Thread milling is a metalworking operation used to cut internal and external threads of different sizes through the circular ramping movement of a rotating tool. The thread pitch is created by the lateral movement in one revolution. Different from tapping, thread milling is mainly applied to larger workpieces, however, solid carbide thread mills can also produce small threaded holes. The same machine can be used for both left and right-hand threads, different thread tolerance, various materials, and hole diameters, producing threads with high accuracy and great surface finish. Although not as widely used as thread turning, thread milling can achieve high productivity in some applications.
You're probably thinking, taps carry out the job faster, why is thread milling so big?
Read the next section and you will find out!
A thread is something we see and use everyday without even realising. Get thirsty? You unscrew your bottle lid to have a drink. That there, is a thread. Simply put, a thread forms a coupling between 2 different mechanisms. In this example, the bottle and the bottle lid form together to create a seal holding the water. Threads are measured using GO and NO-GO gauges. These measuring tools ensure the pitch is correct. The NO-GO gauge ensures the pitch diameter is above the minimum, and the Go gauge ensure it is below the maximum. There are other methods experienced engineers use to save the cost of a gauge, however gauges are the most reliable and efficient method.
Most CNC milling machine operators will have different opinions on their preferred type of cutting tool for a specific application that is based strictly on past experience because it is natural to repeat strategies that have succeeded in the past. However, a better-educated decision can result in even better results. Walter Tools made a fantastic video explaining this.
To summarise, both types are very effective. However it all comes down to the job you’re carrying out. There are so many factors which come into play to picking the perfect tool. Hole diameter, workpiece material, size of the job, how many threads, cost effectiveness, cycle time of changing tools, and so many more. If you need help, please call us today and speak to our technician!
High-quality and suitable thread milling tool is essential to avoid failure and problems during the process, you can select some qualified tooling manufacturers and compare their advantages and disadvantages, and choose the one closest to your request. Before that, you need to master the types of thread mills (Helical flute thread mills, Straight flute thread mills, Single profile thread mills, Indexable insert thread mills, Solid carbide thread mills, etc.) and specifications of those thread milling cutters (Single form, Tri-form, and Multi-form), like diameters.
Separate the thread milling operation into several radial passes can achieve higher quality, improve the thread tolerance, ensure safety and avoid tool breakage in difficult-to-machine materials, as well as make it suit in difficult applications, like long overhangs and unstable conditions.
Apply proper tool or strategy to break and evacuate chips timely, cutting fluid and lubricant can be considered, avoid chip recutting, save time and guarantee the tolerance of thread.
Left or right-hand threads are depending on the selected tool path. Which one is more suitable for you? Choose the more efficient one according to your experience.
Generally, the depth of the thread should be no more than one and a half times the diameter of the hole. Because the longer the milling tool, the more chance it can experience deflection, which can create inaccuracies in the thread.
See below for our most popular Threading Tools!