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Non-standard carbide inserts are replaceable and usually indexable bits of cemented carbide used in machining steels, cast iron, high temperature alloys, and nonferrous materials. Non-standard carbide inserts allow faster machining and leave better finishes on metal parts. Non-standard carbide inserts can withstand higher temperatures than high speed steel tools.

Cemented carbides are composed of a metal matrix composite where carbide particles act as the aggregate and a metallic binder serves as the matrix. The process of combining the carbide particles with the binder is referred to as sintering. During this process, the binder eventually will be entering the liquid stage and carbide grains (much higher melting point) remain in the solid stage. The binder is embedding/cementing the carbide grains and thereby creates the metal matrix composite with its distinct material properties. The naturally ductile metal binder serves to offset the characteristic brittle behavior of the carbide ceramic, thus raising its toughness and durability. Such parameters of carbide can be changed significantly within the carbide manufacturer’s sphere of influence, primarily determined by grain size, cobalt content, dotation, and carbon content.

Carbide is more expensive per unit than other typical tool materials, and it is more brittle, making it susceptible to chipping and breaking. To offset these problems, the carbide cutting tip itself is often in the form of a small insert for a larger tipped tool whose shank is made of another material, usually carbon tool steel. This gives the benefit of using carbide at the cutting interface without the high cost and brittleness of making the entire tool out of carbide. Most modern face mills use non-standard carbide inserts, as well as many lathe tools and endmills.

To increase the life of non-standard carbide inserts, they are sometimes coated. Four such coatings are TiN (titanium nitride), TiC (titanium carbide), Ti(C)N (titanium carbide-nitride), and TiAlN (titanium aluminum nitride). Most coatings generally increase a tool’s hardness and/or lubricity. A coating allows the cutting edge of a tool to cleanly pass through the material without having the material gall or stick to it. The coating also helps to decrease the temperature associated with the cutting process and increase the life of the tool. The coating is usually deposited via thermal CVD and, for certain applications, with the mechanical PVD method at lower temperatures.