End mills are rotary cutting tools used in milling machines and machining centres to remove material by advancing a cutting edge into a stationary workpiece. They are an essential tool for machining aluminium because of aluminium's unique properties.
Aluminium is lightweight, corrosion-resistant, and easy to machine. However, it is also soft and ductile. This can cause issues like gumming, smearing, welding, and rapid tool wear when machining aluminium. Using the right end mill is crucial to overcoming these challenges.
End mills come in a variety of types, each with distinct geometries, flute forms, coatings, and other features that make them suitable for specific applications. Selecting the best end mill for machining aluminium depends on several factors - the desired finish, whether removing large amounts of material or fine finishing, tool speeds and feeds, and more.
This guide will provide an overview of the most common types of end mills used for aluminium and discuss the key considerations when choosing an end mill for your application. With the right end mill selection, you can machine aluminium efficiently and achieve superb finishes.
Spiral Flute End Mills
Spiral flute end mills are the most common type of end mill used for machining aluminium. They have either 2 or 4 flutes that spiral along the length of the end mill. The flutes act as helical conveyors that effectively clear chips and swarf from the cut. This prevents chips from being re-cut and overheating the tool or workpiece.
Spiral flutes offer a good balance of material removal rate, finish quality, and tool life when machining aluminium. The sharp cutting edges shear the material efficiently while the flutes provide space for chip evacuation. 2 flute end mills provide more space between flutes for chip clearance, while 4 flute end mills provide more cutting edges and require lower axial depths of cut. Either can work well for aluminium.
The spiral flutes are oriented in a right-hand cut direction. This means the flutes curl so they cut from the outside diameter towards the centre, pulling chips up and out of the cut. The right-hand cut enables efficient chip clearing, especially when paired with climb milling.
Overall, the simple and effective design of spiral flute end mills makes them versatile and suitable for the majority of aluminium milling applications. Their ability to clear chips and withstand high feed rates is ideal for working with gummy aluminium alloys.
We recommend: Kyocera HPMT K31 series for aluminium.
Ball Nose End Mills
Ball nose end mills are used for 3D contouring work and producing smooth finished surfaces. As the name suggests, they have a rounded nose that allows the end mill to smoothly cut around contours without leaving sharp edges or flat spots.
The key advantage of ball nose end mills is the rounded cutting edge that produces an excellent surface finish. The ball shape allows the end mill to smoothly enter and exit the workpiece without gouging, leaving a clean curving profile. This makes them ideal for complex 3D shapes, sculpted surfaces, and curved contours where a smooth finish is essential.
Unlike standard end mills that have flat bottoms, ball nose end mills have a hemispherical bottom. This allows them to cut an arc rather than a flat bottom trench. The rounded cutting edges mean there are no sharp corners that could leave marks or scratches. This is crucial for workpieces that require a pristine surface texture.
Ball nose end mills come in a range of sizes and lengths depending on the application. Smaller sizes function well for tightly curved areas and details, while larger sizes work better for broad, sweeping contours. The length also determines how deep the end mill can cut. Longer end mills provide enhanced stability and are less prone to chatter and vibration.
When paired with a CNC machine, ball nose end mills excel at 3D finishing work. The CNC can accurately position the end mill as it moves along complex toolpaths to machine intricate forms. This makes them indispensable for mold and die work, prototyping, aerospace, automotive, and countless other applications where exact, smooth finishes are paramount.
Coatings
When it comes to end mills for aluminium, the coating is an important factor to consider. Some of the most common and effective coatings for aluminium include:
Titanium Aluminum Nitride (TiAlN)
TiAlN is a very popular coating for aluminium end mills. It provides high hardness, heat resistance, and lubricity. The coating helps prevent aluminium from sticking to the end mill, reducing build-up, friction, and heat. This allows faster speeds and feeds to be used. TiAlN has a gold colour.
We recommend: HTB (ALUSpeed) from Kyocera Hardcoating Technologies.
Factors to Consider
When choosing the best end mill for aluminium, there are several factors to take into account:
Type of Aluminium Alloy
- The most common aluminium alloys used in manufacturing are 6061, 7075, and 2024. 6061 is one of the least machinable but most versatile of aluminium alloys. It has excellent corrosion resistance and average machinability. 7075 is harder and stronger than 6061, but cracks easily during machining. 2024 is an alloy with good fatigue resistance used extensively in aerospace applications. It also has low machinability.
- Harder aluminium alloys like 2024 and 7075 require sharp cutting tools, slow speeds, heavy feeds, and rigid setups. Softer alloys like 6061 can be machined faster and more aggressively.
Desired Finish
- A fine finish requires a sharp end mill, lower speeds, and shallow depths of cut. Ball nose end mills produce the best finish.
Speeds and Feeds
- Follow the end mill manufacturer’s recommended speeds and feeds. Reduce speeds by 20-30% when machining harder aluminium alloys.
- Use slower speeds for finer finishes. Higher speeds can be used for roughing passes.
- Use heavy chip loads and feed rates for aluminium. This prevents rubbing and work hardening.
Coatings
- Uncoated end mills work well for aluminium. But coatings like TiAlN or Kyocera Hardcoating's ALUSpeed improve heat and wear resistance.
Recommendations
For spiral flute and ball nose end mills, we don't believe you can get better than the Kyocera HPMT K31 Series. The ALU series is specifically designed for non-ferrous materials such as aluminium alloys. It comprises a wide range of tools, including ballnose cutters, roughing endmills, reduced shank tools, long-neck tools and more.
For coatings, we work with Kyocera Hardcoating Technologies who produce a coating specifically for the cutting of non-ferrous materials called HTB or ALUSpeed with an ultra-low coefficient of friction.
If you'd like more information on the above products, we are more than happy to have a chat about your procedures and needs.