Why do we need so many grinding wheel types and grades?

When you need to grind something, your first question is what grinding wheel types are there and which suits my application the best?  Further, the term “grinding wheel” denotes something round, with rotation used for abrading a multitude of materials. This description is certainly very simplistic.  In fact, it becomes far more complex when selecting the grinding wheel type and grade to be applied for a specific application.

In general terms, the grinding wheel type refers to dimensions, shapes and profiles. Commonly known as the grinding wheel grade.

This has evolved over the last few decades in conjunction with numerous specialists in grinding machine tool construction and development, combined with the ever-increasing technical demands on the workpiece e.g. geometry, surface finish etc.

Stock to be removed, surface finish and tighter dimensional tolerances, for example, are all key factors in wheel grade selection. Certainly, we are now in the realms of high precision grinding.  Above all this requires considerable chemical and mechanical know-how to meet the requirements and to provide for economical production. Therefore, a full understanding and in-depth appreciation of application engineering, combined with a plethora of raw materials.  So methods of grinding wheel production are imperative for defining and formulating the grinding wheel grade.

Grinding wheel specifications

A grinding wheel specification is generally classified as a combination of grain type, grit size, hardness, porosity and bond. The basic grain types are aluminium oxide in its various forms and purity, and silicon carbide both extracted from natural resources i.e. bauxite and silica. For instance, the grit is sieved and graded into universal standard mesh sizes; these become the actual cutting edges in the grinding process, which can certainly be strong and tough or on the other hand very friable.

There are great benefits of using microcrystalline sintered aluminium oxide, also known as ceramic grain. Above all, benefits include high stock removal rates with reduced dressing frequency leading to shorter cycle times and longer grinding wheel life.

The combination of grit types and mesh size is a common practice for wheel grade selection for optimum grinding results. Firstly, Mesh sizes are available from 8 – 2000, 8 being very coarse used for fettling applications to 2000 for very high precision and superfinishing. Secondly, Finer mesh sizes produce finer surface finishes, improved geometry e.g. holding of radii, but result in a lower stock removal rate.

Having established which grain type to use which is dependent on the material to be ground (examples below), and the grit size which relates to stock removal and surface finish requirements, you are now able to decide which bonding system to use and then establish a suitable wheel hardness and structure; it is the percentage of grit and bond which determine wheel hardness and structure.

 

Surface grinding WHEEL TYPES

Workpiece Material Grinding wheel grade
Case hardened and normal tool steel, alloyed steel, hardened up to 63 Hrc White aluminium oxide, 46 grit, soft, vitrified bond
Over 63 Hrc White aluminium oxide, 46 grit, very soft, fairly open structure, vitrified bond

 

Profile grinding WHEEL TYPES

Workpiece Material Grinding wheel grade
Case hardened and normal tool steel, alloyed steel, hardened up to 63 Hrc Pink aluminium oxide, 60 grit, soft and open structure, vitrified bond
Over 63 Hrc Green silicon carbide, 100 grit, very soft and open structure, vitrified bond

 

Cylindrical grinding WHEEL TYPES

Workpiece Material Grinding wheel grade
Case hardened and normal tool steel, alloyed steel, hardened up to 63 Hrc Pink aluminium oxide, 60 grit, medium hardness and structure, vitrified bond
High-speed steel up to 63 Hrc White aluminium oxide, 60 grit, medium hardness and structure, vitrified bond
High speed steel over 63 Hrc Green silicon carbide, 60 grit, medium/soft hardness and medium structure, vitrified bond

 

* High-performance alternatives are available with a percentage of ceramic grain. These are often finer and harder due to grain characteristics.

We manufacture and supply various grinding wheels for many different applications including but not limited to:

Centreless (plunge and thrufeed)

Bar grinding

Internal grinding

Gear tooth grinding

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