Our Philosophy on End Mills: Carbide Substrate

The most commonly used term for carbide is “Micro-Grain” but it does NOT really describe the differences that have evolved since the first development of “Micro-Grain” in the past 40-50 years. Fine, Ultra-Fine and Sub Micron grains are some of the current terminology that is used.

Two other commonly used terms are “toughness” and “wear resistance.” We’ve found that neither term can be used as a proper gage. Here’s why:

• Toughness - Fracture toughness is not only a characteristic of the material but also a function of the loading conditions. Carbide rod is measured for "toughness” before geometry has been ground into the tool and a finished, ground tool can vary as much as 300% in “fracture toughness” based upon geometry alone.
• Wear Resistance - Cutting tool wear is a result of complicated physical, chemical, and thermo-mechanical actions. Tool wear is caused by such mechanisms as adhesion, abrasion, diffusion & oxidation that all act together with predominant influence of one or more of them in different situations within the CNC machine, which is quite different from lab testing.

Cemented Carbide is similar to cement in more than name only. Cobalt is the “lime” that holds the Carbide “gravel” together. If a large chunk of carbide is exposed at the cutting edge it will fracture off just like a piece of gravel on a cement walkway edge. 

Destiny Tool Substrates compared to our competitors

Bottom Line: At Destiny Tool, through over a decade of testing, we have selected substrates that work together with our tools for optimal tool life and performance in specific materials. Our substrates range from a transverse rupture strength of 580,000 - 630,000 psi and vary in cobalt content from 10 -12% based upon the specific application that the tool was designed. You can trust that we’ve selected the correct substrate for your application material.