Iscar Tapping into the future - or is thread milling a versatile alternative?

Author / Editor: Andrei Petrilin, technical manager of indexable milling, and Eran Pinko, thread milling team leader / Barbara Schulz

Israel – Continuing technical progress in machine tool technology has resulted in thread milling becoming an increasingly popular process. Today’s CNC machine tools provide effective cutting by helical interpolation, which makes thread milling more attractive for manufacturers.

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Iscar’s design approach to thread milling tools is based on indexable or solid carbide cutters.
Iscar’s design approach to thread milling tools is based on indexable or solid carbide cutters.
(Source: Iscar)

Although tapping continues to be the most commonly used internal threading generation process, the highly efficient thread milling technique has ended the absolute domination of tapping as the main method of cutting threads in relatively small diameter holes.


Tapping poses the problem of chip evacuation

Even though tapping is considered a highly productive process, together with its obvious pros this traditional method also has evident cons. The main problem encountered when performing a tapping procedure is chip evacuation. A long chip can clog the flute of a tap, which may cause the tap to break in a hole, and as a result, possibly cause an entire machined part to be scrapped. However, when performing thread milling, effective chip evacuation is achieved without difficulty.

The problem of material hardness is another common impediment to efficient tapping. Although the majority of today’s taps are not suitable for the machining of hard materials, thread mills that are produced from solid carbide considerably expand the range of hard materials that are able to be tapped. Thread milling delivers outstanding versatility. For instance, a single multiple-form thread mill is able to produce screw threads with the same pitch in holes of different diameters. In addition, a single point thread mill of a partial profile is also suitable for machining threads in accordance with various standards, for example, both ISO metric and American National. In comparison, the dedicated nature of a tap means that it can only be applied to a thread of a specific diameter and pitch. Also, a thread mill is an excellent tool for making threads in blind holes.

Thread milling enables the ability to overcome a range of previously met tapping problems, such as tool bending, wear and material “springiness”.

Global industry has widely accepted thread milling as a preferred option

Despite the growth of thread milling, the traditional tapping method has important advantages (ease of operation, minimizing the work of a machinist, etc.), which explain its continuing widespread use. However, the global industry has so widely accepted thread milling as a preferred option that it is simply impossible to imagine manufacturing without mills that make threads.

In response to the growing trend, the world’s cutting tool producers now offer the customer a wide choice of different thread mills. As a leading manufacturer of cutting tools and an acknowledged expert in this area, ISCAR has developed a wide range of advanced thread milling products, including indexable and solid carbide tools.

An indexable tool that carries replaceable carbide inserts may have a design configuration such as a mill with shank or a shell mill with a central bore for mounting on an arbor. The main advantage of indexable tools is their great versatility. By changing the inserts, the tool can turn into a cutter for milling external or internal threads which meet the requirements of different standards. Moreover, this process may enable users to find a more effective cutting geometry depending on the material of a machined workpiece. Each of these tools has internal channels to enable the delivery of an effective coolant supply into the cutting zone. One solution is to use helical threading inserts in MTSRH indexable tools.

The helical cutting edge of the inserts, as in solid carbide endmills, ensures an easy and light cutting action, significantly improving the performance of the tool. In addition, inserts with smooth helical cutting edges can be mounted onto the tools. Therefore, the MTSRH tools may also be applied to the finish milling of square shoulder, and as a result, they can successfully compete with 90°milling cutters.