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Power Tool Accessories.

Drill Terminology

Types of drill

Twist drills

The twist drill bit is the type produced in the largest quantity today.

The twist drill was invented by Steven A Morse of Massachusetts in 1861. The original method of manufacture was to cut two grooves in opposite sides of a round bar, then to twist the bar to produce the helical flutes. This gave the tool its name. Nowadays, the flutes are more usually formed either in a forging process called roll forging, or in a machining/grinding process.

Hammer/Percussion/Impact drills

You will often hear the term rotary hammer, percussion or impact drill – but what are they and what is the difference?


Firstly, they are all terms used for different types of electric drill, not the drill bit. And secondly they are all designed for use on drilling through brick, stone and concrete materials – Masonry.

A percussion or impact drill (both terms are used for the same type of drill) securely holds a straight shank drill bit in its chuck and the whole chuck and drill bit assembly vibrates when the drill is being used – it’s this action that causes the tip of the drill to pulverize the masonry as it turns making drilling much easier.


There is a mechanism sat behind the drill chuck that causes this movement – it is usually two serrated surfaces that bounce over each other as the chuck turns. It can usually be switched on or off depending on what is being drilled.

A rotary hammer drill has a slightly different action – the bit is loosely held in the chuck and while the bit is turned, a mechanism strikes the end of the drill bit.


This requires a drill bit with a special shank and is covered in much more detail in the next section about drill shanks.

Long series drills

Does what it says on the tin - extended length twist drills for deeper holes.

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