World's largest boring bar - Precision innovation

Sandvik Coromant has developed the world's largest boring bar. Measuring almost 11,000 mm (11 m) in length and 600 mm in diameter, it was developed specifically to meet the machining requirements of a Finnish engineering company.

The gargantuan lathe tool is going to be used to produce precise metal components for a range of sectors including offshore oil and gas, power transmission and renewable energy.

Häkkinen Group Jyväskylä unit had an unusual set of specifications. It needed a tool capable of machining a specific type of component with critical dimensions. Although the type of component was not specified – due to confidentiality agreements – it was especially large, measuring 800 mm in diameter by 12,000 mm (12 m) in length, and would be machined from both sides.

The required tool was a boring bar, used in machining operations to enlarge and refine the diameter of an existing hole in a workpiece. The holes made by a boring bar are more precise, accurate and smooth than those made by drilling, which may produce rougher holes.

However, the diameter and length of a boring bar is determined by the dimensions of the workpiece itself. It is recommended to select the largest possible bar diameter for an application to achieve the best possible stability. Put simply, the application required a boring bar of unprecedented dimensions. The large size would be essential to enable deep and precise internal turning operations, a task beyond the capability of standard-sized bars.

Häkkinen Group Jyväskylä unit approached its partner ŠMT – formerly Skoda Machine Tool – based in the Czech Rublic, one of the world’s leading producers of high-precision horizontal boring and milling machines, horizontal lathes and more. It was clear that ŠMT would need to enlist the services of a machine tooling specialist that could supply a boring bar with the extraordinary dimensions needed to accommodate the demands of such a unique project.

To this end, ŠMT turned to Sandvik Coromant in the Czech Republic, to ask if it could support with the development of the huge bar.

“Sandvik Coromant is renowned as a producer of boring bars, particularly bars with anti-vibrational qualities: Silent ToolsTM” explains Vaclav Faber, Project Engineer at Sandvik Coromant. “Reducing vibrations in a boring bar is crucial because it ensures precision and surface finish quality in machining operations.”

Excessive vibrations can lead to inaccuracies, tool wear and compromised workpiece integrity – which were concerns given the huge scale of the machining operation. Instead, by minimizing vibrations, the boring bar maintains stable and controlled cutting conditions, which results in higher productivity, extended tool life and superior surface finishes.

ŠMT had other stringent requirements for the bar: its customer, Häkkinen Group Jyväskylä unit, needed a tool that would integrate seamlessly with its existing machinery while pushing the boundaries of turning operations. It was also essential that the new bar be compatible for use in ŠMT’s huge lathe.

The bar is made of steel and contains a component called a "damper" made of heavy metal. A damper is a device used to reduce or absorb vibrations, rarely found in machinery or structures, and clamped in special rubber rings.

Another crucial feature of the bar is the Coromant Capto® tool holder affixed to in front of the bar, which would hold the cutting inserts needed to machine the workpiece. The Coromant Capto® is designed to reduce set-up and tool change times for significantly increased machine utilisation, and to support stable and reliable machining.

The tool holder has proven especially useful in multi-task machines.

“It enables assembling of tools with different lengths and design characteristics regardless of the machine interface. The Coromant Capto also meets Häkkinen Group Jyväskylä unit’s requirement for a boring bar that can be useable in a diverse range of industrial setups.”

Step forward Sandvik Coromant in Trondheim, Norway. The team was chosen for its reputation as a market leader in the development and production of boring bars that goes back to the 1960s.

Sandvik Coromant specialists conducted crucial frequency measurements on-site to assess the effectiveness of the dampening adapter integrated within the bar. The bar was put to work in a large CNC lathe and tested multiple times in three applications – roughing, finishing and profiling – each time with different cutting data.

“Based on the test results, Sandvik Coromant specialists were able to recommend cutting data parameters and inserts to ŠMT,” explains Faber.

The boring bar is remarkable for its size and is now being used in the Häkkinen Group Jyväskylä unit workshop to precision machine components for diverse sector. Going forward, and impressed by the world’s largest boring bar, ŠMT plans to invest in further – albeit slightly smaller – boring bars from Sandvik Coromant for the machining of slightly smaller components.

“The world’s largest boring bar remains testament to our unwavering commitment to innovation and precision and machining applications,” says Faber.

To learn more about Sandvik Coromant Silent ToolsTM boring bars, visit the website.