Thread milling has become increasingly popular within the global metalworking industry. Today’s CNC machine tools provide effective cutting by helical interpolation, and this advantageous feature ensures a growing trend of thread generation by the milling process.
Although tapping remains the most common internal threading generation process, the highly efficient thread milling technique has ended tapping’s dominance of as the main method of cutting threads in relatively small diameter holes.
Even though tapping is considered highly productive with some obvious pros, this traditional method also has evident cons. The main problem encountered when performing tapping is chip evacuation. A long chip can clog the flute of a tap, which may cause the tap to break in a hole, and possibly cause an entire machined part to be scrapped. However, when performing thread milling, effective chip evacuation is achieved without difficulty.
Material hardness is another common impediment to efficient tapping. Although the majority of today’s taps are not suitable for machining hard materials, thread mills 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 tapping problems, such as tool bending, wear and material “springiness”.
Despite the growth of thread milling, the traditional tapping method has important advantages (ease of operation, minimising the work of a machinist, etc.), which explain its continuing widespread use. However, 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, cutting tool producers now offer customers a wide choice of different thread mills. 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 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. An ingenious 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, 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.
Iscar’s family of solid carbide thread endmills feature a comprehensive range of cutters that have a range of profiles for the generated various threads, diameters, overall lengths and neck lengths. In addition, two separate coolant supply arrangements are available: one central hole, or coolant outlets located in flutes. Largely, Iscar’s design approach to thread milling tools is based on indexable or solid carbide cutters. However, Iscar also supplies a unique product – a replaceable, solid carbide Multi-Master head for thread milling.
Launched more than 15 years ago, the Multi-Master range is a family of modular tools that comprises shanks and interchangeable carbide heads. Although originally intended mainly for die & mould applications, Multi-Master’s versatility ensured it soon became popular in many other industrial sectors. This popularity inspired the introduction of thread milling heads to the range, further extending Multi-Master’s flexibility.
Today, Multi-Master provides customers with many more options, including single point milling heads for a 60°and 55° partial thread profile. Also, Multi-Master successfully adopted the cutting geometry of solid carbide multiple-form thread endmills for interchangeable cutting heads. These heads are designed for milling internal and external threads in accordance with ISO, UN, UNF, UNEF and BSP specifications.
For the customer, the availability of a wide variety of Multi-Master shanks significantly simplifies the assembly of optimal tool configurations for specific threading operations. The use of Multi-Master also allows users to slash tool stock and remove the need for special (tailor-made) thread mills. The introduction of the new thread milling heads allows more effective use of the shanks that are already in operation in other processes, and increase utilisation rates. When compared to solid carbide thread mills, Multi-Master provides more reasonable and sustainable utilisation of cemented carbide. Therefore, by further expanding its applications into thread milling, Multi-Master has become the ideal multi-functional tool family.