When selecting cutting tools there are many different elements that will affect the type of cut you will achieve. Therefore it is important to understand some of the components of a cutting tool and the part that they play.
Flute: The flute is the spiral groove that encircles the tool. It pushes the chips away from the material therefore creating a cut.
Cutting Edge Diameter: The diameter denotes the size of the hole or cut that will be created by the tool.
Flute Length: The cutting depth is essentially how deep into the material that bit will be able to cut.
Cutting Edge: This is the edge that cuts or scrapes away the material as the bit turns. It can have very sharp edges depending on what is being cut and at what speeds.
Shank: The shank is the part of the tool that fits into the tool holder on the machine
Upcut: This is determined by the direction of the flute on the tool. An upcut tool would pull the chips upwards. It is often used for jobs where the speed of cut is more important than the quality of the edge because there is the possibility of the material fraying as the chips are pulled upwards. The tool of choice for metal cutting applications would be one with an upcut.
Downcut: This means that the direction of the flute causes the chips of material to be pushed downward. This type of tool is often used where the quality of the edge is more important than the speed of the job.
Compression Bit: This allows you to have a smooth edge on both sides of the material. It means that the tool has a combination of both an upcut and a downcut at either end. The upper end of the tool would have a downcut thereby pushing chips downward and the lower end of the tool would have an upper cut which would pull the chips upward. Therefore neither edge of the material ends up having the possibility of fray.