Small Diameter Deep-hole Drilling

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ADO-MICRO coolant-through carbide drill boosts productivity and eliminates tool breakage in military aircraft engine part production

Hao Tian | OSG Shanghai

Deep-hole drilling has always been a challenging process for manufacturers. Small diameter deep-hole machining presents even greater difficulties due to various dimensional constraints. Generally speaking, if the depth of hole is five times or more than the drill diameter, it can be considered as deep-hole drilling. Manufacturing technologies and requirements are constantly evolving. Criteria such as efficiency, stability and hole accuracy have become increasing demanding. Performance requirements for small diameter deep-hole drilling is no exception.

Common Machining Challenges of Small Diameter Deep-hole Drilling

1. Chip evacuation

2. Straightness of hole

3. Cutting heat

4. Hole surface roughness

Chip evacuation is one of the most common difficulties presented in small diameter deep-hole drilling as the machine operator is unable to observe chip removal in time. The second challenge of small diameter deep-hole drilling is processing direction. Due to the long depth, it is difficult to confirm whether or not the processing direction is straight, and deviation is prone to occur. The third challenge is cutting heat. If the machine coolant does not reach the part being processed, cutting heat cannot be released in time, which reduces tool life. Last but not least, the extra friction of the tool and debris will make the surface roughness of the finished hole difficult to guarantee.

In order to resolve the above common challenges, 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 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. The flow volume per minute of the ADO-MICRO is estimated to be three to four times versus traditional drill hole design. The ADO-MICRO’s unique flute geometry enables outstanding chip evacuation performance and avoids sudden breakage of the tool due to poor chip removal. Additionally, its double margin configuration supports the straightness stability of the tool and guarantees the verticality of the machined hole. Moreover, with the addition of OSG’s original IchAda coating, excellent surface smoothness in conjunction with high abrasion resistance and heat resistance can be achieved to enable long tool life even in small diameter deep-hole processing. Manufactures from industries such as automotive, 5G, gear and shaft processing can especially benefit from the ADO-MICRO’s superior capability in small diameter deep-hole applications.

The ADO-MICRO small diameter coolant-through carbide drill is suitable for carbon steel, alloy steel, stainless steel, cast iron, ductile cast iron, aluminum alloy, titanium alloy and heat resistant alloy. The ADO-MICRO is available from diameter 0.7 mm up to 2 mm for drill lengths 2xD and 5xD, and diameter 1 mm to 2 mm for drill lengths 12xD, 20xD and 30xD.

Recently, a military industrial company located in Guangzhou, China, whose name cannot be disclosed due to confidentiality reasons, is able to leverage the ADO-MICRO in its military aircraft engine part production.

Made of superalloy GH5188 (HAYNES 188), each part requires the processing of 72 blind holes at a diameter of 1.6 mm and a depth of 16 mm. The parts are processed using a DMG DMU 80P 5-axis vertical machining center (BT40). This end user was originally using carbide drills without oil holes mainly by domestic cutting tool manufacturers in China. However, the client was dissatisfied with the processing efficiency and tool life due to poor chip evacuation and tool breakage. In terms of cutting parameter, the end user was originally processing the parts by step drilling at 0.4 mm step, a cutting speed of 900 min-1 and a feed rate of 11 mm/min with external coolant.

For small diameter deep-hole drilling, manufacturers would often opt for gun drills or conventional drills to reduce cost. However, the processing efficiency of these options is very low, making them an unrealistic solution for mass production. Seeking to improve performance, this manufacturer came in contact with OSG Shanghai through a distributor. Based on the requirements of the end user, OSG recommended the ADO-MICRO (EDP# 8732041) for cutting trial.

The ADO-MICRO demonstrates stable performance and eliminates the headache of tool breakage in military aircraft engine part production made of superalloy GH5188 (HAYNES 188).

The ADO-MICRO is able to process at a cutting speed of 12 m/min, a rotating speed of 2,400 rpm, a feed rate of 29 mm/min and increase seven times the step to 2.8 mm. Water-soluble coolant is also applied. The judgement for success is to complete a unit with a total of 72 holes. The ADO-MICRO reached the initial objective at ease and could continue to be used. Ultimately, the ADO-MICRO is able to achieve more than five times the processing efficiency versus the previous tooling choice with far greater tool life. By implementing OSG’s ADO-MICRO, this client is able to achieve stable small diameter deep-hole drilling performance and eliminate the headache of tool breakage.

For more information on the ADO-MICRO small diameter coolant-through carbide drill series