Swarf, which is the result of particles being removed when grinding hard or difficult-to-machine materials, tells a story. Many different abrasive types and abrasive grain sizes are applied to grind these materials.

Parts manufacturers choose precision abrasive grinding when other machining methods are not able to obtain the specified size, tolerance or surface finish. An abrasive grit or mesh is selected to achieve the required result.

Conventional and ceramic abrasives are called grit particles, whereas superabrasives are referred to as mesh particles. Both types of particles are screened and sized to achieve the appropriate sieve sizes.

Grinding hardened steel with an SG wheel produced this swarf. Image courtesy of Diamond Industrial Tools.com.

To determine the best abrasive size, end users must know the capabilities of the machine to be used. Workpiece material hardness and tolerance, surface finish and productivity requirements also play a role in choosing the correct abrasive size and type when grinding.

Swarf can help when choosing the type of abrasive grain used. Cast-iron swarf is in a powder form, which may require grinding with a green silicon-carbide abrasive. In contrast, grinding ceramics, glass and other crystalline materials require a diamond wheel because they are hard materials. Their swarf is a powder—not a curled chip.

Swarf tells additional tales: what the speeds and feeds are and how stiff and strong the grinding machine is. The color of swarf tells how effectively the wheel and workpiece are interfacing.

In addition, the condition of the swarf indicates how well the filtration system is doing its job, and material hardness influences the lubricity of the coolant chosen. Materials harder than 50 HRC, for example, require a more lubricious coolant. A good choice would be a 7:1 water-soluble solution or straight oil.

Always use your five senses when reviewing swarf. Save a swarf sample to show others who can help determine a method to boost productivity.