Introduction

Cordless drills are versatile, durable tools that can be found on construction sites, in garages and shops everywhere. One of the things that makes cordless drills so popular is that they can be taken almost anywhere. Just make sure that you have a fully charged battery and spare if you plan on working late. Cordless drills have almost (but not completely) replaced the old corded models.

 

The Power Supply

The most common power pack in a cordless drill--or even most cordless tools for that matter is the nickel cadmium (NiCd) battery. A battery is generally made up of two dissimilar metals (in this case nickel oxide hydroxide and cadmium) in an electrolyte ("battery acid"). In a battery, the chemical reaction between the two metals and the electrolyte cause electrons to flow from one side to the other.

In a cordless drill, the NiCd battery supplies current to a small DC motor which does the work of the drill.

 

The Work Horse

In any electric motor, there will be an armature (also called a rotor), a commutator, brushes, a permanent magnet and an axle. When direct current is applied to a DC motor, it creates an electromagnetic field in the windings of the armature. The difference in magnetic forces between the armature and the permanent magnet cause the armature to turn. As the armature turns, the commutator acts as a switch that reverses the current in the armature (and the brush connects the commutator to the current). This reversal of current keeps the armature turning.

 

The armature turns the axle and in a cordless drill the axle turns a transmission. The transmission has several gears that turn the spindle that does the actual drilling action.

 

 

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