What Is Thread Milling?
Thread milling is a new threading tool that replaces the “tap” used for normal threading in cutting tools.
Unlike taps, which require drilling a pre-drilled hole of the appropriate size before machining, thread milling does not require a pre-drilled hole and allows simultaneous drilling and threading with a single tool, significantly reducing tool changeover time.
Also, compared to taps, there is less risk of chips clogging up, reducing the risk of breakage due to clogging, and even in the event of breakage, removal after breakage is easy because the tool does not clog the hole.
Uses of Thread Milling
Thread milling is used for threading workpieces in the same way as taps, but because thread milling is carbide tools, they can also thread materials that are harder than taps (tool steel and hardened steel).
In addition, since the load on the machine is less than that of a tap, it can be used even on small machining centers with low rigidity.
Furthermore, even in special threading operations such as left-hand threads and fine threads, all can be machined with a single tool by simply changing the NC program, eliminating the need for multiple dedicated taps.
Principle of Thread Milling
While a tap threads a pre-drilled hole perpendicularly, thread milling threads a hole by moving the XYZ axis simultaneously, drawing a spiral while digging through the metal (helical machining).
Therefore, different size threads can be cut if the pitch is the same, so various types of threads can be cut by changing the NC program, and the accuracy of the female thread can be easily adjusted by changing the diameter compensation.
Also, some thread milling has a chamfering edge on the tip, so the processes of pre-drilling, tapping, and chamfering can all be integrated into a single threading machine, a feature unique to thread milling.
However, there are some disadvantages to this seemingly versatile tool.
First, while taps are machined using only Z movement, thread milling is machined using simultaneous XYZ control of all three axes, making NC programs more complex. The machining time is also longer due to the complexity, so it takes too much time when drilling many identical holes.