While tapping continues to be widely used in operations that require threads, thread milling has been gaining ground during the last few years, especially in shops that routinely deal with exotic materials or are moving towards high-performance machining.
Threading tends to be one of the final operations when machining a part. So any problem during this phase can have catastrophic results, especially if you are machining expensive workpiece materials.
The problem with tapping is that, when your tap is engaged with the workpiece, the cutting edges have problems cooling down. This is true even when using coolant as it generally has a hard time reaching cutting edges already engaged. High-temperature alloys tend to resist heat instead of absorbing it, which means there is a lot of heat transferred into the tap.
We have had our fair share of tools breaking off in the whole, often forcing a long rework operation to save the piece, or even resulting in a total piece scrap.
Solid carbide thread mills are increasing in popularity as helical interpolation tool paths are becoming a standard feature in most new CNC machine tools.
What are the advantages of thread milling over tapping?
Higher hole quality: While most solid carbide thread mills have three teeth, the bulk of the thread-cutting is performed by the first teeth. This is done to reduce the cutting pressure on the tool, reducing deflection and allowing the cutting edges to cool down. However, the most important effect is that the other two teeth are used for cleaning up the threads, increasing the overall quality of the hole.
Minimized Risk of Scrapping: Solid carbide thread mills are smaller than the hole diameter. In case of tool failure, you can safely remove the tool from the workpiece without sacrificing any precious material.
More Software Available: The most effective technique when machining threads is performing climb milling. Spinning the tool counterclockwise, while moving it helically down the hole tends to require writing complicated thread milling routines or adapting them to every new project. However, newer software suites come with packages specially created for thread milling.
Increased Durability: As we mentioned before, tapping requires going hard on your tools, especially when threading high-temperature alloys and metals. Solid carbide thread mills are more heat resistant and accurate, but also allow the cutting edges to cool down and reduce the risk of failure.
One Tool, Many Jobs: Tapping requires tool changes every time there is a variation in hole diameter. This, of course, increases downtime and changes cycles, reducing productivity. Threading mills are a lot more versatile, allowing the machinist to create threads in different hole sizes without having to change the tool. You can even perform internal and external threads with just one tool.
Overall, solid carbide thread mills offer more tool durability, flexibility, and safety when machining high-temperature alloys. However, you need to find the best carbide tools for the job. Online Carbide is an American carbide tool manufacturer that crafts high-quality thread mills for machine shops that require durable and reliable tools. Visit their website or contact them by email at sales@onlinecarbide.com, to get personalized attention from their tool experts.
