrofitted to any machine tool and is fed from a standard compressed airline at pressures up to 10 bar. The Mollart Spray Mist System is highly efficient for deep hole drilling holes between 5 and 25mm and up to 2,000mm deep. The air fed directly from a standard compressed airline passing through the system absorbs precisely timed pulsed jets of vegetable based cutting oil at up to 10 bar pressure from an integral reservoir. The oil is used to lubricate the drill tip and guide pads preventing seizure in the hole while the air purge effectively cools the cutting tool and pads while pressurising the chipped swarf back down the vee groove between the outside of the tool tube and the drilled hole. So efficient is this action that if the gundrill is removed from the component, it will be immediately cool to the touch. For smaller holes air and coolant pressure needs to be higher, however, as the hole becomes larger in diameter, volume and flow become more important. The hole picture To produce the gundrilled hole on a dedicated gundrilling machine, the tool is able to cut directly from solid by using a sized guide bush against the start point. On a lathe or machining centre the guide bush is replaced with a start hole normally created by a conventional drill 0.02mm larger than the diameter of the gundrill. The pilot start hole only has to be drilled to a depth of two to three times the diameter of the hole. The gundrill is then fed into the start hole, coolant pressure applied and the tool or workpiece rotated up to the required cutting speed and the rate of feed engaged. Once the drilled depth is achieved at a single stroke, unlike conventional twist drills where pecking cycles are mostly required to clear swarf, the gundrill is returned at rapid traverse to the pilot hole position, the coolant and spindle rotation stopped and the tool withdrawn. As Mr Barker points out, the solid carbide tip of the gundrill is fully supported in the hole by the guide pads that also burnish the surface to high orders of finish. Mollart www.mollart.com

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