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For as long as there鈥檚 been tungsten carbide (which is roughly nine decades), machinists have been brazing small hunks of it to steel shanks and then grinding a sharp edge on the result. These brazed carbide tool bits and boring bars are easy to make, customizable to the application, and inexpensive. Unfortunately, their effectiveness depends on the machinist鈥檚 brazing and grinding skills. And since the tool must be removed from the mill or lathe for sharpening, they also lead to significant and costly machine downtime.

HSS tool bits present a similar story. They鈥檝e been around even longer than brazed carbide. They鈥檙e much less expensive than carbide and there鈥檚 no need for brazing鈥攋ust sharpen the tip however you want and get cutting. Sadly, you won鈥檛 be cutting very long or very quickly because HSS boasts a cutting speed of just one-fourth that of tungsten carbide, and even less compared to some of the newer, coated grades. HSS might be fine for hobbyists with loads of time on their hands, but carbide is the first choice for professional machine shops.

That statement extends to HSS rotary tool bits such as end mills, drills, and reamers, all of which are used daily throughout the manufacturing industry. That鈥檚 a shame. Yes, these tools are less expensive than their solid carbide alternatives, but as mentioned, they鈥檙e also far less wear-resistant, predictable, and productive. These factors explain why leading cutting tool manufacturers emphasize the importance of carbide tooling to their customers and why many have stopped offering HSS cutting tools altogether.

That leads us to indexable carbide inserts, the workhorses of the machining industry. As with old-fashioned brazed tools, indexables also utilize small bits of carbide. The difference is how they鈥檙e attached. Rather than a permanent braze, indexable tooling relies on a screw or clamp to secure the carbide insert to the tool body. When the edge becomes worn, swapping it out only takes seconds. More importantly, there鈥檚 no loss of position or need to 鈥渢ouch off鈥� the tool. Just remove the old insert, stick in a fresh one, and get to work.

Where machinists and toolmakers once had to grind special shapes into their brazed or solid carbide tools, they now have the option of buying off-the-shelf indexable inserts in a huge variety of geometries and styles. Need to cut a 1/16鈥� wide groove in a shaft? How about an Acme thread, or a 45-degree chamfer around a part periphery? These and other insert shapes are readily available, no grinding necessary.

Indexable cutting tools are especially important on CNC machinery, where the need to keep spindles turning at all times is critical. Here, machinists rely on indexable drills鈥攐ften with coolant running through them鈥攖o make holes quickly, followed by indexable boring bars to finish machine them. Indexable face mills true up large flat surfaces; indexable end mills rough out pockets and cut slots; indexable profiling tools trace complex part shapes. There鈥檚 very little that can鈥檛 be machined with indexable cutting tools.

But how do you know what carbide inserts and cutter bodies to buy? And why are there so many different grades of carbide inserts out there? Good questions; we鈥檒l start with the second one first. Unlike a few decades ago, when machinists had just a few grades to choose from, there are now dozens of inserts grades, coatings, and chip-breakers available.

Many of these are tailor-made for specific materials or material groups. For instance, a shop making aerospace components can greatly increase efficiency by purchasing carbide inserts designed for tough, heat-resistant superalloys (HRSA) such as Inconel and Hastelloy. The same is true for medical shops, which tend to cut corrosion-resistant, biocompatible materials like 316 stainless steel, cobalt chrome alloy, and titanium. Automakers can dial in their processes by using inserts optimized for cast iron and low carbon steel, while oil and gas producers benefit from tooling that excels in duplex steel.

Simply put, if there鈥檚 an alloy out there, the chances are excellent that a material-specific carbide grade is available to cut it. However, some shops machine aluminum one day, iron the next, and titanium the day after that, often in low quantities. Does this mean they need to bloat their tool crib with dozens upon dozens of different carbide insert grades and geometries, many of which will only be used occasionally?

Probably not. Just as there鈥檚 no shortage of indexable carbide tooling optimized for certain materials, there鈥檚 also no shortage of excellent general-purpose cutting tools. These represent a middle ground between performance and the tool crib bloat just mentioned. That said, the decision to go the material-specific route is a delicate balancing act鈥攊f a job鈥檚 going to be in the machine for more than a few days or is sure to come around again in a month or two, it almost always makes sense to buy carbide inserts designed for that material.

Last but not least is the whole topic of insert nomenclature. It鈥檚 a deep subject, one filled with exceptions and cutting tool-specific rules. Regardless, most manufacturers follow the ANSI or ISO tool identification system (and sometimes both). We won鈥檛 get into the details here except to say that it uses an alphanumeric code to specifies an insert鈥檚 shape (round, square, triangular, etc.), clearance angle (neutral to positive), tolerance (some inserts are pressed to size, while others are ground), the size of the locating hole (if any) and clamping method, its size and thickness, corner radii, and various other defining features (see the chart above for an example).

Complex naming systems aside, however, choosing the right insert for your machining application isn鈥檛 as difficult as it might appear. That鈥檚 because cutting tool manufacturers have developed online tool advisors that walk machinists and programmers through the tool selection process. For example, JDB电子.com has a collaborative space that prompts users to answer questions聽about the metal removal process (milling, turning, or holemaking), the machine tool that will be used, workpiece material and removal amount, and expected depths of cut. It then generates a machining strategy along with insert and toolholder suggestions, ordering information, product availability, feed and speed recommendations, and more.

Long story short, carbide insert selection is much easier than it once was, even though the number of cutting tool options has grown exponentially since the days of brazed carbide and HSS tool bits. Download a catalog, log in to JDB电子.com聽or give your local cutting tool representative a call. You鈥檒l be making chips in no time.