End mills are cutting tools used in CNC machines. The term “end mill” means cutting is done from the active end point. To make different types of shapes, slotting, 3D contouring, various types of end mills are used. These different slotting have different purposes and material requirement so it is necessary for you to understand each type. This will enable you to select the most suitable end mill for your needs.
In this article we will discuss what are the different types of end mills, their application, pros and cons and finally discuss which end mill should you choose.
Side note: Whether you buy ½” end mill or ¼” end mill, the types of end mill does not have to do anything with material’s brittleness or softness. The flutes on an end mill decides if it will cut softer or harder material. The more number for flutes, the harder the material is cut, the lesser the flutes, the softer material is cut.
And even if you look for a 4 flutes end mill supplier considering you may get a better quality production, you should know that the only purpose of different types of end mills is for creating variety of shapes, milling profiles, contouring, slotting or plunging.
TYPES OF END MILLS
Depending upon the usage, the end mills are divided in many categories. Following ae the most broadly known categories for end mills.
- Centre and Non-centre end mills
- Finishing and Roughing end mills
- Indexing and Non-indexing (solid carbide) end mills
- Flat end and Ball nose end mills
- Bull nose end mills
- T-slot end mills
CENTRE AND NON-CENTRE END MILLS
The main difference between center and non-center cutting is that center cutting end mills have cutting edges on sides as well as face of cutter while non-center cutting end mills have cutting edges only on sides. The center cutting end mills are used to create slots, pockets, circular pocketing or surface plunging. Whereas the non-center cutting is used to perform side milling (material removing) on the workpiece.
The center cutting end mills are available mostly in two and three flute end mills. They are expensive and cannot be sharpened. The non-center cutting end mills are comparatively economic and can be sharpened again and also clears chips better.
FINISHING AND ROUGHING END MILLS
The solid carbide finishing end mills are used to achieve smooth finish over a material. They have one end with square shape and a smooth outside diameter that creates smooth finish. They are available in various helix angles and in number for flutes. The greater the helix angle, the smoother the surface and the more number of flutes, the softer material it can plunge.
On the other hand, the roughing end mills have teeth at the periphery of flutes that creates the rough textured surface. During milling operation, these teeth converts the material into small chips. As a result, the material chips-off quickly and avoids vibration.
FLAT END & BALL NOSE END MILLS
The flat-end end mills have flat surface and does not have any gap between teeth. Also known as square end mills, their corners are sharp which generates 90° angle. They come in single-end or double-end and are commonly made from solid carbide. They can be used for profiling, plunging, face milling etc. where they give sharp-edged bottom of a slot or pocket in a workpiece.
The ball-nose end mills or full-radius end mills, have a ball-shape edge with radius equivalent to half diameter of tool. It is used for 3D contouring, making arc grooves, creating curvature like turbine blade, and profile milling such like molds.
INDEXING AND NON-INDEXING END MILLS
The indexing end mills are also known as solid end mills. Unlike end mills with teeth, they have recess to add insert. They have positive cutting edge which removes workpiece by slicing action rather than scrapping that reduces the cutting force and vibrations. You can change the insert here when they get damaged or worn out. They are more load bearing and can take higher feed rates because they produce thicker and manageable sized chips. The biggest con of indexing end mill is they do not come in smaller sizes.
Solid carbide non-indexing end mills have tooth. If it gets damaged, you will have to purchase a new non-indexing end mill. They produce great finishes and are available in small diameters. They apply less pressure on tools and can deliver deeper cuts.
BULL-NOSE END MILL
These are corner radius end mill cutters. They are single-ended tools that makes corner radii and a milled shoulder’s bottom. Compared to square end mills, their milling edges are stronger. It is why they can take higher feed rates, deliver greater productivity and are long-life tools.
T-SLOT END MILLS
The T-slot millers are special category tools. They have 2 insert at upside and 2 inserts in downside. They can be used to make screw slots for beds and tables fixings. Their operation is very advanced because first you need to cut vertical slots to allow shank and neck of T-slot millers enter the cut. They also give good finishing surface and their inserts are also changeable which makes their usage economical.
Various types of end mills can perform different function. Some give rough texture while some give smooth finished surface and some are used to provide smooth 3D profiling. Their selection depends on what type of milling action you require. Having a deep understanding of their various types and functions will help you make the right choice.