What are flat surfaces and how are they machined?

You may have heard the term “flat surface” in the metalworking industry. But what are flat surfaces and what machining processes can be carried out on them? Which machine tools work on this type of surface?

Characteristics of flat surfaces

If you have wondered what flat surfaces are, their definition is closely linked to geometry. In that discipline, flat surfaces make up the faces of the geometric solids that rest on a common point called the base. Flat surfaces coexist with the curved surfaces of round bodies.

In the machining industry you can find countless parts with flat surfaces. It is important not to confuse a part being flat with it being smooth or rough. For example, tubes have a smooth surface, but they are curved surfaces. What are these flat surfaces? We can mention, specifically, the sheets or plates of different materials, which are characterised by being flat sheets produced by the bending or forming of different materials.

However, there are many other flat surfaces that can be machined through different procedures.

Machining flat surfaces

Now that you know what flat surfaces are, it is worth looking at the machine tools and the different machining processes that can be applied to this type of part.

Grinding

The grinding of flat surfaces is one of the most frequent machining jobs in the metalworking industry. It is an abrasive procedure in which the metal part is polished by the action of a tool called a grinding wheel. The grinding wheel rotates at high speed to wear down or grind the surface of the part being worked.

As a result of this type of machining, the parts will have a smooth, polished surface. Grinding uses a machine called a grinding machine. There are different types of grinding machine but, to polish flat surfaces where very precise work is required, the orbital grinding machine is used.

In the case of grinding flat surfaces, the aim is to produce surfaces that are parallel to the plane, to a depth and quality defined beforehand. The results of this procedure will vary according to the characteristics of the grinding wheel and its speed over the part.

Machining flat surfaces by milling

Machining can be done with or without swarf removal, or by abrasion. Grinding belongs to this third group, while milling falls within machining by swarf removal. Swarf is the small strips removed from the surface of a part being machined.

Milling is carried out on a specific machine tool, fitted with a cutting tool that has several cutting edges and teeth, called a milling cutter. The cutter can move in almost any direction along the three axes on which the machine table travels, and on which the workpiece is clamped.

Milling can shape flat surfaces with different profiles, but it can also drill holes in parts. Depending on the movement the cutter makes, we speak of one type of machining or another; for example, when the axis is parallel to the surface of the part, it is called cylindrical milling; if it moves in the same direction, it is known as normal or climb milling. However, when the axis of the cutting tool is perpendicular to the surface of the part, we speak of face milling.

But how do you machine flat surfaces on a milling machine? On this machine tool, which is known for its versatility, flat surfaces can undergo many different transformations. For example, on a milling machine you can slot or cut grooves in flat surfaces of different sizes; you can also drill holes in the same surfaces or wear down a surface, by swarf removal, until the part takes the shape you want.

Bending flat surfaces

As we have already mentioned, one of the most common flat surfaces in metalworking is the sheet or plate. Sheets, which can be made of stainless steel, aluminium and carbon steel, are obtained through a machining process called bending or forming. It is important to note that this type of machining does not remove swarf, because it only involves the deformation or transformation of a material into a flat plate.

The purpose of bending is to shape a flat surface through a deformation process carried out on a precision machine called a press brake. The sheet bending process is very quick, but complex, because turning a material into a flat surface requires the application of a specific force or pressure.

On this machine tool, the part to be machined is placed between the punch and the die or base and a mechanism is activated that applies pressure at the midpoint of the part.