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ATI Stellram will unveil its strategy for thin-wall machining of titanium components at the AeroEngineering Show in Manchester from 10-11 November.

The solution provider for difficult-to-machine materials has developed the 8:1 rule, following a programme of testing undertaken by its research team in the US in conjunction with a top aircraft manufacturer.

ATI Stellram’s trials have shown that optimum cutting conditions can be achieved through the combination of a strength ratio of height to width of 8:1 and the application of a variable cutting edge.

‘A wall that is 100mm high needs a minimum width of 12.5mm to support it while machining takes place as any smaller width weakens the wall’s strength and creates unstable cutting conditions,’ said John Palmer, ATI Stellram’s global aerospace manager.

‘The rule, in addition to adhering to the machining steps of roughing, qualifying and finishing, is easy to prove on a profiling application using a standard four-flute end milling cutter to create a thin wall by reducing the width on successive small radial passes.

Providing the cutter is sharp and the speed and feed is correct, the wall will become unstable once the 8:1 ratio is achieved, whatever the axial depth of cut.

He added: ‘For example, a 25mm diameter end milling cutter, machining a 24mm-high wall in successive 0.5mm radial depths of cut, will successfully reduce the wall to 3mm before problems such as deflection and harmonics arise.’ ATI Stellram will also show a variety of cutting tool programmes designed for use on difficult to machine materials.

These include the solid-carbide RSM programme, which has been specifically launched for the machining of titanium air frames.

ATI Stellram develops and produces high-performance cutting tools for difficult-to-machine materials used in a wide variety of industries including aerospace, power generation, medical, oil and gas production as well as automotive.


Its extensive product range comprises inserts and toolholders suitable for applications in drilling, grooving, milling, threading and turning.In addition ATI Stellram develops new grades and specialist combinations of substrates and coatings. Renowned for solving hard machining challenges, ATI Stellram has also established a reputation for developing innovative solutions designed to deliver better productivity, lower costs and higher quality, especially for the new generation of materials like nickel-, cobalt- and titanium-based alloys. ATI Stellram is a business unit of ATI Engineered Products and part of the ATI Aerospace team, a group of global businesses that produce a wide range of specialty metals and cutting tool solutions.


It has manufacturing facilities in the UK, Switzerland and the United States, and 9 sales offices around the world. ATI Stellram’s tooling engineers and metallurgists work closely with other specialists within the group to develop smarter solutions for difficult-to-machine materials.


This seamless technology transfer between the ATI companies provides an extensive knowledge base, not only of specialty metals, but also cutting tool performance.

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