Carbide Inserts

Carbide inserts are replaceable and usually indexable bits of cemented carbide used in machining steels, cast iron, high temperature alloys, and nonferrous materials. Carbide inserts allow faster machining and leave better finishes on metal parts. 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 carbide inserts, as well as many lathe tools and endmills.

To increase the life of 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.

Types of Carbide Inserts

Carbide inserts for wood turning

We offer the latest in wood turning technology including round, square, radius, and diamond shaped carbide inserts and cutters that fit many of the commercial woodturning lathes and tools from companies like, Harrison Specialties, Craft Suppliers, Woodchuck Lathe Tools, Carbide Wood Turning Tools, and Sorby, among others.

All of our inserts and cutters are manufactured to our specifications using high grade carbide with micro-grain size of 0.7-1.0 µm. These micro-grains are combined with a 10% binder that yields a hardness of 1650 HV10. They are then finely ground to a razor cutting edge with toughness and durability for long-lasting, smooth cutting in the most dense hardwoods.

Carbide inserts for metal

Carbide inserts are used to accurately machine metals, including steels, carbon, cast iron, high-temperature alloys and other non-ferrous metals. Carbide inserts are replaceable and indexable and come in a huge variety of styles, sizes and grades.

Carbide inserts can be used at high speeds, which enables faster machining, which results in better finishes. It’s crucial that you select the correct carbide insert for the material that you are cutting or you could risk damaging the insert, the machine and the workpiece.

How we make the Carbide Inserts

Inserts, mainly tungsten carbide and cobalt in various combinations, start out as a powder. Here a container is filled with the right mixture of ingredients for the specific powder ordered.

In the mill, the dry raw material is mixed with a solution of ethanol and water. The result is a gray slurry that is about the consistency of a yogurt drink.

After the slurry has been dried, samples are sent to the laboratory for a quality check. The powder consists of agglomerates, small balls of 20 to 200 microns in diameter. That’s tiny – a strand of hair is 50 to 60 microns thick.

The powder is transported in 100-kg barrels to the pressing machines where the inserts are made. The operator places the pressing tool, a mold for the specific insert about to be pressed, in the machine and enters the order number into the computer. The cavity of the press tool is filled with powder. Each insert is pressed with 12 tons of pressure, and it’s weighted by the machine and controlled visually by the operator. At this stage the insert is extremely fragile, breaking easily.

The pressed inserts need to be heated in order to harden. For this, a sintering oven is used. The oven can take several thousand inserts at a time. The inserts are heated to approximately 1,500 degrees Celsius in a process that takes some 13 hours and fuses the pressed powder into cemented carbide, an extremely hard material. Shrinkage in the sintering process is about 50 percent, so sintered insert is only about half the size of the pressed piece.

After another visit to the laboratory for a quality check, the top and bottom of the insert are ground to the correct thickness. Because the cemented carbide is so hard, industrial diamond – the world’s hardest material – is used to grind it.

When the insert is the right thickness, it’s sent for more grinding to get its geometry and size exactly right. This is the most advanced grinding done in Gimo, using 6-axis grinding plates to achieve very tight tolerances.

Once ground, the inserts are cleaned and sent for coating. At this stage, to avoid any grease or dust, the inserts must be handled with gloves. They are placed in fixtures on a carousel and entered into an oven with a low pressure where they are coated. This is where the insert gets its specific color.

The insert is now finished. Samples from each batch are inspected with a microscope to ensure that the quality is right.

Before being packaged, each insert is inspected again and compared with the blueprints and batch order. A laser marks the insert with the correct grade, and it’s placed in a grey box with a printed label. It’s now ready to be distributed to customers.