![Drill Case Drill Case](http://www.experimental-engineering.co.uk/wp-content/uploads/2010/10/GEDC0133-300x225.jpg)
Here is a Bosch 14.4v Professional cordless drill/driver, recovered from a skip!
It was thrown away due to a gearbox fault, which was easy to rectify.
![Internals Internals](http://www.experimental-engineering.co.uk/wp-content/uploads/2010/10/GEDC0134-300x225.jpg)
Here is the drill with the side cover removed, showing it’s internal parts. The speed controller is below the motor & gearbox here. The unit at the top consists of a 12v DC motor, coupled to a 4-stage epicyclic gearbox unit, from which can be selected 2 different ratios, by way of the lever in the centre of the box. This disables one of the gear stages. There is a torque control clutch at the chuck end of the gearbox, this was faulty when found.
![Motor Motor](http://www.experimental-engineering.co.uk/wp-content/uploads/2010/10/GEDC0135-300x225.jpg)
Here is the drive motor disconnected from the gearbox, having a bayonet fitting on the drive end.
![Drive Gear Drive Gear](http://www.experimental-engineering.co.uk/wp-content/uploads/2010/10/GEDC0136-300x225.jpg)
This is the primary drive gear of the motor, which connects with the gearbox.
![Cooling Fan Cooling Fan](http://www.experimental-engineering.co.uk/wp-content/uploads/2010/10/GEDC0137-300x225.jpg)
The motor is cooled by this fan inside next to the commutator, drawing air over the windings.
![Gearbox Gearbox](http://www.experimental-engineering.co.uk/wp-content/uploads/2010/10/GEDC0138-300x225.jpg)
This is the gearbox partially disassembled, showing the 1st & second stages of the geartrain. The second stage provides the 2 different drive ratios by having the annulus slide over the entire gearset, disabling it entirely, in high gear. The annulus gears are a potential weak point in this gearbox, as they are made from plastic, with all other gears being made of steel.
![Charger Charger](http://www.experimental-engineering.co.uk/wp-content/uploads/2010/10/Charger-300x225.jpg)
Here is the charging unit for the Ni-Cd battery packs supplied with the drill. The only indicator is the LED shown here on the front of the unit, which flashes while charging, & comes on solid when charging is complete. Charge termination is by way of temperature monitoring.
![Transformer Transformer](http://www.experimental-engineering.co.uk/wp-content/uploads/2010/10/GEDC0142-300x225.jpg)
Here the bottom of the charger has been removed, showing the internal parts. An 18v transformer supplies power to the charger PCB on the left.
![Charger PCB Charger PCB](http://www.experimental-engineering.co.uk/wp-content/uploads/2010/10/GEDC0141-300x225.jpg)
This is the charger PCB, with a ST Microelectronics controller IC marked 6HKB07501758. I cannot find any information about this chip.
![Battery Pack Internals Battery Pack Internals](http://www.experimental-engineering.co.uk/wp-content/uploads/2010/10/GEDC0143-300x225.jpg)
Here is a battery pack with the top removed, showing the cells.
![Temperature Sensor Temperature Sensor](http://www.experimental-engineering.co.uk/wp-content/uploads/2010/10/GEDC0146-300x225.jpg)
This is the temperature sensor embedded inside the battery pack that is used by the charger to determine when charging is complete.