“There are companies that require face grooves with major diameters as small as 0.2 mm,” says Duane Drape, national sales manager for Horn USA Inc., in Franklin, TN. “This is mostly aluminium, but I have had customer requirements to get that small with steel at 50 + Rockwell.”

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“You need the chips to be able to freely get out of the bore and away from the cutting action so they do not interfere with the machining process.”

Carbide insert and cutting tool manufacturer Horn reports that an application at Jörg Bamann Mechanische Werkstatt – a job shop in Geretsried, Germany – is demonstrating that a Horn DAH high-feed, indexable-insert milling cutter in a B-axis lathe is able to helically interpolate a circular groove into a round steel workpiece 14 times faster than a toroidal mill.

“It would be preferable to take an indexable insert into small grooves, because it would be more economical. But you often have to go with a one piece design, using a brace tool with a carbide or carbon steel cutter brazed to it.”

“It is important to keep speeds as low as possible when you have small-sized parts,” says Igor Kaufmann, a member of Kennametal Inc.’s global team for turning tools. When grooving miniature parts, Kaufmann emphasizes that the tools still need to fit axially and apply radial force to the bore. As a result, it is hard to ensure that the tool is strong enough, which then leads not only to chatter issues but also challenges with breakage and chip evacuation.

When grooving small pieces, cutting pressure tends to be relatively high. Aside from slowing feed rates, it can also help to use high lubricity coolants that work well in tight spaces.

“This is a double-sided insert that works well with slow cutting forces,” says Kaufmann. “The GUP insert geometry is advanced and versatile, with excellent metal removing rates.”

ID grooving in particular can be an issue with small parts, says Steve Geisel, senior product manager for Iscar Tools Inc., Oakville, ON.

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But replaceable inserts, single edge, can still get to some small diameters. More cost effective than a solid carbide tool, they can also deliver better axial depth. That said, solid carbide tools are usually more expensive, toolholders aren’t, and there is a risk the holder might break after a dozen or so uses.

“The grades Iscar uses for our inserts depend on how fast the machine spindle can spin,” says Iscar Tool’s Geisel. “10,000 rpm sounds high but remember you are working with very small parts, around .100 in. in diameter. So that 10,000 rpm with a .100 in. diameter works out to be about 260 sfm…we need to design and produce the insert out of carbide grades with coatings that can run at such speeds.”

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If the chip created by the grooving tooth is wider than the finished groove, then you can minimize the possibility that the chip will stay in the groove. But when it comes to harder metals the challenge isn’t chip control so much as creating the chip in the first place. “At 1.5 mm you need to have a tool that is strong enough to create the chip,” says Stewart. “But from there, with a strong alloy like Inconel, it is relatively easy to control the chip. In the case of aluminium and softer materials, where the chip is continuous, it creates greater headaches because the material balls up.”

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A frequent issue is whether or not to go with inserts or solid carbide tools. Inserts can be indexable or have only one edge for single use. Inserts tend to be less expensive, but usually can’t get into the smallest bores, and are not as strong as solid-carbide tools.

