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”.