There are many different things that can be done on a mill. Here is some basic terminology:
Operation / Toolpath - A portion of the CAM using one tool and dedicated to a particular feature
Job - A collection of operations in which the part does not move from the workholding and the origin is kept constant
Conventional vs. Climb Milling
These two terms relate to the direction the endmill moves translationally compared to how it moves rotationally.
The choice between the two is somewhat based on personal preference, but usually on CNC machines climb is preferred for a better surface finish. This can take longer to machine in some situations however.
For example, if facing a part, you can choose conventional, climb, or both. Both will make the operation go faster, since the tool doesn't have to pick up and move all the way to the other side before cutting again. If a better finish is desired though, climb only can be selected at the cost of longer machining time.
Stepover & Stepdown
Stepover - How far on the x and y axis the tool moves over in each successive pass.
Stepdown - How far down the tool moves over on the z axis in each successive pass.
Endmilling
Face
Facing is when the tool takes away material top-down. This can be done with a typical endmill, but there are dedicated tools such as face mills and fly cutters which are designed for facing. These specialized tools will give a better surface finish.
Profile
Profiling is taking material away from the sides, specifically on the peripheral of the part.
Pocketing is taking away material in a profile, but on the inside of a part. There are three main ways the endmill gets to the inside of the part: helical ramping, linear ramping, and predrilling.
Helical Ramping - Endmill cuts downwards by ramping in a tight circle, once it gets to the desired depth it will cut sideways into the rest of the pocket
Linear Ramping - Endmill cuts downwards by ramping in a straight line or curve following the pocket’s profile, once it gets to the desired depth it will cut sideways into the rest of the pocket
Predrilling - Drill the size of (or larger than) the endmill drills to the bottom of the pocket, endmill lowers down into the hole and then cuts sideways into the rest of the pocket
Slot
Slotting is when an endmill takes away material at full thickness. This loads the tool much more than other operations and requires more gentle toolpaths.
Contour
Contouring creates 3D shapes. It is usually done with a radiused endmill (either bullnose or ball end), as this technique can be rough on the sharp edges of a flat endmill.
Holemaking
Drill
Drilling involves sending a drill straight down into the part to create a hole. There are a few different types of drills that are used for different purposes: twist drills, spot drills, and center drills. Starting a hole by spotting with a spot drill or center drill helps to keep the long drill from walking when entering, resulting in a more accurate hole location and less tool wear.
Twist Drill - The typical drill bit that cuts a hole.
Spot Drill - A very stubby drill bit used to start a hole. Usually better than center drills, but more expensive.
Center Drill - A very stubby drill bit used to start a hole. Designed to create a hole good for a live center on a lathe. Usually cheaper than spot drills.
Reamer
Reaming expands a hole made by a drill to a precise diameter (below 0.001”).
Thread
Threadmilling is a way of creating threads in a hole or externally on a boss without having to use a tap or die by hand. The threadmill will spiral in the shape of the threading, taking a little but away in each successive pass. This can be used for large threads that are annoying to tap or for threads that need to be extremely concentric.
