Things to Consider When using Carbide End Mills with Various Materials

When you first decide to use solid end mills you have to thoroughly evaluate the process and understand the material that will be machined. Your next step will be to decide what geometry would work best for the process. Because of the many different types of geometries and coatings, using solid carbide end mills can be confusing. Once you have a full understanding of the different geometries and coatings and their capabilities, then using solid carbide end mills becomes simpler.

A rule of thumb is that you use more flutes for light cuts and less or fewer flutes for deeper cuts. This is due to the variability of chip packing, which could destroy the end mill. When a side mill or cut is required and there is concern about metal removal, a larger number fluted end mill with four or more teeth should be used. As always, you will have to calculate the effect of the radial and axial depth to know the precise number of teeth that will be used effectively.

Mathematics is a crucial part of all machine work. There are countless formulas that must be memorized and applied correctly to nearly every aspect of the milling process. In fact not only are machinist skill mathematicians but they must have a full understanding of metallurgy. Machinists must understand the strength of the material that they are cutting as well as its weight, durability, hardness, and performance in extremes of temperature.

Since metals and materials do not all have the same machining qualities different approaches must then be applied to each. Most solid carbide end mills perform well with 1018 steel, which is easily formed, machined, welded, and fabricated with any number of flutes. However, with harder materials, lighter cuts, more flutes, and less cutting speed must be used. More flutes are used at lighter feed rates in order to maintain high production levels.

Aluminum alloys has a tendency to be gummy, which leads to a built-up edge. Therefore, higher speeds and feeds are needed to keep the chips evacuating from the flutes. Aluminum alloys with high silicon as well as other alloys have a high abrasive effect on the cutting tools. High-speed-steel tools can successfully cut silicon aluminum alloys it is recommended that cemented carbides be used due to their superior resistance to abrasion. When a fine finish is needed, the cutting tool should be honed to a sharp edge. Tool wear in unavoidable, however, it should not be allowed to advance too far before changing or sharpening the tool. For best results, a diamond-cutting tool is recommended and even the softest aluminum and aluminum alloys can obtain an excellent surface finish with these tools.

Standard milling cutters can be used successfully in shops where aluminum parts are machined for the best results use coarse-tooth, large helix-angle cutters that have large rake and clearance angles up to 10 to 12-degrees. Standard twist drills can also be used in drilling aluminum and aluminum alloys providing the drills have a high helix-angle. The wide flutes and high helix-angles help to clear the chips from these drills. Carbide tipped twist drills can be used and in most instances afford several advantages in many production applications.

Monel and nickel alloys are machined with high-speed-steel and with cemented carbide cutting tools. Standard cemented-carbide tool holders and tool shanks can be used, which provides acceptable tool geometry. In addition, lightly honing the cutting edge will help if chipping occurs.

Nickel alloys have an increased tendency to work harden. In order to minimize this effect caused by machining, the cutting tools should have adequate relief angles and positive rake angles. In addition, the cutting edges should at all times be kept sharp and replaced as soon as they become dull. This will prevent burnishing of the work surface. The depth of cut and feed should be sufficiently large enough so that the tool can penetrate without rubbing the work.

Coatings are extremely important when working with carbide end mills. This is a very important process that allows the carbide end mill to resist wear. While solid carbide end mills do last longer and perform better in many applications when they are compared to high-speed steel, heat will cause carbide tools to crack. To prevent cracking and the destruction of the carbide tools, technology has created heat- and wear-resistant coatings, which increase the life of the tool and thus increase productivity, by reducing machine down time for the replacement of a tool.