End Mills - Getting started

End Mills

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Tip Shapes

Eachend mill tip shape is designed for a particular purpose. Some common cutter shapes are ball nose, square, corner radius, and Chamfer.

• Ball nose Mills produce a rounded pass and are ideal for 3D contour work Feeds and Speeds
• Radius end mill is most recommended because they ensure constant smooth cutting and chip removal. Radius edges increase corner edge strength and produce a desired radius and meet functional print requirements.
• A Chamfer end mill will create a cutting action that assists in breaking chips in most materials. Chamfering allows for heavier feed rates and more efficient production. Their angled profile allows chamfer, bevel, and other angled cuts in materials such as aluminum, brass, bronze, iron, and steel.
• Square end mill Commonly referred to as Flat End Mills, they are used for general milling applications including slotting, profiling, plunge cutting, and milling square shoulders. Square End Mills produce a sharp edge at the bottom of the slots and pockets of the workpiece. Flutes on each of the end mills' cutting heads carry chips away from the workpiece to prevent damage to the end mill or workpiece. Square end mills are used on CNC or manual milling machines.

Speed

The speed at which we move a cutter across the material is called the “feed rate”. The most important aspect of milling with carbide end mills is to run the tool at the proper rpm and feed rate. The rate of rotation is called the “speed” and is controlled by how fast the router or spindle turns the cutting tool. Both feed rate and spindle speed will vary based on the material being cut. Certain mills have very specific running parameters relative to their material families. Spindle speed that is too fast paired with a slow feed rate can result in burning or melting.
Spindle speed that is too slow paired with a faster feed rate can result in dulling of the cutting edge, deflection of the end mill, and the possibility of breaking the end mill. A general rule of thumb is that you want to move the tool through the material as fast as possible, without sacrificing surface finish. The longer the tool rotates in any one place, the more heat that builds up. Heat is your enemy and can burn your material or radically decrease the life or your cutting tool.
A good strategy when selecting a cutter is to attempt to balance feed rate and spindle speed by performing two passes on the workpiece. The first pass, called the roughing pass, can be done by using an end mill that will eject a large number of chips at a high feed rate. The second pass, called the finishing pass, they won’t require as aggressive of a cut and can provide a smoother finish at a high speed.
Flute types

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	Two Flutes	Three Flutes	Four Flutes	Six Flutes	Eight Flutes
Advantages	Excellent Chip carrying capacity. Low cutting resistance.	Excellent Chip carrying capacity. suitable for sinking.	Good rigidity	High rigidity. Superior cutting edge	High rigidity. Superior cutting edge on the hardest materials
Disadvantages	Low Rigidity	Diameter is not easily measured	Chip disposability is poor	Chip disposability is poor	Chip disposability is very poor
Uses	Slotting, side milling, sinking, etc. Wide range of uses	Slotting, side milling, heavy cutting, finishing	Shallow slotting, side milling, finishing	High hardness material, shallow slotting, side milling	Used on Hard materials such as steel, stainless steel, iron, and more...

End mills with less flutes on the cutting edge will provide better chip clearance, while end mills with more flutes will be able to a finer finish and operate with less vibration while being used on harder cutting materials.
Two and three flute end mills have better stock removal than multiple flute end mills but a significantly decreased finish. End mills with five or more flutes are ideal for finishing cuts and cuts in harder materials, but must operate at lower material removal rates due to their poor chip evacuation properties.


Milling Problems troubleshooting

Problem	Causes
Vibration	Weak Fixture Tool Overhang is too long Irregular Table feed Axially weak workplace Irregular table feed Vibration in corners Bad stability Cutting Data
Chip Jamming	insert corner damage Edge chipping and breakage re-cutting of chips
Re-Cutting of Chips	Cutting edge fractures Chip jamming Harmful for tool like and security
Unsatisfactory surface finish	Workplace frittering Vibration Back-Cutting Excessive feed per revolution Built-up edge
Machine Power	Cutter Speed Average chip thickness Cutter geometry Amount of metal to be removed
Burr Formation	Notch main wear mechanism Material Specific HRSA/stainless steel