![]() Geometry is a huge determinant of end mill performance, and there is a lot to cover. They stay sharp longer because they expose more of the extremely hard and heat resistant tungsten carbide and less of the relatively delicate filler.īy the way, some of the best carbide grades are made from carbide recycling, plus it takes 70% less energy to use recycled carbide. Yet, by doing so, we get much better performance from our cutters. Smaller carbide grains are better for end mills because you get more carbide and less filler…Īs it turns out, the smaller grained cemented carbide formulations are more expensive to prepare, especially if the highest quality standards are maintained. Here is an illustration of this large grain/small grain packing phenomenon: Think of the ball bearings as the tungsten carbide grains and the water as the binder. Which container can hold more water? The container with the larger balls has more space between the balls for the water, and hence holds more water. ![]() Then we proceed to fill each container with water until it is full to the top. Suppose we fill one container with large balls and another same-sized container with much smaller balls. As the grains of tungsten carbide get smaller, there are more of them relative to the binder. Manufacturers use terms like “sub micron” and “micrograin” to describe the better grades. This can come about either by way of how the material is prepared or because of the grain size. Cheap carbide has a lot more binder than expensive high quality carbide. Hence, a lot of the quality of the carbide is a function of how much tungsten carbide grains there are versus how much binder. More about end mill coatings below.Īs one would expect, it is the tungsten carbide and not the binder that does the serious cutting. In addition, there may be a very thin end mill coating to further enhance performance. Nevertheless, The material is not a solid metal at all, but a matrix composed of tungsten carbide (which itself is tungsten and carbon in equal parts) held together with a binder–typically cobalt. BTW, I don’t think they’re trying to pull the wool over anyone’s eyes, marketing just can’t resist more adjectives and you could as easily say they use “solid” to refer to endmills that don’t use inserts. While end mill manufacturers frequently refer to their cutters as “solid carbide”, in truth, they are more accurately called “cemented carbide”. Let’s start with the material carbide end mills are made from. Here’s a video from my CNC Chef series for Cutting Tool Engineering that covers the basics: Our article linked to the left gives you the full details on what’s called for with Titanium. Certain materials, like Titanium, place very specific requirements on tooling if you want to be productive and competitive. This article is from a fairly general point of view. We’ll also tell you the secret to evaluating the economics of whether premium endmills make sense for you or not. ![]() In this article, we’ll take a look at the four main factors that cause end mills to perform differently: the grade or quality of the carbide they’re made from, their geometry, the end mill coatings, and premium quality control. Different endmills really do perform differently, and they sure do come in a wide range of prices. Manufacturer’s recommended speeds and feeds fall into bands depending on the material and type of cut, but they are not all the same. ![]() Many develop fierce loyalties to the brand that has worked for them. End Mill Coatings, Grades & Geometries? Why are some end mills so much more expensive, and are they worth it?Įvery machinist must have wondered about this question at some point. Note: This article is Lesson 8 of our Feeds & Speeds Master Class.
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