Carbide insert and cutting tool manufacturer Horn reports that an application at Jörg Bamann Mechanische Werkstatt – a job shop in Geretsried, Germany – is demonstrating that a Horn DAH high-feed, indexable-insert milling cutter in a B-axis lathe is able to helically interpolate a circular groove into a round steel workpiece 14 times faster than a toroidal mill. The 42CrMo4 (1.7225) alloy steel billet, quenched and tempered to 1,000N/mm², requires a 40mm wide groove having a 240mm outside diameter and a depth of just less than 90mm to be rough-machined. The component is a key part of a hydraulic rotator, used in the construction and forestry industries for rotating attachments carried by excavators. Seeking to optimise the groove machining process, owner Jörg Bamann approached Horn application engineer Korbinian Niedermeier, who recommended a high-feed milling solution. The subcontractor has been using Horn products for two decades, so knows the supplier well. Jörg Bamann (right) with Horn application engineer Korbinian Niedermeier Mr Bamaan says: “Before switching to milling, we tried to produce the recess in the component by axial turning, but it didn’t prove to be viable. We tried tool solutions from various manufacturers, but none of them had the technical capabilities we needed. Turning resulted in long chips and, due to the large groove depth, caused vibration that negatively affected the life of the inserts.” Next, the subcontractor tried replacing the turning tool with a conventional, 5-flute, toroidal milling cutter with indexable inserts in the B-axis tool spindle of a DMG Mori CTX 800 TC turning-milling centre. The roughing process was faster than axial turning but resulted in vibration and a high level of noise. Furthermore, the machining time was still too long for Mr Bamann. About 100 minutes were needed to produce the groove and each cutter was able to complete only 30 components before the inserts needed to be changed, so further process optimisation was called for. Mr Niedermeier proposed a 40mm diameter, high-feed DAH mill with five triple-edged inserts. At a cutting speed (vc) of 150m/minute, the tool is helically interpolated into the rotating workpiece with a continuous infeed depth (ap) of 1mm and 0.8mm feed per tooth (fz). The new machining time for the recess is now just seven minutes per component, more than 14 times faster, and the life of the indexable inserts has increased threefold to 90 components per edge. Mr Bamann affirms: “We are very happy with the result. Using the high-feed milling cutter has reduced the cycle time considerably and the load on the machine has also decreased, as cutting pressure and vibration are lower. There is still more potential for machining improvement.” Established in 1964 and now in its second generation of ownership, Jörg Bamann Mechanische Werkstatt CNC mills and turns parts for customers in a variety of industries in batch sizes ranging from one-offs to series production. The company's many years of experience in processing steels including stainless, aluminium alloys, non-ferrous metals, titanium and plastics are testament to its expertise and versatility. The use of modern CAD/CAM systems enables components to be machined quickly and cost-effectively to meet customer requirements. Horn Cutting Toolswww.phorn.co.uk

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Mr Bamaan says: “Before switching to milling, we tried to produce the recess in the component by axial turning, but it didn’t prove to be viable. We tried tool solutions from various manufacturers, but none of them had the technical capabilities we needed. Turning resulted in long chips and, due to the large groove depth, caused vibration that negatively affected the life of the inserts.”

Hydraulics, given their need to control pressure, create demand for inside diameter (ID) and outside diameter (OD) grooving seals and threads, as well as relief grooves. In the automotive sector, miniature grooving applications include fittings for air bags and fuel injection components.

“The challenge with grooving is that below 1.5 mm it is difficult to make a tool that is strong enough,” says John Stewart, VP of engineering at Bokum Tool in Madison Heights, MI. “The overall determining factor is: What does a groove look like in a hole that size? If it is proportionally very similar to a larger hole then it is theoretically possible to get very small, but it really comes down to the strength of the tool itself.”

The company's many years of experience in processing steels including stainless, aluminium alloys, non-ferrous metals, titanium and plastics are testament to its expertise and versatility. The use of modern CAD/CAM systems enables components to be machined quickly and cost-effectively to meet customer requirements.

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TW Ward CNC Machinery (Ward CNC) is pleased to announce that Andrew Elliott has rejoined the company in the sales department and senior management team.

Established in 1964 and now in its second generation of ownership, Jörg Bamann Mechanische Werkstatt CNC mills and turns parts for customers in a variety of industries in batch sizes ranging from one-offs to series production.

Manufacturers face an age-old paradox: manufacturing efficiency versus quality. After all, higher efficiency risks compromising quality while focusing on quality can reduce productivity – and this dilemma is becoming more challenging.

From 30-31 October, ITC will again be exhibiting at the Advanced Engineering Exhibition on Stand T171 in Hall 3 at the NEC Birmingham.

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“The cutting process produces pressure on the work piece and on the tool. Controlling the pressure during machining dictates how successful we will be [in producing an effective cutting tool]. We can control cutting pressures by controlling the width of the grooving insert; the wider the insert, the more pressure it will produce. We also grind positive rakes on the inserts to control the pressure and to act as a chip former to control the chip shape and size.”

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“Slow feeds can be a good idea, depending on the material,” says Bokum Tool’s Stewart. “With smaller sizes a weaker tool neck will want to deflect, especially with carbide, and with increased distance to the groove, feed speeds need to be adjusted downward.”

Tooling manufacturer Horn has introduced a new carbide insert grade, SG66, for turning components from steel that has been case hardened to 58 HRC. Due to the high flexural strength of the carbide substrate, the insert is also suitable for interrupted cutting.

“The geometries are not standardized, but there are ways to create space at the head of the tool to promote chip flow,” says Stewart. “Sometimes the actual grooving tooth on the cutting tool will have a chip breaker on it—this will help the chip move out and get flushed with coolant.”

“As a tooling manufacturer, we are being pushed to produce tooling able to groove in smaller, and smaller diameters. Our PICCO line can produce grooves in diameters from as small as 2 mm (.08 in.) and we can go smaller by special request.”

