One explanation for two popular, yet different CNC Machining Centres
There are two machining centre forms, the horizontal and vertical. This refers to the main spindles orientation. Both the horizontal and vertical machining centres come in small, bench-mounted devices to a room-sized machine.
Horizontal machining centres have x – y table with cutter mounted on a horizontal arbor across the table. Most horizontal machining centres highlight a =15/-15 degree rotary table allowing one to mill at shallow angles. Horizontal machining centres are often used to mill grooves and slots. It may also be used to shape flat surfaces.
Vertical machining centres have its spindle axis vertically oriented. Its milling cutters are held in the spindle and it rotates on its axis. Generally, the spindle could be extended to allow plunge cuts and drilling, although the table could also be lowered or raised. The vertical machining centres have two subcategories. These categories are the bedmill and the turret mill.
Although they may be similar since both are machining centres, vertical and horizontal machining centres serve different purposes. Horizontal machining centres were first to appear to put milling tables under lathe-like headstocks. However, through the desire to change the angle of the horizontal machining centres, accessories such as add-on heads were created to convert the horizontal to vertical machining centres.
Horizontal machining centres work best with heavy work piece that needs machining on multiple sides. Die sinking on the other hand is best with vertical machining centres.
Sections of this article have been taken from www.buyusedmachinery.org