Why End Mills
An end mill is a type of milling cutter, a cutting tool used in industrial milling applications. It is distinguished from the drill bit in its application, geometry, and manufacture. While a drill bit can only cut in the axial direction, most milling bits can cut in the radial direction. Not all mills can cut axially; those designed to cut axially are known as end mills.
End Mills are used for making shapes and holes in a workpiece during milling, profiling, contouring, slotting, counterboring, drilling and reaming applications. They are designed with cutting teeth on the face and edge of the body and can be used to cut a variety of materials in several directions.
End Mill Types:
- Square end mills are used for general milling applications including slotting, profiling and plunge cutting.
- Ball end mills, also known as ball nose end mills, are used for milling contoured surfaces, slotting and pocketing. A ball end mill is constructed of a round cutting edge and used in the machining of dies and molds.
- Roughing end mills, also known as hog mills, are used to quickly remove large amounts of material during heavier operations. The tooth design allows for little to no vibration, but leaves a rougher finish.
- Corner radius end mills have a rounded cutting edge and are used where a specific radius size is required. Corner chamfer end mills have an angled cutting edge and are used where a specific radius size is not required. Both types provide longer tool life than square end mills.
- Roughing and finishing end mills are used in a variety of milling applications. They remove heavy material while providing a smooth finish in a single pass.
- Corner rounding end mills are used for milling rounded edges. They have ground cutting tips that strengthen the end of the tool and reduce edge chipping.
Flutes feature grooves or valleys that are cut into the body of the tool. A higher number of flutes increases the strength of the tool and reduces space or chip flow. End mills with less flutes on the cutting edge will have more chip space, while end mills with more flutes will be able to be used on harder cutting materials.
- Single Flute designs are used for high-speed machining and high-volume material removal.
- Two Flute designs have the most amount of flute space. They allow for more chip carrying capacity and are used primarily in slotting and pocketing nonferrous materials.
- Three Flute designs have the same flute space as two flutes, but also have a larger cross-section for greater strength. They are used for pocketing and slotting ferrous and nonferrous materials.
- Four/Multiple Flute designs allow for faster feed rates, but due to the reduced flute space, chip removal may be a problem. They produce a much finer finish than two and three flute tools. Ideal for peripheral and finish milling.
Similarities between drill and end mill
- Both are multi-point cutters as more than one active cutting edges participate in material removal action. It is worth noting that micro-end mills (tool diameter is about 10-50 μm) may also have only one cutting edge; however, such tools are not commonly used.
- In both the cases, material removal takes place in the form of solid chips.
- In both the cases, the cutting velocity is provided through the rotation motion of the cutting tool (drill or end mill). Such velocity is also proportional to the tool diameter and rotation speed.
- Due to physical contact between tool and workpiece, several problems such as tool wear, residual stress, heat generation, etc. are encountered in both the operations.
End Mill Cut Varieties:
- Centre-cutting end mills are those that can be plunged straight down into the material. They can mill, and they can drill. (They have cutting edges on the end face and the sides) These are usually the 2 flutes or 3 flute endmills, and occasionally you can find some 4 flutes that are centre cutting as well.
- Non-centre cutting end mills refers to those that mill, they do not drill. (they have cutting edges only on the sides).
- Up-cut end mills eject chips towards the top of the workpiece, leaving a cleanly cut bottom surface inside your material.
- Down-cut end mills do the opposite, they leave a smooth top surface on your material.
- Compression end mills combine the best of both worlds and produce a smooth surface on both ends of the workpiece when cutting.