About 80% of the known chemical elements are metals.
- Metals are opaque lustrous elemental chemical substances that are good conductors of heat and electricity and, when polished, are good reflectors of light.
- Most elemental metals are malleable, ductile, and are generally denser than the other elemental substances.
- Metals are structurally distinguished from nonmetals by their atomic bonding and electron availability.
- The electron band structure of metals is characterized by a partially filled valence band. The “free electrons” lost from the outer shells of metallic atoms are available to carry an electric current.
- The defining property of a metal is that it is an element with a positive thermal coefficient of resistivity, meaning the electrical resistivity of a metal continuously increases as temperature increases.
Types: There are a number of different grades that have some significantly different properties and machining qualities. Aluminium also forms a number of different alloys.
Parting Aluminium on the lathe can be tricky, so some simple rules to make this easier.
Types: Brass is an alloy of copper and zinc, but often other elements such as aluminium, iron, manganese, tin and lead are added. The result is a number of different types, standards and historical descriptions of brass.
With its low melting point, good fluidity, castability, excellent machinability and wear resistance, cast irons have become an engineering material with a wide range of applications, including pipes, machine and car parts. There are a few worthwhile hints and tips when machining cast iron.
Noted for being ductile and having good electrical and thermal conductivity. It forms the basis of a number of alloys e.g. brass and bronze.
C101 – High conductivity – used in the electrical/electronic component industries.
C106 – available in sheet & strip in coil and tube it has excellent welding properties. It also can be offered in highly polished finishes for architectural purposes.
Used a lot for cutting tools.
The image to the right shows some blank pieces ready to be ground to shape and then used as lathe cutting tools.
A single throw crankshaft machined from mild steel.
Hardening: Mild steel can be case hardened to increase the surface hardness. Case hardening can be difficult to get hold of, but EKP Supplies Beta 1 compound.
Traditionally an alloy containing 80% tin and 20% lead.
The image shows a pewter flywheel on a solenoid engine. The outer surface has a hammered finish.
There are a lot of uses for silver steel and a lot of these are because it is easy to harden. Also, silver steel is readily available in both metric and imperial round bar that is very accurate and so great for axles. Cutting speeds for silver steel, these are just an indication but they are a good starting point.
Nowadays tools are often referred to as being made from “carbide” – what they actually mean is Tungsten Carbide. The reason for using Tungsten Carbide is it has some great properties:
melting point 2,785–2,830°C
hardness of 9 on Mohs scale, 2600 Vickers number
Some tungsten carbide tools consist of a mild steel shank with a piece of tugsten carbide brazed in place and then ground to shape.