A milling cutter that is used mainly to machine on the side of the cutter and so used to profile a part.
End mills do not tend to have a clearance cutting edge on the end and so cannot be used in a plunge type of cutting ie like a drill.
The end mill is used by moving the mill into the material sideways, ie at right angles to the axis of rotation.
The image to the left shows a Dormer 4-flute End Mill.
The end mill can be machining over quite a large length of the mill and the forces can be very high and so it is best to minimise the overhangs and improve the stiffness wherever possible to reduce vibration (we have an article on reducing overhangs and the importance of this) .
The image to the right shows an end mill being used to machine an aluminium crankcase. The outer surface is being profiled with the end mill and a rotary table.
The depth of cut is greater than the depth of cut available for this end mill and so the machining is being done in stages. This did make the final cut difficult and I ended up starting from the top and making a complete final cut around the circumference, before dropping the cutter down at the same cut depth and repeating the circumferential cut.
The roughing end mill has a wavy edge. This means there are many small cutting edges and hence a lot of material is removed.
The multiple teeth at different locations on each edge breaks up the excitation of the force on the cutter and so reduces the chance of chatter.
The downside is a rougher finish and a need to us a standard end mill as a finishing cut.
My experience of cutting gears is with cutting a single tooth at a time and then indexing the gear around one tooth and repeating the process.
In this scenario the gear cutters come in different forms depending on gear module size and the number of teeth on the gear.
In the image of the slot drills you can see that one cutting edge is longer than the other, this allows the cutting edge to be over-centre and so ensure the centred is swept. The centre clearance is different in each of these designs.
Slot drills are available in a number of different sizes, materials and tend to be available as 2 or 3 flute designs.