2) Types and construction features of milling machine

Vertical mill
The spindle axis is vertically oriented. Milling cutter are held in the spindle and rotate on its axis. The spindle can generally be extended or the table can be raised and lowered, giving the same effect, allowing plunge cuts and drilling. There are two subcategories of vertical mills; they are bedmill and the turret mill.
· Turret mills, like the ubiquitous Bridgeport, are generally smaller than bedmills, and are considered by some to be more versatile. In a turret mill the spindle remains stationary during cutting operations and the table is moved both perpendicular to and parallel to the spindle axis to accomplish cutting.
· Bedmill, however, the table moves only perpendicular to the spindle's axis, while the spindle itself moves parallel to its own axis. Also of note is a lighter machine, called a mill-drill. It is quite popular with hobbyists, due to its small size and lower price. These are frequently of lower quality than other types of machines, however.
Horizontal mill
Has the same sort of x–y table, but the cutters are mounted on a horizontal arbor across the table. A majority of horizontal mills also feature a +15/-15 degree rotary table that allows milling at shallow angles. While endmills and the other types of tools available to a vertical mill may be used in a horizontal mill, their real advantage lies in arbor-mounted cutters, called side and face mills, which have a cross section rather like a circular saw, but are generally wider and smaller in diameter. Because the cutters have good support from the arbor, quite heavy cuts can be taken, enabling rapid material removal rates. These are used to mill grooves and slots. Plain mills are used to shape flat surfaces. Several cutters may be ganged together on the arbor to mill a complex shape of slots and planes. Special cutters can also cut grooves, bevels, radii, or indeed any section desired. These specialty cutters tend to be expensive. Simplex mills have one spindle, and duplex mills have two. It is also easier to cut gears on a horizontal mill.
Different between the vertical and horizontal milling machine
• Vertical milling machines must use smaller cutting tools than horizontal
mills because they have less rigid, less massive castings, and lower
horsepower motors. Still, they can accomplish the same end results as the
horizontal mill, just more slowly.
• Vertical milling machines are less complex than horizontal machines
because the one-piece tool head eliminates the need for complicated
gearing inside the vertical column.

Other types of milling machine variants and terminology
Column mills are very basic hobbyist bench-mounted milling machines that feature a head riding up and down on a column or box way.
Turret or vertical ram mills are more commonly referred to as Bridgeport-type milling machines. The spindle can be aligned in many different positions for a very versatile, if somewhat less rigid machine.
knee-and-column mill refers to any milling machine whose x-y table rides up and down the column on a vertically adjustable knee. This includes Bridgeports.
Planer-style mills are large mills built in the same configuration as planers except with a milling spindle instead of a planing head. This term is growing dated as planers themselves are largely a thing of the past.
Bed mill refers to any milling machine where the spindle is on a pendant that moves up and down to move the cutter into the work. These are generally more rigid than a knee mill.
Ram type mill refers to a mill that has a swiveling cutting head mounted on a sliding ram. The spindle can be oriented either vertically or horizontally, or anywhere in between.
Jig borers are vertical mills that are built to bore holes, and very light slot or face milling. They are typically bed mills with a long spindle throw. The beds are more accurate, and the handwheels are graduated down to .0001" for precise hole placement.

There are two basic construction types of milling machines: the column and knee machines and the fixed bed machines. As the name indicates the column and knee mills have a knee attached to the column which is elevated by a jack screw. The fixed bed construction (found in most CNC machines) does not have a knee. Only the spindle can change elevations. This more rigid machine than the column and knee configuration.

Head - part of the drive system that transforms electrical power from a motor to mechanical power in the spindle.
Quill -moves vertically in the head and contains the spindle in which cutting tools are installed.
Quill feed hand wheel -moves the quill up and down within the head as does the quill feed lever.
Knee- moves up and down by sliding on ways that are parallel to the column.
Saddle -sits on the knee and allows translation of the worktable.
Column -main function is to hold the turret.
Turret -allows the milling head to be rotated around the column's centre.
Over arm - (ram) slides on the turret and allows the milling head to be repositioned over the table.
Longitudinal traverse hand wheel- moves the worktable to the left and right cross traverse hand wheel- moves the work table in and out.
Vertical movement crank -moves the knee, saddle, and worktable up and down in unison.