Since it is one of the tools More versatile and ubiquitous not only for the professional but also the hobbyist, the drill has been the subject of numerous articles in De Máquinas y Tools.
In this introduction we discuss the origins and various types of drills, from the simplest models to the most sophisticated and expensive. In addition, we expand the information on drills and other power tools, either corded or cordless and those of the pneumatic type. We focus on special models of electric drills, such as rotary hammers, screwdrivers, hammer drills and bench drills.
Since a drill uses a wide variety of bits and other accessory tools, we review all of them in this note and provide details on how to select them.
Later we provide a series of tips to correctly choose a drill, where we also describe the main components that we must know of this tool.
We also take care of the safety issues that are important to address whenever we handle a drill.
And finally we briefly describe what are the internal components of a drill, that is, those that are so important when cleaning, changing certain components or some simple repairs.
On this occasion, therefore, we are going to delve a little deeper into the anatomy of a drill, their main internal parts and the differences they present between various types of tool, such as between corded and cordless drills or drills with and without brushes.
What’s inside a drill?
Broadly speaking, a drill Electric is made up of a direct current motor made up of certain parts that are divided into two subsystems: one mechanical and the other electrical. The mechanical subsystem is made up of components such as the chuck or chuck, gears and bearings, and its purpose is to transfer, transfer or apply forces.
The electrical subsystem contains components, such as the brushes and the fan, that supply and control the flow of energy.
Some of these pieces are external and can be easily recognized in the figures in this article, where we can also review the details. In addition to the engine, other components are internal and now we are going to review them in greater detail.
For the sake of clarity we will consider the motor and other internal components separately from the drills with and without cable.
a) Corded drill
When we open the case of a drill with cable we find a series of pieces that we can appreciate step by step in the following video.
So, to summarize, although there may be slight differences depending on the manufacturer and model, a drill generic with cable presents the following exploded view:
- Chuck or chuck
- Right side housing
- Motor component: terminal base
- Motor component: stator unit
- Motor component: rotor unit
- Engine component: fan
- ON / OFF switch
- Motor component: carbon brush
- Electric cable
- Dust cover
- Tapping screw
- Left side housing
- Identification plate
The vast majority of corded drills use a universal motor with brushes, and here we can see the specific function performed by the internal components of this type of drills.
b) Cordless drill
Cordless drills are relatively simple devices, comprising a battery-powered unit and a DC motor that drives a dual-speed shaft and transmission, as well as a chuck. The electronics are relatively simple, providing an on / off function, typically both a forward and reverse gear configuration, and a speed control.
The great advantage of the technology of cordless drills is that they incorporate a brushless motor, so the internal anatomy of these tools It is simple and compact, as shown in the following parts breakdown diagram for a typical model.
- Left side housing
- Right side housing
- Screw for adjusting the housing
- Chuck screw
- Clutch selector
- Washer A
- Steel balls
- Plastic gear
- Washer B
- Steel gear
- Washer C
- Dc motor
- Rechargeable battery
- Switch for speed control
The battery is an essential component of any cordless tool, such as drills. In Machines and Tools we have also dealt extensively with this topic, not only introducing the various types of batteries, but also how to choose them, how to understand the importance of amperage and how to know about the performance of a battery.
With all of this knowledge in mind, let’s briefly review how a drill wireless.
In addition to their power supply, one of the big differences between corded and cordless drills is the type of DC motor they incorporate.
As we stated above, almost all corded drills have a universal motor, which means they can run on either alternating current (AC) or direct current (DC). However, most of these tools are configured to work on CA only.
In addition to the bearings and wiring, universal motors have two basic components: a rotor and a stator, as we saw in the video, and the exploded view of a corded drill. The rotor is the central part of the motor and is rotating, while the stator is the stationary component that surrounds the rotor. Both the rotor and stator contain field windings, which are electromagnets that activate when power is applied. It is precisely the magnetic fields of these electromagnets that make the motor work. The magnetic attraction pushes the rotor toward the opposing magnets of the stator, creating the torque and turning it. The electromagnets are activated sequentially by switching to maintain the rotation of the rotor and to adjust the speed and direction of rotation. Since the stator is fixed, it can receive power through a wired connection. But, since the rotor is rotating, the energy is supplied through conductive carbon brushes that run against the surface of the commutator. This switch is segmented, and the spaces between the segments create the intermittent contact that synchronizes and sequences the energization of the rotor electromagnets.
The mechanism is different when it comes to cordless tools, as power and space are key factors. Therefore, the stators of the brushed cordless models contain permanent magnets instead of windings, since the magnets are smaller and do not require power. These permanent magnet motors can be very efficient if they contain powerful rare earth magnets. Among the qualities of permanent magnet motors are good low speed torque and magnetic self-braking action.
However, brushless motor technology has gained ground and firmly established itself in cordless tools. A brushless motor is essentially an inverted permanent magnet motor – it has electromagnetic windings on the stator and permanent magnets on the rotor. Magnets do not require power, so there is no need for brushes or commutator.
Since it lacks the mechanical commutation provided by a rotary commutator, a brushless motor employs a microprocessor (a small built-in computer) to provide commutation in a process called electronic commutation. The position of the rotor is controlled by electronics, which synchronize the electrical pulses with the electromagnets in the rotor, thus controlling the direction and speed of the motor.
How does all of this translate to the internal anatomy of a brush motor and brushless drill? As shown in the following figure.
This is the reason why drills that have brushless motors are lighter and more compact, in addition to offering the qualities that we already know from this type of motor and a much easier maintenance than a traditional motor.
How to repair a drill
Now that we know its main internals, we can be in a position to take apart our drill and, with patience and a good hand, try simple repairs.
The following video will help us to find the possible faults and solutions of a drill With cable.
And in this other video we can learn to properly clean a drill cordless to extend the life of your components and your own tool.