Anatomy of an Endmill
There is a lot of detail involved in endmill anatomy, as seen in the diagram below. Not all are needed in order to properly select a tool, so won’t worry about each minor detail in the diagram.
Flutes - These are the cutters on the endmill. Typically, 2 and 3 flute endmills are used for aluminum and other non-ferrous metals, while 4 flute endmills are used for steels and other harder materials.
Length of Cut - The length the endmill is able to cut. This is not equivalent to flute length.
Neck - This is the portion of the endmill that can rub on the material as the flutes cut during a deep cutting operation. It includes both the top portions of the flutes not suitable for cutting. A necked endmill has a portion of the length above the flutes at a smaller diameter to give it a deeper reach. Necked endmills aren’t the typical style, but they are an option if required.
Shank - Also known as the shoulder. This is the part of the endmill that is grabbed by the toolholder. It cannot cut and should never rub against material.
Coating & Material
TBD
Standard Mill Tools
Square / Flat Endmill
Flat endmills have an extremely sharp corner, with a radius of around 0.002”. These corners wear easily, so they should not be used when roughing out a lot of material. They should be used when a better surface finish on the bottom is desired, or a sharp corner is needed.
Although they aren’t ideal for roughing due to the tool wear, these are the endmills that the capstone shop stocks. When working in there it is fine to use these for roughing.
Bullnose / Radiused Endmill
Bullnose endmills are the workhorse of endmills. They can take away material without much tool wear, while also leaving a flat and unscalloped bottom. They have a radius between that of a flat and ball endmill.
Typical radiuses that are used for roughing are 0.015-0.030”, however there are many options depending on the desired outcome.
Ball Endmill
Ball endmills are used where a smooth contour is desired with the cutting direction involving both up and down in the z-axis. It can also be used to give a large radius to an internal corner. The end radius is equal to the radius of the endmill itself.
Facemill
Facemills are a desirable option for facing. They result in very smooth finishes and take away a lot of material in stepover while not taking away very much in stepdown. They usually have a few cutting inserts that can be flipped or replaced when one gets damaged or worn down.
Specialty Mill Tools
Keyseat Cutters
Keyseat tools are used to undercut some material, where you want to create some sort of internal groove that a typical endmill could not. These are usually purchased on an application specific basis, as the cutter diameter ratio to the neck and the cutter length will likely need to be pretty specific. These are usually used to cut grooves for retaining rings.
Toolholding
ER-## Collets
These types of collets are the standard for toolholding in the MIE Capstone Shop. ER collets have slits on both their front and backside, which allows for a wider grip range than their 5C counterparts [see Collet Blocks in Mill Workholding].
