You might think that a grinding wheel is a simple cutting tool. There is not much more to it. Think again.
Yes, a grinding wheel is a cutting tool but it can be made from multiple materials and be subject to many other factors. These various parameters have been extensively studied by engineers and scientists.
Grinding wheels have been important in manufacturing for over 150 years. Over that time the material, design, and geometry have been refined for specific applications. Grinding wheels continue to be a fundamental tool in the aviation industry.
That means one size does not fit all. Choose the wrong grinding wheel and it could be disastrous for your product or at the very least waste time and money. This is your guide on how to choose the right grinding wheel for your shop.
Grinding Wheel Anatomy
Every grinding wheel has some basic anatomy. It is constructed from abrasive grains that actually do the cutting and also a bonding agent that holds it all together. The volume of grains or their density and the strength of the bonding are basic variables that determine the make-up of the grinding wheel.
More About Abrasive Grains
These grains have sharp edges to them a little bit like the teeth in a traditional saw. As the grain cuts against the work surface, they will eventually dull. At some point, the grain will fracture and then create new cutting edges.
The best abrasive grain is one that will dull at the slowest rate while still providing the desired effect on the work surface. Obviously, as the work surface or product material varies so does the best or most effective grain type.
The shape and size of the grinding wheel is another subject in itself. However, the size of the individual grains is an important variable in considering the function of the grinding wheel.
Grains are sized using a sort of screen or filter that has many holes in the surface and through which the individual grains pass through. If the screen has a low number of holes per inch then the grains are larger. If the screen has a high number of holes per inch then the grains passing through these gaps are smaller.
So in essence, high numbers (70 upwards) mean small grain sizes and low numbers (24 downwards) mean big grain sizes.
Larger grains are useful for more course work where a smooth or fine finish is not so important. The grain sizes are much smaller for smoothing and polishing. This is the same basic principle when choosing sandpaper with woodwork.
What Grinding Material Should I Use?
The first thing to know when choosing a material is that most manufacturers have a number reference that you can use to match to the material you will be cutting.
Please note that these references may not be the same between manufacturers. It may not be enough to simply know the basic material of the grinding wheel when matching it to your product material.
For example, one of the most common materials is Aluminium Oxide. It is suitable for grinding wrought iron, bronzes, carbon steel, and alloy steel. However, there are many different blends with Aluminium Oxide specifically crafted to suit a specific material.
Zirconia Alumina is another fairly common example. It is a strong, tough material well suited to rough cutting applications like in the construction industry. The development of abrasive materials is ongoing.
Some innovations include materials that have a controlled fracture point so that the wheel is basically self-sharpening while retaining a high degree of accuracy.
Keeping It All Together
The right abrasive material must be matched with the correct bond for a particular application. These two variables go hand and hand.
As the grains wear down, dull and fracture and further diminish they lose their utility. The bond that holds it all together must also wear down at the same rate so that when the grains are consumed, they can simply fall away with the worn bonding material.
That in itself is a work of science and engineering. The strength of the bonding material is said to be a hard grade or soft grade. Hard grade means the bond is strong and will hold the wheel together under great force and pressure.
In contrast, the soft grade gives a weaker hold to the grains. This means they will drop away from the grinding wheel much more easily. Bond grade and grain size and material are matched for specific applications.
The fusion of grains and bond usually goes through a vitrifying process with the application of high temperatures. Other bond materials are organic like rubber, and a resin is another example.
Resin bond diamond wheels are used for fine finished on a variety of materials. Read more now if you want to use this type of grinding wheel.
Grinding Wheel Geometry – Get into Shape
The basic principle shape is about delivering the most effective cutting surface to whatever material you are working on. A straight cutting edge is the most common application.
There are various other shapes including a recessed or hollow edge. The design is such, to allow you to apply the force of the grinding wheel to awkward or difficult to access surfaces.
No Need to Re-Invent the Wheel
This article has helped you understand some of the basics of a grinding wheel and how to choose the right one for your shop.
Do not be overwhelmed by the vast array of choices. You are not the first or the last person to be surprised how sophisticated grinding wheels are. Whenever you are going to do a job make sure you consult the manufacturer’s guide and take into account the principles in this article.
You can read many more articles on our website that serve all sorts of industries. For example, if you work in the plumbing industry you will be interested in this link here.