Many of today’s shops involved with micro machining are doing so on extremely hard metals, such as CPM (1-V, 3-V, 9-V) D2, A2 and F7 tool steels, along with hard powdered metals, all of which can be as hard, or harder than, 62-64 Rc. They also micro machine stainless steels like 450, 410, and 17-4 and Titanium and Inconel. For these shops, micro mills designed specifically for such tough materials reduce overall part production cycle times, help increase micro tool life and make micro hard milling cost effective for more parts that would have otherwise been machined using different processes.

Many producers of powdered metal tooling, for instance, have been heavily into micro hard milling over the years and can attest to the benefits of using geometry/material-specific cutters, as opposed to general-purpose ones. These shops admit that a materials approach to cutters is key when selecting the right cutting tool manufacturer—one that offer lines of micro endmills in various ranges designed for and tailored to micro machining specific groups of materials. This involves the development of special combinations of substrates, coatings and geometries unique to each range and aimed at optimizing cutter life and performance.

By incorporating such materials-focused endmills, shops doing hard milling can improve surface finishes to the point of eliminating large amounts of required secondary bench work, which in turn, can reduce production cycle times. Also, these shops gain the flexibility to use either EDM or micro hard milling, since the material-focused cutters have made micro hard milling a more cost-effective alternative than it was in the past.
Shops micro hard milling mold tooling can go through a lot of cutters on a daily basis. And out of those cutters, most sizes can range between 0.004” and 0.019” in diameter. Many of these shops would consider big cutters as those around 0.039” in diameter.

For shops producing powdered metal tooling, micro hard milling operations can involve imparting face detailing on punches and semi-finishing and finishing the surfaces of tooling used in the process. Tooling components are often made from various powdered metals and tool steels, such as CPM (1-V, 3-V,9-V), D2 and F7. Apparent hardnesses can be 55-64 Rc. However, particles within such CPM materials are often more along the lines of 70 Rc in hardness.

Traditionally, a large majority of such tooling components would be sinker EDMed, which would still involve micro milling details in electrodes needed for that process. However, sometimes the EDM process can be time consuming and require secondary benchwork because of required high luster mirror-like finishes.

Instead, micro hard milling these parts with material-focused cutters can significantly reduce the amount of required benchwork to achieve superior surface finishes and eliminate time spent making electrodes. All this, in turn, drastically shortens overall part processing times.