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Next, the subcontractor tried replacing the turning tool with a conventional, 5-flute, toroidal milling cutter with indexable inserts in the B-axis tool spindle of a DMG Mori CTX 800 TC turning-milling centre. The roughing process was faster than axial turning but resulted in vibration and a high level of noise. Furthermore, the machining time was still too long for Mr Bamann. About 100 minutes were needed to produce the groove and each cutter was able to complete only 30 components before the inserts needed to be changed, so further process optimisation was called for.

Manufacturers face an age-old paradox: manufacturing efficiency versus quality. After all, higher efficiency risks compromising quality while focusing on quality can reduce productivity – and this dilemma is becoming more challenging.

“Exotic materials are not for production jobs—these are low volume applications,” says Tom Ficker, regional sales manager for Cogsdill Tool Products, Inc., with responsibility for Canada. “The problem with precision grooving in high nickel alloys is that you beat down on the grooving insert almost from the get-go.”

As a result, Cogsdill’s tools are better suited to high production lines, an area that has seen some big changes of late. Only a few years ago, small bores were typically 4 mm, but now leading vendors are delivering off-the-shelf bore grooves to 2 mm, with specialty applications going much smaller. This has resulted in new abilities—and challenges—when it comes to grooving very small parts, as well as increased demand.

Mr Bamann affirms: “We are very happy with the result. Using the high-feed milling cutter has reduced the cycle time considerably and the load on the machine has also decreased, as cutting pressure and vibration are lower. There is still more potential for machining improvement.”

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Mr Niedermeier proposed a 40mm diameter, high-feed DAH mill with five triple-edged inserts. At a cutting speed (vc) of 150m/minute, the tool is helically interpolated into the rotating workpiece with a continuous infeed depth (ap) of 1mm and 0.8mm feed per tooth (fz). The new machining time for the recess is now just seven minutes per component, more than 14 times faster, and the life of the indexable inserts has increased threefold to 90 components per edge.

Geisel concurs with John Stewart that the challenge for tooling suppliers is to make a strong, rigid cutting tool or insert.

Managing chip generation in tight spaces has always been a challenge, because the smaller the hole the harder it is to get the chip out. One approach is to plum or port the tool to get coolant out. There are also advanced tools, like Kennametal’s AF-GUP insert geometry for grooving and turning, that are specially designed for these challenges.

Seeking to optimise the groove machining process, owner Jörg Bamann approached Horn application engineer Korbinian Niedermeier, who recommended a high-feed milling solution. The subcontractor has been using Horn products for two decades, so knows the supplier well.

The 42CrMo4 (1.7225) alloy steel billet, quenched and tempered to 1,000N/mm², requires a 40mm wide groove having a 240mm outside diameter and a depth of just less than 90mm to be rough-machined. The component is a key part of a hydraulic rotator, used in the construction and forestry industries for rotating attachments carried by excavators.

“If you are cutting to small major diameters on the face, where the grooves generally aren’t that deep, the chips are not an issue,” says Drape. “But in ID grooving applications where the groove is deep into a bore, then we need to get coolant in, and also need to break down the chip so it can evacuate.”

How best to approach grooving a small part has a lot to do with the materials involved: repeat, high volume applications tend to be with softer metals, with specialty one-offs applying to higher value applications, often with tougher alloys.

Another approach is to compress chip width, thus ensuring it doesn’t lodge in the groove and result in tool failure. Either way, when it comes to grooving small parts, the combination of slow feed rates, proper tool selection, and a strategy for chip evacuation is the best way to ensure success.

Solid carbide grooving tools are usually L-shaped. Part of the challenge is that even the non-cutting, or “leg” part has to fit into the bore diameter. Given that the bottom of the L, or the “foot” has to be even smaller, strength becomes an issue, as does the fact that groove depth is limited. As a result, with bores of less than 2 mm in diameter the best tools are now constrained to a groove depth of around 0.2 mm.

The problem with carbide is that reducing deflection increases the risk a tool will break, so it’s important to preserve the strength of the neck of the tool. Tool monitoring is also recommended, because with small cutting edges it can be hard to see or hear when a tool breaks.

Tooling manufacturer Horn has introduced a new carbide insert grade, SG66, for turning components from steel that has been case hardened to 58 HRC. Due to the high flexural strength of the carbide substrate, the insert is also suitable for interrupted cutting.