The 7 Factors Used to Determine a Grinding Wheel Specification (2024)

Dave Goetz, Corporate Application Engineer, Norton | Saint-Gobain Abrasives

How to Choose a Grinding Wheel

Many of us have used grinding wheels as part of our regular, daily work functions, but most of us don’t know why we use the wheel we do, or even if the wheel we are using the right one for the job.

There are many different types of abrasive grains, available in a whole range of grit sizes and held together by different bonding agents. How do we know which to use?

It's simpler than we might think. A grinding operation is a system, and as a whole, there are many parts to consider. One key component is the wheel. To determine where to start, consider the seven operational factors.

1. The Material Being Ground
2. The Severity of the Operation
3. Required Finish and Form Accuracy
4. Area of Contact
5. Wheel Speed
6. Coolant Use
7. Machine/Spindle Horsepower

By taking each of these seven factors into consideration, it is possible to narrow the field down to a smaller list of options to start with for any grinding operation.

1. The Material Being Ground

The first thing to consider when selecting a grinding wheel specification is what are we grinding? What is the material, and how hard is it? Is it easy to grind or difficult? By reviewing these elements, we can select the correct abrasive type, the grain’s attributes, the appropriate grit size, and bond type.

Knowing the properties of the material we are working with helps us select the proper abrasive grain and its attributes. By convention, we use aluminum oxide grains for grinding ferrous metals and silicon carbide for non-metals and non-ferrous metals. Ceramic and superabrasive grains can be used on either but generally under specific circumstances where the material being ground requires these types of grains or when we are looking to optimize process performance.

Once we know which grain type to start with, we can look at the material grindability. If the material is easy to grind, we will want to use a tough/durable grain. Since the material is easy to grind, the grain shouldn’t break down too soon or too easily, so the whole grain can be used to maximize wheel life. For materials that are hard to grind, we will want to use a mild/friable grain, which fractures more easily, stays sharper, and actually grinds the material.

For easy to grind materials, we would want a coarser grit. This is because the grain can easily penetrate the material, make and remove chips. Using a larger or coarser grit maximizes the stock removal, reducing cycle time.

Another aspect of the wheel we can dial in on based on the material being ground is the grade or hardness of the bond. If the material is considered easy to grind, we can use a harder grade, which ensures that the wheel doesn’t release the grain before it is consumed. Knowing that we want to use the abrasive grain for as long as we can, we want the bond to hold that grain in the wheel for as long as possible.

If the material is difficult or hard to grind and we use a blocky, tough, and durable grain, we run the risk of simply dulling the grain and opening the door to finish issues, such as burning, because the grain will rub and not grind.

The material being ground also helps us determine the grit size. For hard to grind materials, we would recommend a finer grit size because a smaller particle will penetrate hard materials and form a chip easier than a larger blockier one. Difficult or hard to grind materials are abusive to the abrasive grain and can cause them to blunt or dull. Since we need more sharp points to penetrate the material, we want to ensure the grains are being released before they become too dull and cause metallurgical damage. With hard materials, a softer grade should be used so that the material is constantly being exposed to sharp grains. The grade needs to be soft enough to release the dulled grains and keep exposing new sharper grains to the work.

2. The Severity of the Operation

Here we consider how much or how heavy the grinding pressure will be in the grind zone. The higher the grinding pressure or force per grain, the more severe the operation. It is operations like these where today’s ceramic and superabrasive grains do well. Much like the material we are grinding, severity of operation helps us determine the attributes of the abrasive grain.