# Glossary of terms

Shop for Engineer’s Straight Edges

## Abrasion

Abrasion is the means by which an object can become scratched, scuffed, worn down or rubbed away.

## Bevel

A bevel placed on the edge of an object is an angled face that is not perpendicular to the other faces of the object. The blade of a knife is bevelled.

## Brittle

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.

## Burrs

Burrs are raised pieces of metal protruding from the surface of an object.

## Deflection

The deflection is a measure of how much an object is displaced (moves). This can either be under load, as in a load deflection, or under the object’s own weight, as in natural deflection.

## Ductile

Ductility is the ability of a material to change its shape, or stretch under tension without breaking.

## Hardness

Hardness is a measure of how well a material resists scratching and changing its shape when a force is applied to it.

## Micron

A micron or micrometre (µm) is a unit of measurement equal to one millionth of a metre or one thousandth of a millimetre.

## Parallel

When two surfaces or lines are an equal distance apart across their entire length.

## Quenching

Quenching is the process of rapidly cooling metal during manufacturing, often using water.

It’s done as part of heat treating to achieve desirable properties in the metal, such as strength and hardness.

## Rigidity

Rigidity or stiffness is the measure of an object’s ability to resist deflection or deformation of its shape when a force is applied to it.

## Rusting

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.

## Thermal expansion

Thermal expansion is the amount an object will increase or decrease in size as its temperature changes.

## Tolerance

The tolerances of an item are the acceptable errors in the physical dimensions of the item. No item is ever exactly to size, so tolerances are used to ensure a consistency of acceptable variation from the ideal size is achieved. For example, if a piece of wood was cut to be 1m long, it may actually be 1.001m. Or a millimetre (0.001m) longer in length than it was meant to be. If the tolerance for that piece of wood was ±0.001m then this would be acceptable. If however, the tolerance was  ±0.0005m then it would not be acceptable and would fail a quality test.

## Toughness

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