LMT Onsrud is specialised in solid carbide mills for high-speed manufacturing of aluminium, composites and plastics.

Fiber-reinforced composites are making today’s aircraft lighter and lighter, but at the same time presenting serious challenges for industrial production. Whereas in 1974 the proportion of carbon-fiber reinforced plastics, or CFRP, in the Airbus A300 was only 4%, composite materials make up over 50% of the new models by the world’s two largest aircraft manufacturers, the Airbus A350 and the Boeing 787. LMT Onsrud has played an active part in this development from the very start. Based in Waukegan near Chicago, today the US tool manufacturer is the competence center for composite materials within LMT Tools.

Experts for Special Materials

How do you guarantee the highest possible level of process reliability while drilling 470 holes in a sensitive titanium component worth over 80,000 dollars? This is typical of the kind of challenge that a medical technology company presents LMT Onsrud. The Waukegan-based company has specialized in high-value tools for the machining of unusual materials.

The company’s origins go back to 1912 when Oscar Onsrud opened a tool store in Chicago. He managed to gain a foothold in the aviation industry with a manually controlled pneumatic cutter. The tool store eventually became the Onsrud Machine Company, manufacturing equipment and tools for the machining of wood and non-ferrous metals. In 1946 tool production was separated off and became Onsrud Cutter, a new company based in Libertyville. In 1999 Onsrud became part of LMT.

The Challenge of Composites

From the very outset the company made a name for itself in the aviation industry and among wood-processing firms due to the high quality of its tools and its delivery reliability. In the early 1980s, when the furniture industry first relocated to Mexico before then moving to Asia, LMT Onsrud entered new markets, such as medical technology and the leisure industry, which involved the cutting of new and demanding materials.

Following this change of direction, tool development at LMT Onsrud began to focus on specialized materials. The share not only of fiber-reinforced composites, but also honeycomb materials increased dramatically, above all in the aerospace industry. These materials combine maximum strength with low weight. However, machining them is difficult. As a result, LMT Onsrud specially designed a tool to meet these requirements, the DFC Compression Mill. Its cutting geometry combines an upcut and downcut so that the tool presses the individual CFRP layers together, thereby preventing delamination.

Tools for the machining of composite materials also play a central role in LMT Onsrud's strategy. One of its latest developments is a tool for the high-speed milling of composites. Instead of grinding, the mill cuts the material, creating chips that dissipate the heat as they are removed. That leads to longer tool life and smoother edges. In addition to pure CFRP, increasing use is now being made of so-called stacks, which consist of alternating layers of CFRP materials and metals like aluminium. Here LMT Onsrud can combine its knowledge of the machining of CFRP and metals, which it has acquired through close cooperation with LMT USA. Today cutting tools for aluminium and other light metals account for roughly 15% of sales – and are experiencing double-digit growth.