Universal metal-cutting machine tools: what are they?

There are two procedures for machining workpieces: manually, with specific instruments; or using universal metal-cutting machine tools. The latter are the most widely used in industry and, in turn, are classified into machine tools, cutting tools and clamping tools.

What is metal cutting?

Metal cutting is a machining procedure carried out in order to obtain specific dimensions for the workpiece being worked. But why is it also known as swarf removal? Because, during the process, small parts of the workpiece, called swarf, are separated off, using, above all in the manufacturing process, a special machine tool.

The machines used can in turn use defined and undefined cutting edges to carry out the cutting process, that is: the waste or swarf removed has a specific geometric shape or does not. In the first case are milling machines, and in the second, grinding machines.

Characteristics of machine tools

In a machine tool the workpieces to be worked are placed and held; then, through the action of specific tools and with specific movements, the removal of the surplus parts is achieved, which are discarded in the form of swarf. All the machines involved in this procedure have similar elements:

• Bed, where the workpieces to be machined are placed.
• Guideways, along which the moving tools of the machine travel.
• Motors that make the machine run.
• Transmissions, which carry the driving motion to the moving parts of the machine.
• The machine also consists of many levers, handwheels and elements that allow it to be operated. Some work with numerical control (CNC).

Universal metal-cutting machine tools

Lathe

Turning is a machining process by material removal that uses a machine tool called a lathe. The workpiece placed in this machine will have a circular movement, while the cutting tool will move in a linear fashion. The workpiece being worked is held in a chuck, while the cutting tool is fixed to a top slide so that it can move and carry out the swarf removal.

The lathe can carry out high-precision procedures and can operate manually, semi-automatically or through a CNC (numerical control), so there are different types of lathe: centre or horizontal, vertical, facing or multi-spindle.

Milling machine

The milling machine is a very common machine tool in the manufacturing and machining of small workpieces. The process carried out by this machine is called milling and is distinguished by the use of a cutter that can have one cutting edge or several and by a head that moves in three directions (X-Y-Z).

The movement carried out is perpendicular to the axis of rotation of the cutter itself, but it can also move by combining the rotation of the cutter and that of the base plate to which the workpiece being machined is held. The cut that is made depends on the movement used.

These machines provide greater precision when removing swarf; this is due to the different movements that can be made. Generally, all three are combined for an efficient cut. There are also different types of milling machine, classified according to their moving parts, their number of axes or the orientation of the main head (to which the cutter is attached).

Drilling machine

The process carried out by a drilling machine is called drilling and consists of producing holes in the workpiece. To carry out this procedure, a drill with cutting edges that move up and down, rotating, is used, penetrating the material to be cut. The drilling machine has a head to which a drill bit is fitted which, as it rotates, removes the swarf.

Different types of tool can be used for drilling workpieces. If you want to do the process manually, the hand drill is used, which is the best known. But other types of machine are also used, such as the pillar drill, the bench drill and the radial arm drill.

Saw

The saw blade is used for machining workpieces through a process known as sawing. This procedure can be carried out manually or by a machine and consists of sliding a saw blade back and forth to make the cut. The main tool is the saw blade, which has teeth able to produce a fine cut in the workpiece being machined. The main feature of the saw blade is that the teeth are set slightly apart, which means that the cut removes swarf or separates the workpiece into two parts.