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Glossary of terms

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Vinyl records break easily as they are made of a brittle material The brittleness of a material is a measure of how easily it will break and shatter, rather than stretching or compressing when stress forces are applied to it.

Cam out

Camming out, Exceeding the torque a  fastener head was designed  for can cause camming out. Cam out is when a driver such as a screwdriver bit slips/jumps out of a fastener head that is being driven. This is caused by the torque from the driver exceeding that which the fastener head was designed for.

Camming out will often damage the head of the fastener, in a similar way that rounding off can damage a bolt head. It can also cause damage to the screwdriver bit as well, so is something to be avoided wherever possible.

Clearance hole

The clearance hole is wider than the pilot hole so the screw threads do not catch on it as the screw passes through the first piece of wood A clearance hole is a hole drilled in the first layer of two pieces of wood you want to screw together. It is the width of the screw shank and allows the screw to pass through it.

A clearance hole is used to prevent the screw threads gripping the first piece of wood and pushing it away from the second piece as it continues through.


Corrosion of a bike light. This occurs when metal is left exposed to moisture. Corrosion is a reaction between a metal and the moisture in the atmosphere around it that degrades the metal, reducing its strength. The most common example is rusting.


Ductile materials can alter their shape without breaking Ductility is the ability of a material to change its shape, or stretch under tension without breaking.


The contact patch between rubber tyres of a bike and tarmac create high friction and a a gripy surface. Ice is a low friction slippery surface. Friction is a force that resists movement of objects that are in contact with each other. As the friction between two objects increases, movement between them becomes harder and requires more effort or energy.

Surfaces such as rubber generate a lot of friction which provides the grip for cars or bikes, whereas surfaces such as ice provide little friction or grip and are slippery..


Hard materials do not change their shape or scratch as easily as soft ones Hardness is a measure of how well a material resists scratching and changing its shape when a force is applied to it.


U.S. imperial measurement system compared to S.I. metric system The imperial system of measurement originates back to the time of the British empire, but is now most commonly used in the United States of America.


World map of countries that use the S.I. metric system of measurement Metric is a decimal system of measurement that was first introduced by the French, but is now the most commonly used system throughout the world.

Pilot hole

The clearance hole is wider than the pilot hole so the screw threads do not catch on it as the screw passes through the first piece of wood A pilot hole is a small hole drilled into a wooden workpiece into which a screw is tightened.

The purpose of a pilot hole is to remove some of the material from the wood and create space for the screw to occupy. By doing this, the screw puts less pressure into the wood and reduces the chance of it cracking or splitting the wood.


Workpiece being quenched by placing it in water Quenching is the process of rapidly cooling metal during manufacturing, often using water. It is done as part of heat treating to achieve desirable properties in the metal, such as strength and hardness.


Ratchet mechanism A ratchet is a mechanical system that allows motion in only one direction. Ratcheting socket wrenches are often simply referred to as ratchets and work by allowing the handle of the ratchet to swing in one direction, turning the socket, but do not turn the socket when the handle is swung in the opposite direction.


Rusty tool caused by exposure to moisture and oxygen in the atmosphere Rusting is a form of corrosion undergone by metals that contain iron. It occurs when such metals are left unprotected in the presence of oxygen and moisture in the atmosphere.


Torque is a turning force equal to distance from the centre of rotation multiplied by the perpendicular force applied Torque is a turning force. It can be calculated by multiplying the force applied by the distance along the length of the lever used to apply it. Torque can be calculated in either Newton meters (Nm) or Pounds feet (lbft).


Toughness test Toughness is the measure of a material’s ability to stretch or compress without breaking or shattering when a force is applied to it.