Inside the impact of inserts

Over time, innovative products and ideas have been introduced that significantly altered the landscape of machining. Screw cutting lathes, EDMs, CNCs, CAD/CAM software and lasers are all milestone technologies on the manufacturing timeline.

In the 1920s, scientists and engineers brought cemented carbides to the market. That substantially affected the path of metalcutting, not only boosting productivity but changing machine tool design. Shortly after cemented carbides arrived, so did the tools we commonly refer to as inserts.

CNC machine tools, EDMs and lasers are far more exciting than carbide inserts, and it is easy to see how these technologies have helped manufacturing. However, the common carbide insert may well have had a much larger impact than all the other developments combined.

Before inserts, cutting tools had to be sharpened when dulled. This required them to be removed from a machine tool and transported to another location where someone would manually grind them to restore cutting edges. Today, we recognize the disadvantages of having to take off tools for sharpening. Increased tool inventories, lost production and longer setup times are just some of the downsides. The introduction of carbide inserts changed all this. A person now simply indexes, or turns, an insert to a fresh cutting edge or replaces a fully worn insert, and a machine tool is ready to run with no setup and minimal adjustment.

This is one of the largest drills at Mitsubishi Hitachi Power Systems Americas. The drill uses three inserts, and about 10 minutes is needed to change all three. A special piece of grinding equipment and several hours would be required to sharpen an HSS drill this large. Images courtesy of Christopher Tate

Variety is another advantage of carbide inserts. Before, tools were typically solid HSS or had steel shanks with carbide pads brazed on the end. Variation in workpiece materials requires variation in cutting tool materials. So HSS and brazed tools are manufactured with different recipes, thereby producing multiple grades with various levels of hardness and toughness. While many grades of HSS and brazed tools are available, inserts are manufactured in countless grades and new grades are continually added, giving far more options to users than HSS or brazed technologies.

The Incredible Insert
Inserts also provide advanced chip control geometries that can be paired with a specific substrate and coating to further enhance tool performance. Previously, HSS and brazed tools required users to add chip grooves to the rake face if chip control was necessary. This added to the complexity of reconditioning and often was done by hand, which provided varying results. With inserts, users can open a tool manufacturer’s catalog and select from a vast array of geometries. More importantly, when a user develops a machining process, a manufacturer can offer several geometries for testing, making the development process much quicker and easier.