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00:00This is a cordless drill. In this video, we'll take a close look at the mechanism inside to see
00:05how it works. Before we jump into the inner workings of a cordless drill, let's first look
00:10at the key components involved. Let's get started. Cordless drills are one of the most common and
00:17versatile power tools available. They convert electrical energy into torque and are mainly
00:22used for drilling holes and driving screws. This is the chuck. It's a self-centering,
00:28three-jaw clamp that holds the drill bit securely in place while it's spinning. Most cordless drills
00:35use a keyless chuck that is hand tightened by simply gripping and rotating the outer sleeve.
00:41A clockwise turn tightens the chuck and a counterclockwise turn releases the bit.
00:46The chuck size on cordless drills is generally 10 or 13 millimeters. This is the clutch collar that
00:54lets you adjust the drill output torque settings by simply turning the collar.
00:58The main purpose of the clutch is to keep you from overdriving screws and avoid cam out.
01:03The clutch collar has printed numbers all around. The higher the number in line with the arrow,
01:09the higher the torque setting. There is also a drill mode represented by a drill icon,
01:14which is the highest torque setting. When the drill torque reaches a predetermined setting,
01:19the clutch will slip and the bit will stop spinning. Lower torque settings are suitable for driving
01:25screws into softer materials, while higher settings are for harder materials.
01:33This is the gear switch. Typically, drills are equipped with the gear switch,
01:37allowing you to switch between low and high speed settings. In the low speed setting,
01:42the drill operates at a higher torque, which is used for tasks like driving screws.
01:48In the higher speed setting, the drill operates at a lower torque, which is suitable for drilling holes.
01:55This is the trigger switch to operate the drill. Most drills have a variable speed trigger,
02:00meaning the more the trigger is pressed in, the higher the speed of the drill's chuck.
02:07Just above the trigger switch is the forward-reverse switch,
02:10that slides in and out to change the direction of rotation of the drill bit.
02:15This is the rechargeable and removable battery that powers the drill. Today's coreless drills use
02:22lithium-ion batteries. They are specced according to two main characteristics, voltage and charge capacity.
02:29Battery voltages for coreless drills commonly range between 12 and 20 volts. Generally,
02:35higher voltage indicates a more powerful tool. The charge capacity is measured in amp hours,
02:40and it refers to the amount of energy the battery can store and provide over time. A higher amp hours
02:47rating generally means longer run time, but batteries tend to be physically larger. The charge capacity of
02:54coreless drill batteries usually falls within the range of 2 to 10 amp hours.
03:00The inside of each battery contains a group of individual cells wired together,
03:06which look like AA batteries, but larger in size. One of the most common lithium-ion cell types is the
03:1218650 cell. The name derives from the cell's dimensions, with a diameter of 18 millimeters and a
03:19length of 65 millimeters. The nominal voltage of each 18650 cell is 3.7 volts, with a maximum charging voltage of
03:294.2 volts when fully charged. Adding more cells in series will increase the battery voltage by roughly 4 volts,
03:37and connecting them in parallel will increase the battery charge capacity. In this example,
03:42we have a 12-volt battery that contains three 18650 cells wired in series. Inside the battery housing,
03:50a printed circuit board manages critical functions like charging and discharging, ensuring the safe
03:56operation of the battery pack. Now let's take a look inside the coreless drill. This is the trigger
04:03switch assembly. Inside, there is a printed circuit board that increases the motor voltage the deeper
04:09the trigger is pressed in. The higher the input voltage of a motor, the faster the output speed.
04:15When you release the trigger, a spring pushes back the trigger to its default position,
04:20and the chuck stops rotating. When sliding the forward-reverse switch in and out, it operates a
04:27small lever connected to a rotary switch. This switch changes the polarity of the motor circuit, thereby
04:34altering the rotation direction of the motor. Setting the switch in the forward position will drive the
04:40chuck clockwise, while setting the switch in the reverse position will drive the chuck counterclockwise.
04:46There is also a center position to lock the trigger switch. This is the electrical motor that converts
04:52the electrical energy from the battery into mechanical energy. The electric motor is directly connected
04:58to a gearbox that transfers the motor power to the chuck, while increasing its torque and reducing speed.
05:05The gearbox comprises three sets of planetary gear stages, connected in series. Each planetary stage
05:13consists of four main components. The sun gear, three or more planet gears, the planet carrier,
05:20and the ring gear. The sun gear of the first planetary gear stage is connected to the motor shaft.
05:25When it turns, it moves the planet gears that roll along the inside of the fixed ring gear.
05:31The planet gears are mounted on the carrier. Their rotation causes the carrier to spin at a lower speed
05:37than the sun gear. The back face of the planet carrier has a gear that acts as the sun gear for the next
05:44planetary gear stage. The output of one stage becomes the input for the next.
05:52Let's now understand how the gear switching mechanism works.
05:56The gear switch is connected to a shift arm that moves the ring gear of the second planetary gear stage
06:02to the position corresponding to the desired speed setting.
06:08When the second stage ring gear is positioned at the high speed setting,
06:11the planet gears and the external gear teeth on the carrier both engage simultaneously with the
06:17internal gear teeth of the ring gear. This locks the carrier and planet gears together,
06:23connecting the input and output elements together, bypassing the second planetary gear stage,
06:29lowering the overall gearbox ratio, resulting in a higher output speed and lower output torque.
06:37When the second stage ring gear is positioned at the low speed setting, the external teeth of the ring
06:42gear engage with internal teeth of the first stage fixed ring gear. This locks the second stage ring gear
06:49in place, enabling the second planetary gear stage, increasing the overall gearbox ratio, resulting in a lower
06:57output speed and higher output torque. Now let's see how the clutch mechanism works.
07:03Inside the clutch collar, there's a spring-loaded plate, pushing against steel balls that engage with notches
07:10on the back face of the third stage ring gear. When you turn the clutch collar to adjust the torque setting,
07:16you are essentially compressing or releasing the spring. This increases or decreases the pressure applied by the plate on the steel balls.
07:23When the drive torque exceeds the preset limit, the spring force is overcome and the balls roll out of their notches,
07:31allowing the planet gears of the third stage to turn the outer ring. This action keeps the planet carrier stationary,
07:38stopping the bit from turning. The ratcheting sound you hear when the clutch engages is produced by the ball rolling
07:44against the notches on the ring gear. Finally, let's take a look inside the chuck. Inside the chuck,
07:52there's a threaded nut attached to the outer sleeve that mates with threads on the jaws. The outer sleeve
07:58rotation translates into an axial movement of each jaw, moving the jaw forward and inward on a slight angle,
08:05clamping down on the drill bit. I hope you found this video informative and interesting. If you did,
08:11don't forget to give it a thumbs up and subscribe.