Drilling with a “Pagoda” in Croatia

Drilling soft steel is not as simple as it may seem.
The case study below shows how correct application of an innovative tool can significantly
improve performance in drilling operations. In our focus – Croatia.


Croatia… When speaking about this young state in the northwest Balkans, people usually mention the azure Adriatic Sea coast, the majestic Old City of Dubrovnik , the picturesque Plitvice Lakes, historical Zagreb, maybe the wonderful national football team that won many hearts in the last FIFA World Cup in Russia or even the fact that this country is the origin of neckties in Europe. Croatian beauty attracts people from all over the world, and tourism is a main national asset today. At the same time Croatia has a developed industry where machinery and metalworking play an important role. Many years of tradition, a skilled workforce, and international investment make the base of a promising outlook for the industry.
TPK OROMETAL‎, located not far from the Croatian capital Zagreb, is a company that specializes in manufacturing steam boilers, pressure tanks and vessels, and heat exchangers (Fig. 1). Founded in 1957, the company has a wealth of experience in producing pressure and non-pressure products, and has continuously adopted new technology methods. Today, TPK OROMETAL ‎ enjoys a well-deserved reputation as a reliable manufacturer of high-quality products.
Cooperation between TPK OROMETAL ‎ and ISCAR alati d.o.o., the subsidiary of ISCAR Ltd. in Croatia, began ten years ago. The relationship varied in intensity during this decade but both companies had enough time to assess the possibilities and prospects of collaborative work.
This relationship gained impetus when Tomislav Lisak, the machining production leader at TPK OROMETAL, was engaged in planning a new process to improve performance of drilling operations in manufacturing heat exchanger tube sheets (also referred to as heat exchanger plates or HEP). A tube sheet is generally a round plate with many holes - their number is in the hundreds or even thousands , depending on the dimensions of the heat exchanger. The holes are needed for locating and supporting pipes in the heat exchanger (Fig. 2). Low carbon steel is the most common material used in manufacturing the tube sheets.
The specific problem confronted by Tomislav Lisak related to drilling holes with a diameter d=18.3 mm in tube sheets made from steel DIN W.-Nr. 1.0478 with a hardness level of around HB 130. Machining a soft low carbon steel is not usually considered to be difficult. However, a significant drilling depth of 10×d - ten times larger than the hole diameter, combined with a high tool overhang and stickiness of the steel, presented obstacles to achieving the desired chip formation and tool life. This type of drilling operation is performed by a vertical machining center with the option of internal coolant supply under 12 bar pressure.
At the same time, Hrvoje Belov, a sales and application engineer from ISCAR alati d.o.o., presented a recent ISCAR development to the TPK OROMETAL management: the “SUMOCHAMIQ” family of HCP exchangeable carbide heads, which are intended for mounting in the bodies of standard SUMOCHAM drills. The “IQ” of the heads lies in its unusual pagoda form - a concave cutting edge profile (Fig. 3) whose shape substantially enhances the self-centering capability of the drill and enables drilling holes of depths up to 12×d directly into solid material, without pre-drilling a pilot hole. In addition, the HCP geometry facilitates gradual penetration into machined material which reduces the cutting forces, obtaining better hole quality – particularly when the drilling depth is significant.
Tomislav Lisak and Hrvoje Belov met and started to work together to resolve these issues, first by testing the new pagoda-shape heads and then by optimizing the cutting data, resulting in a tool life of 80 meters at a metal removal rate of 151 cm³/min (Fig. 4). This exceeded initial modest expectations: tool life was extended by 50% and the metal removal rate was increased to 28%. This data demonstrated outstanding benefits, especially when compared to results shown from testing a drill offered by another tool manufacturer.
Tomislav Lisak and Hrvoje Belov consider that this is just the beginning and that there are many collaborative tasks ahead - planning new processes, optimizing the existing ones, new tests, analysis, and more.
It was clear to all that when working together it is much easier and more effective to untie a tie of production problems, and that cooperation between customer and cutting tool producer should be close and collaborative to be fully effective. The ISCAR objective “To be your real partner in solving manufacturing tasks and not only a cutting tool supplier” represents a tried, tested and proven guide for achieving fruitful cooperation.

Tomislav Lisak:
“We work with ISCAR because they have a great tool that produces excellent results. Their sales network ensures delivery of over 90% of the tools within 24 hours, and their sales representative always find the best solution and tools to make the job we need to do.”

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