What is drilling and how is it done?

Drilling is not a new technique; it has its origins in the Stone Age. What is drilling and how is it used in the metalworking industry? We can tell you that, although lathes and milling machines can carry out drilling jobs, there is a special machine for this type of machining: the drilling machine.

Machining by drilling

If you are wondering what hole making is, you are probably familiar with it under its more common name: drilling. It is a type of machining by swarf removal, since the cutting tool, as it acts on the surface of the workpiece, removes part of the material in the form of small slivers called swarf.

The drilling principle is simple. The machine tool uses a cutting tool that rotates about its longitudinal axis while moving over the surface of the workpiece to be machined. The rotary movement is provided by a motor and transmitted to the tool through a gear and the chuck spindle. The feed movement followed by the tool can take different forms.

When a hammer drill is used, for example, the force, speed and intensity are controlled by the operator. When drilling is carried out by a machine tool such as the drilling machine, the lathe or the milling machine, it is the machine itself that controls the drilling unit. In both hand drills and industrial machines the workpiece stays fixed, while it is the head that performs the travelling and cutting movement.

What is metal drilling?

In conclusion, drilling is creating holes (of a certain diameter and depth) in the surface of a workpiece. To do so it is important to get specific tools such as drill bits or chucks that can be fitted to machines such as drills, milling machines and lathes. In addition to a suitable technique, choosing the best cutting tools is essential. Drill bits come in different sizes (thicknesses, lengths and diameters) and are matched to the needs of the workpiece to be machined.

How do you drill metal?

Metals are very hard, which makes them one of the most widely used materials for the manufacture of different parts. But metal has the drawback that it cannot always be handled easily; it all depends on the metal: stainless steel, iron, alloys, aluminium, etc. How do you drill metal properly?

Choosing the drill bit

Choosing the most suitable drill bit can be the key to successful drilling. It all depends on the type of metal to be worked, as not all drill bits are suitable for all metals. For example, high-speed steel (HSS) drill bits can drill almost all metals; the same goes for drill bits made of carbon steel that include a titanium nitride coating. For harder metals, the most advisable are drill bits made of cobalt steel.

In addition, using step drills can be ideal for drilling holes in sheet metal and thin materials. This type of drill bit makes clean holes of exactly the right size; it also makes it possible to drill holes of different diameters.

Holding the workpiece

Because of the power of the cutting tool, it can cause vibrations in the workpiece being machined and in the machine structure; as a result, the desired results may not be obtained. For this reason it is important that, before starting to drill, the workpiece is fixed on the worktable using any of the clamping systems such as the bench vice. This keeps the workpiece in place and makes drilling easier.

Marking the area

After positioning the metal, the specific point where the drilling is to be done must be marked. This can be done with a pencil or a pen, but it is important to be very precise. In the event of errors, it will be impossible to correct the drilled hole.

Some people choose to make a notch or mark on the surface. To do this you will need to use a punch or nail, as well as a hammer. When the drilling operation begins, the cutting tool will stay in place.

Constant pressure

Drilling requires suitable pressure to be carried out correctly. However, the pressure depends on the type of metal used; for hard metals, it is best to work at a slow, steady pace. When drilling soft metals it is possible to work at higher speeds.

Lubricating the drill bits

When drilling steel, experts recommend using cutting fluids or multipurpose oils. Lubricating the drill bits helps to reduce friction and heat build-up. This makes drilling easy and extends the service life of the cutting tools. When the metals are soft (aluminium, brass, etc.), lubrication will not be necessary.