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Diamond disc for angle grinder - principle of operation
What happens when cutting with a diamond blade? When you know the principle of operation, it will save you a lot of money and disappointment. It will be easier for you to find your way when buying the right wheel for your specific requirements and you will also get help when cutting specific materials for which you cannot find a diamond cutting wheel.
Construction of a diamond wheel for an angle grinder
fig. 1 Agressa diamond disc 125 mm - Disc body (1), centre hole (2), unique serial number (3), cutting part of the blade - diamond segments (4)
A diamond cutting disc is a flat circle with a hole in the center and a cutting part around the circumference of the disc. The cutting part can have different shape, height and thickness and is made by mixing binder and synthetic diamond grains.
The concentration and size of the synthetic diamond grains, as well as the composition of the binder, determine the "quality" of the diamond wheel.
What do we mean by the quality of the diamond wheel?
From the user's point of view, a diamond blade is of high quality when it cuts quickly, cleanly and lasts indefinitely. And maybe it would be good if it didn't create dust when cutting, it would be usable for different materials and more...
No such disc exists.
All manufacturers balance between conflicting requirements and the result is always compromise solutions. However, to better understand them, we need to explain why a diamond blade cuts.
Principle of operation of the diamond wheel
In the cutting part of the disc - around its circumference - there are sharp and hard diamond grains connected by a binder made of a special metal.
The principle of operation of the diamond wheel is the gradual grinding of the contact surface to dust due to the frictional force of the diamond surfaces at high peripheral speed.
In other words, and simply put, diamond grains grind the cut material and turn everything in their path into a fine dust. It is worth noting here that the use of a respirator when dry cutting is not a formality, but a necessity.
Although the diamond grains are sharp and very hard, they become dull during work. Nothing lasts forever. In this phase, the binder plays a key role – the diamond tool must get rid of the dull grains of the synthetic diamond in time. The key word is "on time".
fig. 2 Macro photograph of a segment of the Agress diamond wheel
fig. 3 Usain Bolt takes the baton at full speed in the 4x100m final at the 2017 World Championships in Athletics
It is something similar to a relay race. A runner who is catching up has a defined part of the track to pass the baton to another runner. Within it, both runners must be coordinated at full speed in order not to lose valuable hundredths of a second. The baton must be passed on time - not earlier, not later. On time. Speed is not enough, accurate passing of the baton is the result of hard training.
It is the same with diamond grains.
It is not enough that they are very hard, very sharp and large enough. This is indeed a necessity for a good diamond wheel, but only in connection with a suitable binder will the efficiency of the system be fully demonstrated.
When the binder loosens the grains too early, the blade may cut quickly, but it wears quickly and therefore has a shorter life.
Otherwise - when the binder releases the grains too slowly - they remain as worn and dull "in their places" for too long. As a result, the blade cuts slowly, the work goes hard, but the service life is longer.
The timely release of the blunt diamond grain is the main role of the binder.
The connection between the bond of the diamond wheel and the cut material
The range of cut material for which we are looking for a disc is wide - granite, marble, tiles, tiles, concrete, reinforced concrete...
The hardness of these materials is different - therefore the binder must also be different. The principle applies that to cut hard material we need a diamond cutting wheel with a soft bond and vice versa. Asphalt is soft, so it requires a hard binder, cured concrete is hard, so a soft binder.
However, in practice it is not so simple. For example, concretes are of different composition, strength, with different gravel admixtures, with and without steel reinforcement, and even with different homogeneity. All of this complicates things a bit.
fig. 4 Variety of building materials
When we talk about homogeneity, for example, a typical example is granite - a deep igneous rock. (Almost) all granite deposits are homogeneous, but their composition is different. In such cases, many times the "correct" binder is searched for in order to make the cutting as efficient as possible in the given material. It is therefore a special production of the diamond wheel most suitable for the given granite.
In the case of angle grinder discs, it is important to design the optimal bond to suit the majority of materials that will be cut with the diamond disc.
Conclusion:
Let's not be mistaken by saying that discs for hard material will definitely be good for soft materials as well. Discs for hard materials have a soft bond and are only suitable for hard materials. However, it is always true that the disc you are currently holding in your hand is certainly suitable not only for the materials that are written on its packaging, but for all materials of similar hardness. The question is the cleanliness of the cut - but that's a topic for another article.
Sources:
HERMAN internal technical and training materials
www.thequint.com/sports/olympic-sports/usain-bolt-farewell-race-qualifying-time
www.freepik.com/free-photo/bricklayer-worker-installing-brick-masonry-exterior-wall-with-trowel-putty-knife_4550498.htm
Ing. Herman Nagypál
I graduated from a military school. I learned to work with tools and equipment as a child with my father on the construction of our family house. I test each of our new products personally - with my own hands in my well-equipped workshop. In my spare time, I study trends in the field and like to try competitive products. Some of them make me laugh, and some of them make me wonder (that someone got caught and bought it), but some are really good. Almost like ours 😊.
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