‘Tapping’ into the Future with Thread Milling

‘Tapping’ into the Future with Thread Milling

Continuing technical progress in machine tool technology has resulted in thread milling becoming an increasingly popular process within the global metalworking manufacturing industry.
 
Today’s CNC machine tools provide effective cutting by helical interpolation, and it is this advantageous feature that ensures the growing trend of thread generation by the milling process.
 
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.
 
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.
 

…a single multiple-form thread mill is able to produce screw threads with the same pitch in holes of different diameters.

 
fig.2Thread 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 (e.g. 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’.
 
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, 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.fig.1
 
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. An ingenious solution is to use helical threading inserts in MTSRH indexable tools.
 
The helical cutting edge of the inserts, as in solid carbide end mills, 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.
 
ISCAR’s family of solid carbide thread end mills feature a comprehensive range of cutters that have a range of –
 

  • -Profiles for the generated various threads
  • -Diameters
  • -Overall length and neck lengths

 

fig.3In 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 MULTIMASTER head for thread milling.
 
Launched more than 15 years ago, the now renowned MULTIMASTER range is a family of modular tools that comprises of shanks and interchangeable carbide heads. Although originally intended mainly for Die and Mold applications, the impressive versatility of MULTIMASTER ensured that it soon became popular in many other industrial sectors. This popularity inspired the introduction of thread milling heads to the range, further extending MULTIMASTER’s celebrated flexibility.
 
Today, MULTIMASTER provides customers with many more options; including single point milling heads for a 60° and 55° partial thread profile.
 
MULTIMASTER has also successfully adopted the cutting geometry of solid carbide multiple-form thread end mills for interchangeable cutting heads.Figure 4
 
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 MULTIMASTER shanks significantly simplifies the assembly of optimal tool configurations for specific threading operations. The use of MULTIMASTER 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, MULTIMASTER provides more reasonable and sustainable utilisation of cemented carbide.
 
Therefore, by further expanding its applications into thread milling, MULTIMASTER has become the ideal multifunctional tool family.