Machinability is a property of a material, such as a metal, that makes it easy to drill, shape, cut, grind, etc. This term refers to the ease with which we can machine, such as metal. In this context, “to machine” means “to cut, drill, shape, etc.”
Materials with good machinability can be cut with relatively little power and at low cost. They can be cut quickly to easily get a beautiful finished product. Also, they don’t wear gear much. Most of the factors that improve a material’s performance are bad for its machinability. As a result, engineers have difficulty finding materials with relatively good machinability without sacrificing performance.
Collins Dictionary has the following definition of the term:
“Machinability of a material is its ability to be easily machined by a cutting tool.”
Predicting machinability is a challenge
The machining process has many variables, which can make it extremely difficult to predict how easily a material can be machined. Engineers focus on two groups of factors:
- Working material condition. This includes grain size, microstructure, chemical composition, hardness, yield strength, tensile strength and heat treatment.
- The physical properties of the working material. This includes the modulus of elasticity, thermal expansion, thermal conductivity and hardening.
According to Wikipedia:
“Other important factors are are the operating conditions, the material and shape of the cutting tool, as well as the parameters of the machining process.”
Percentage of a normalized value
We express machinability as a percentage of the normalized value. AISI has determined that AISI No. 1112 carbon steel has a machinability rate of 100%. AISI stands for American Iron and Steel Institute.
The Engineering Toolbox has a list of some common materials and their machinability against AISI number 1112.
No two materials are alike
Two materials to be machined cannot perform exactly the same when they are machined with the same tool, the same feed rate, the same cutting speed and using the same machine.
Some materials, such as mild steel, can produce long, curly chips. Cast iron, on the other hand, produces short chips.
One material may have a rough surface while another has a smooth surface. Others generate a lot of heat and quickly dull the tool.
