Video: Thread Mill Without a Pilot Hole

This tool can drill a hole and mill threads simultaneously.


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Successful job shops tend to be the most flexible, adaptive and responsive of machining businesses. There’s no guarantee any one job will repeat, so these companies must set themselves up to process a wide variety of work in an efficient and timely manner.

This means thoughtful decisions must be made about what type of equipment they will use to quickly turn a variety of jobs, often in small batch sizes, for their customers. For example, some shops try to standardize on the types of cutters they use and keep loaded in a machine’s automatic toolchanger (ATC) magazine. That way, setups can be faster, because fewer tools have to be added and measured/touched-off for each new job.

Therein lies the value of a thread-milling tool. An alternative to size-specific taps, thread mills use interpolating motion to mill internal threads in a variety of hole diameters. This is particularly helpful to job shops in that they don’t have to keep a number of taps of different sizes on hand and don’t require special tapping heads. In fact, Mitsubishi Hitachi Tool Engineering, a division of Mitsubishi Materials, takes this one step further with its Epoch D line of solid carbide thread mills that don’t require a pre-drilled pilot hole. These tools simultaneously drill the hole as they mill the threads, using a proprietary cutting edge shape that is said to prevent edge tip breakage even when machining hardened steel. (The video above shows this.)

Combining operations in this way can not only speed overall cycle times, but it also frees additional ATC carousel stations that shops can keep loaded with other tools. In addition, the tool load for a thread-milling process is lower than tapping, and thread mills won’t become stuck in a hole if breakage occurs, as can happen with taps, especially when workpieces are made of hard materials. Plus, right- and left-hand thread milling can be performed with the same tool just by changing the NC program.

The Epoch D thread mill also features the company’s ATH coating applied using physical vapor deposition (PVD) nanotechnology that is said to improve the tool’s hardness and oxidation resistance compared to the previous TH coating. This results in longer tool life in materials harder than 45 HRC. These thread mills are available in metric (M2 through M20 thread size) and UNC (No. 1-64 UNC to 5/8-11 UNC thread size) versions.