Iscar: introduced the Multi-Master family of rotating cutting tools with interchangeable solid-carbide heads in 2000. These tools now have a strong presence in the manufacturing industry and are widely accepted by metalworking specialists. To explain the line’s capabilities, Iscar has prepared an informative question-and-answer session.

The Multi-Master design features a solid-carbide head connected with the tool body (shank) via a specially shaped thread. The thread connection, being successfully produced directly on a solid-carbide part, changed preexisting views regarding such an approach and motivated other cutting-tool producers to create similar systems.

In Multi-Master, one shank can carry heads of various cutting shapes. This maximizes the family’s versatility and functionality, significantly decreases the need for specially tailored tools, and enables users to reduce tool inventory. A few combinations of Multi-Master heads and shanks produce a great variety of cutting tools that meet exacting performance requirements and ensure reductions in production and logistical costs. Unlike with regular solid tools, regrinding is unnecessary, and tungsten carbide consumption is lessened.

The following Q&A presents questions new Multi-Master users typically ask, with answers that make clear the technological advantages this tool family offers.

How is a head mounted into a shank? A head has two surfaces: a short taper and a rear noncutting face that determines the head location in a shank. The taper ensures high concentricity, and the face a face contact. The thread is intended for securing the head. Therefore the rear (tail) part of the head has two areas: tapered and threaded.

During mounting, the head is initially rotated by hand and then tightened by means of a key. The head has flats for applying a key.

What are the advantages of the face contact? First, the face contact considerably increases both the stiffness of an assembled tool and its ability to withstand impact loading. This factor allows for stable cutting, minimizes vibrations and reduces power consumption.

Second, the face contact ensures high repeatability of the head overhang with respect to the shank. As a result, no additional adjustment is necessary after a head is replaced. An operator can change the head without removing the shank from a machine tool spindle.

What is meant by the “initial gap”? When tightening a head, an operator first rotates the head by hand. The head stops rotating at some point, and a small gap remains between the contact faces of the head and the shank. This important “initial” gap measures several tenths of a millimetre, the exact value depending on the thread size. Further head tightening is possible only with the use of the key. Tightening of the head causes elastic deformation, in a radial direction, of the contact area of the shank section.

Why is behind the Multi-Master thread’s special profile? Multi-Master heads are produced from tungsten carbide, an extremely hard heat-resistant material that exhibits lowered impact strength against certain workpiece materials, as, for example, high-speed steel (HSS). One of the main problems to be solved in designing a threaded tungsten carbide part thus is to minimize stress concentrators.

Additionally, the Multi-Master thread connection is relatively small, with nominal thread diameters generally between 5 and 15 mm. These sizes, along with the need to meet strength requirements for operational loads, can limit the height of the thread profile.

Therefore, using the standard threads would be problematic. A special thread shape that will comply with specifications of the connection was clearly necessary, and that is why Iscar designed the special-profile thread, which is called the T-thread.

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Specialty metals maker Allegheny Technologies Inc. ( ATI ) has entered into an agreement to sell its tungsten materials business to Latrobe, PA-based wear-resistant products company Kennametal Inc. ( KMT ) for $605 million.

Both companies' Board of Directors has approved the transaction. The deal is subject to necessary regulatory approvals and is expected to complete by the fourth quarter of 2013. Until the completion of the transaction, Allegheny will report the financial results of tungsten materials business under its discontinued operations.

Allegheny decided to divest its tungsten materials business so that it can focus more on its core businesses - High Performance Metals and Flat-Rolled Products.. The acquisition is also expected to increase Allegheny's financial flexibility and simplify its capital allocation and deployment.

Allegheny's tungsten materials business operates through roughly 1,175 employees across 14 operating facilities globally and consists of two market-leading divisions - ATI Firth Sterling and ATI Stellram. It produces tungsten powder, tungsten heavy alloys, tungsten carbide materials and carbide cutting tools. The business unit generated $338.6 million of total net revenues and $37.2 million of operating profit for the year ended Dec 31, 2012.

Kennametal will pay for the acquisition partly by cash and partly by available borrowings under its existing revolving credit facility.


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The taper and end clamping faces of the head and the holder are both solid carbide while the threaded part is steel. Other tools with a carbide head and carbide clamping section are usually constructed with a part carbide section brazed to a steel shank, creating an inherent weakness at the joint versus a solid carbide shank, the company said. The exchangeable nature of the series offers chances to reduce inventory and changeovers.

The mills target titanium alloys and heat-resistant alloys such as Inconel, along with stainless steels, carbon and alloy steels and hardened steels. Each head type has irregular helix flutes for vibration control and the four-flute corner radius type can incorporate coolant through-holes. The series incorporates the EP7020 “Smart Miracle” coated carbide grade for improved wear resistance, the company said.

Heads are supplied in five different geometries:

Four-flute corner radius with through coolant – Ø10 - Ø25, with irregular helix for vibration control
Four-flute corner radius – Ø10 - Ø25, with irregular helix for vibration control
Six, 10 and 12 flute – Ø10 - Ø25 for finishing, with irregular helix for vibration control
Four-flute and six-flute ball nose – Ø10 - Ø25, both with irregular helix for vibration control

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Exploration and development firm Premier African Minerals plans to start low-cost production of tungsten mine at its flagship RHA project located along the Kamativi tin belt in Matabeleland North by the end of 2014.This follows a successful technical assessment of the viability of the site, envisaged to produce 192 000 tonnes of tungsten per annum over the six-year life of the mine.

Premier African Minerals has mineral projects located in Western and Southern Africa.Tungsten and its alloys are used to make filaments for electric lamps and television tubes, as electrical contacts, heating elements among other industrial applications.

Tungsten is a metallic chemical element classified among the transition metals of the periodic table of elements and is well known for its strength and durability.

Premier African Minerals said underground tungsten mine development would start once open-cast production had started.

"In line with this we are in discussions with potential funders for the project and possible off-take partners as one route to fast track RHA towards production in the near term with a target production of late 2014," it said.

"The company aims to commence open-pit production development in late 2014, with underground mining development to commence thereafter to fulfils the project's projected six-year life of mine."

Meanwhile, Premier chief executive Mr George Roach said the resource endowment at the project was enough to enable them to recoup their investment. Mr Roach said the latest assessment had further highlighted the attractiveness of the project.

"With a revised net present value of US$120 million (up from US$118 million previously estimated) and a significantly increased internal rate of return before tax of 378 percent now projected, coupled with the low-capex nature of the project with estimated costs of US$13,5 million, excellent infrastructure, low-strip ratio and a relatively simple processing route expected, we approach the next stages of development with confidence," he said.



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