Conductivity measures a material's ability to transfer heat or electric current. It is a physical property that guides the choice of metals and minerals used in precision mechanics, from measuring plates to control instruments.
What Is Conductivity
Conductivity is the property that describes how easily a material lets heat or electric charges pass through it. The term comes from the Latin conducere, «to lead, to bring together».
In physics there are two main forms: thermal conductivity, linked to the transport of heat, and electrical conductivity, linked to the flow of electrons. The opposite quantity is resistivity. Based on the extent of the transfer, materials are divided into conductors, semiconductors and insulators.
How Conductivity Works
The transfer depends on the carriers inside the material: free electrons and vibrations of the crystal lattice. In metals, free electrons move easily and carry both heat and electric charge, which is why copper and aluminium have high conductivity. In non-metallic materials, heat travels mainly through atomic vibrations, called phonons, with lower values.
Measurement follows two distinct quantities:
- Thermal conductivity, expressed in watts per metre kelvin, W/(m·K). It indicates the heat that crosses a unit thickness for each degree of temperature difference.
- Electrical conductivity, expressed in siemens per metre, S/m. It corresponds to the inverse of electrical resistivity.
Heat Conduction
Heat flows from hot areas towards cold ones until thermal equilibrium is reached. How fast the movement happens depends on the material's thermal conductivity: for example, a block of steel heats up and cools down quickly, while a block of granite stays "cold" longer because it lets heat through with difficulty.
Electrical Conduction
Electric current is the movement of electrons driven by an electrical "push", the potential difference. The better a material conducts, the less energy is lost as heat while the current passes through it. Copper is the reference metal, the best among those in common use; aluminium conducts a little less (about 60% compared to copper), but weighs much less and is cheaper.
Types of Conductivity
The forms of conductivity differ according to the type of quantity transported.
Thermal Conductivity
It describes the transport of heat through a solid, liquid or gaseous body. In precision mechanics it guides the choice of materials for plates and measuring instruments, where dimensional stability comes before dissipation.
Electrical Conductivity
It measures the passage of current through conductors. It is used in the selection of contacts and electromechanical components, as well as in non-destructive testing on metallic materials.
Ionic Conductivity
It concerns the transport of charge in solutions and electrolytes, where ions move rather than electrons. It is used in quality checks on water and process fluids, for example in the coolants of machine tools.
Why Conductivity Matters in Precision Mechanics
Thermal conductivity affects measurement accuracy more than one might think. Here are the reasons why it weighs on the choice of workshop materials:
- Dimensional stability: a material with low thermal conductivity, such as granite, reacts slowly to temperature swings and keeps its flatness over time.
- Lower sensitivity to hand heat: during use, a granite plate undergoes smaller deformations than a metal plate touched by the operator.
- Consistency with the reference temperature: at 20 °C the declared values remain valid; a stable material reduces deviations when the environment changes.
- Targeted dissipation, where needed: in components meant to dissipate heat, high-conductivity alloys such as aluminium and copper are chosen instead.
Applications and Sectors of Use
The conductivity of materials guides design decisions across various sectors: automotive, aerospace, packaging, railway, energy and machine tool manufacturers.
The table below collects the typical thermal conductivity values of workshop materials.
Material | Thermal conductivity (W/m·K) | Application notes |
|---|---|---|
Copper | ~400 | Among the best thermal and electrical conductors |
Aluminium (6000/7000 series) | ~210 | Lightweight, good heat dissipation |
Brass | ~110 | Copper-zinc alloy for mechanical components |
Carbon steel (C40) | ~50 | Structural and mechanical uses |
Cast iron | ~50 | Stability and good vibration damping |
Stainless steel (X5CrNi18-10) | ~15 | Low conductivity, corrosion-resistant |
Granite | ~2.5–3.5 | High thermal stability, ideal for measuring plates |
In precision mechanical workshops, granite is often chosen when stability matters: dressing plates and granite surface plates use the material's low thermal conductivity to keep flatness during dimensional checks. Steel and cast iron remain the basis for clamping plates, squares and cubes, where mechanical robustness is required. Aluminium and copper come into play instead where the project calls for heat dissipation.
The practical difference shows up in the quality department. A metal plate exposed to a heat source (a nearby machine, solar radiation, prolonged contact with the operator) develops thermal gradients and deforms by a few microns, enough to distort an inspection on tight tolerances. Granite, with a conductivity twenty times lower than steel, reduces such an effect and keeps the reference surface within the declared flatness grades.
Advantages of Conductivity
Conductivity becomes an advantage when its value matches the function of the component.
High thermal conductivity, typical of copper and aluminium, dissipates excess heat quickly and protects parts from overheating; high electrical conductivity reduces losses through the Joule effect and cuts energy waste along conductors and contacts.
On the opposite side, low conductivity becomes an asset where stability matters, because it slows the response to temperature swings and preserves the geometry of precision parts, as well as acting as a barrier where thermal or electrical insulation is needed. The comparison between thermal and electrical conductivity values thus steers the choice of material towards the required performance, from the heat sink to the measuring plate.