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Stable and high efficiency in small diameter deep-hole applications.

- Hiroyuki Amano, OSG Corporation Applications Engineer (Drill Development Division)

OSG Corporation has recently released the ADO-MICRO – the company’s first small diameter carbide drill with oil holes designed for stable and high efficiency drilling in deep-hole applications. The sense of size upon hearing the phrase “small diameter” will be understood differently among users in the manufacturing industry.

The ADO-MICRO has a lineup of drill diameters from 0.7 mm up to 2 mm for drill lengths of 2xD and 5xD, and diameter 1 mm to 2 mm for drill lengths of 12xD, 20xD and 30xD. The product name ADO-MICRO may seem to be associated with the unit prefix micro (µ), but it was named to simply imply smallness in size regardless of the unit.

For small diameter drilling, options such as carbide drills and HSS drills using external coolant are available. However, today’s machining needs require greater stability, higher efficiency and longer life than ever before. There is no exception in small diameter deep-hole applications, with growing needs for coolant-through small diameter drills.

Tool Geometry

One of the keys for successful small diameter drilling is trouble-free chip evacuation. As illustrated in figure 1, chips generated at the tip of the tool flow in the direction of the blue arrow. However, if there is insufficient space in the flute, cutting chips cannot evacuate smoothly, which causes the drilling accuracy to deteriorate and increases the probability of tool breakage. Therefore, by providing a wider flute specification at the area where the tip of the blue arrow locates, as depicted in figure 1, cutting chips are able to be discharged without difficulty, leading to stable machining.

Figure 1. Extended flute

In addition, the ADO-MICRO employs a unique double margin geometry (as depicted in figure 2) in all sizes to enable stable machining even in deep-hole applications. In order to ensure the rigidity of the cutting edge, the margin is set to the minimum necessary length. However, micro sludges can be easily accumulated around the outer periphery of the cutting tool, which is a key cause of abrupt tool breakage. To resolve this challenge and to achieve an overall balance, an extended flute configuration is incorporated to provide sufficient exit room as shown in figure 3.

Figure 2. Four support points with the double margin design

Figure 3. Exit room at end of margin

Oil Holes

The ADO-MICRO features a straight hollow shank design where coolant is injected in addition to the two spiral oil hole paths. This configuration increases coolant discharge from the tool tip. Without the hollow shank configuration, greater pressure is required in order for the coolant to pass through the thin oil hole paths. With the hollow shank feature, pressure loss is reduced, which increases the coolant flow volume. As illustrated in figure 4, with a higher coolant flow rate, cutting chips can be more effectively evacuated, thereby enabling stable machining.

Figure 4. Relationship between shank structure and coolant flow volume

OSG’s Latest Coating Technology: IchAda Coating

Another key element for achieving stable processing in small diameter deep-hole application is coating technology. The role of tool coating is to provide wear resistance and heat resistance to prolong tool life, which is particularly important to small diameter tooling. As illustrated in figure 5, the coating surface by conventional technology is not smooth, which may interfere with the performance of chip evacuation. OSG’s latest IchAda coating, on the other hand, provides excellent surface smoothness in conjunction with high wear resistance and heat resistance to enable small diameter tools to achieve long tool life by improving adhesion.

Figure 5. Surface of coating

Cutting Data

Figure 6 demonstrates a comparison of tool life between the ADO-MICRO and two other tooling manufacturers’ products in the machining of SCM440. The competitor drills have chipped or have broken at the initial machining stage. The ADO-MICRO, on the other hand, was able to achieve long tool life stably due to its superior chip evacuation capability by breaking chips into small and manageable pieces.

Figure 6. Stable and long tool life in SCM440

The ADO-MICRO demonstrates stable performance even in difficult-to-machine titanium alloy applications. As shown in figure 7, the competitor drill struggled with chip evacuation, thus requiring step processing. However, with the ADO-MICRO, step processing can be eliminated while achieving approximately five times the drilling efficiency. The ADO-MICRO was still in good shape after doubling the competitor drill’s tool life, allowing it to be used on other applications.

Figure 7. Efficiency improvement in titanium alloy

The ADO-MICRO’s unique tool geometry and OSG’s original IchAda coating allow non-step drilling even for deep-hole applications, enabling high processing efficiency. By eliminating common complication in small diameter deep-hole drilling, the ADO-MICRO is able to excel with stable performance in a wide range of work materials including stainless steel. In addition to standard stock items, OSG also offers customization services with tailored solutions for each and every manufacturer’s specific machining needs.

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