Cutting Efficiency is normally expressed as how much area the diamond saw blade can cut in unit time. It indicates the sharpness of the blade. This is the criterion that users should first consider. The blade’s sharpness should meet the user’s cutting efficiency requirement. Generally, using coarser diamond grit or/and lower diamond concentration can improve the sharpness of the blade.

Service Life is normally measured with the total area the diamond blade can cut. When a certain specification of material is cut, this criterion can be also expressed how long the blade can cut. It indicates the durability of the blade. When the user is satisfied with the blade’s cutting efficiency, its service life should then be paid attention to. Generally, adopting higher diamond concentration or/and finer diamond grit can prolong the blade’s service life.

Processing Quality here means the quality of the cutting on the material. This criterion mainly includes the flatness and roughness of the cutting surface, the parallelism of the two cutting sides, and the integrity of the edges.

Diamond grit determines the number of diamonds per carat. The finer is the grit, the more diamonds are there per carat. When the diamond concentration is certain, finer grit means more diamonds on the cutting surface of the diamond saw blade. So finer grit can improve the blade’s service life, but will also increase the power consumption of the saw machine.

Coarse diamond grit is suitable for cutting soft materials, and fine diamond grit is suitable for hard materials, because smaller diamonds are more easily to cut into hard materials.

Diamond concentration greatly influences the performance of a diamond saw blade. If the concentration is too low or too high, the ideal cutting result will not be got. The commonly adopted concentration is between 25% and 75%. Generally, when the concentration increases, the diamond blade’s sharpness and cutting efficiency drop, while its service life increases. So when high cutting efficiency is required and the cutting roughness requirement is not high, diamond blades with low diamond concentration and coarse diamond grit are popular.

Diamond concentration also influences the power consumption of the saw machine. When the concentration increases, the power consumption also increases.

1. Wholly Sintered Diamond Saw Blades

Wholly sintered diamond blades are made by putting the steel cores along with diamonds and metal bond materials into molds, and then sintering them in sintering machines. Blades of this type are often referred to just as sintered diamond blades. Normally, their diameter is no bigger than 400 mm. One of the reasons maybe is for the limitation of the size of the sintering machines.

Generally, the main steps in making sintered diamond blades are: First, put the steel cores, diamonds and metal bond materials into high-strength steel molds. Second, put the molds into a press machine to press them to form the blanks without heating. Third, take out the blanks from the steel molds and examine the blanks. Fourth, put the blanks into graphite or stainless-steel molds. Fifth, put the molds into a sintering machine and sinter them to produce the diamond blades.

In the above fifth step, there are many types of sintering machines which can be chosen. Some sintering machines can exert pressure on the blanks during the sintering process. This can make the diamond segments of the blade be well alloyed, and the segments’ density is high. The produced blades are normally called hot-pressed diamond blades. These blades have a longer service life. However, some sintering machines cannot exert pressure on the blanks when sintering. The produced blades are normally called cold-pressed diamond blades. These blades’ diamond segments’ density is low and porosity is high. This can improve the cooling condition when the blades are being used, but will also lead to a shorter service life.

Sintered diamond blades can be used to cut granite, marble, concrete, asphalt, ceramics and many other building materials. Some of them can only be used in wet cutting (e.g. continuous rim diamond blades), while some of them can be used in both wet and dry cutting (e.g. segmented diamond blades, turbo diamond blades and turbo wave diamond blades).

In making sintered diamond blades, the steel cores are also put into molds and sintered. So the diamond blades can be produced in bulk, and the production output is high. But also for this reason, the steel cores cannot be quenched, so their hardness and toughness are not high, and so the steel cores may deform in high-load and high-intensity cutting processes. Therefore, in some cases sinter diamond blades’ cutting efficiency cannot be very high.

2. Silver Brazed and Laser Welded Diamond Saw Blades

When silver brazed or laser welded diamond blades are made, the diamond segments on the blades need to be firstly produced. Normally, the method for making these diamond segments is hot pressing, and is similar to the method used to make the sintered diamond blades, while there is no the steel core’s participating. When the diamond segments are available, they are silver brazed or laser welded onto the steel cores to form silver brazed diamond blades or laser welded diamond blades.

Silver brazed diamond blades’ diamond segments do not necessarily need a transition layer. They are brazed to the steel cores via silver-based brazing films which normally contain 40% – 50% silver. The connection between the diamond segment and the steel core depends on the melted and penetrated silver solder, so the connection strength is not very high (normally, its bending strength is 350 – 600 MPa). Silver brazed diamond blades can only be used in wet cutting, because if they are used in dry cutting, the high temperature generated in the dry cutting can cause the silver solder to be melted, and the diamond segments may fall off the blade and fly out and may hurt the operator.

Laser welded diamond blades, however, have many advantages. Laser welding is a kind of fusion welding. It causes the junction of the diamond segment and the steel core to be melted and then form a metallurgical connection. The depth-width ratio of the weld is high, which can reach 5:1 or even 10:1. So the connection strength is high and the bending strength can reach 1800 MPa. Qualified laser welded diamond blades can be used in wet or dry cutting without having to worry about the security issues.

The diamond segments used on laser welded diamond blades have a transition layer. This layer has no diamonds and is normally 1.5 – 2 mm thick. Its function is to connect the working layer (containing diamonds) of the segment to the steel core.

Like sintered diamond blades, silver brazed and laser welded diamond blades can also be used to cut many building materials, such as granite, marble, concrete, asphalt and ceramics. Because these blades’ diamond segments are welded onto the steel cores, these blades have to be produced piece by piece, so their production output is lower than sintered diamond blades’. However, because the steel cores do not participate in the sintering, the steel cores can be quenched and processed with other heat treatments, so their hardness and toughness can be high, therefore the diamond blades can be used in high-load and high-intensity cutting processes without deformation and high cutting efficiency can be gained.

Also because silver brazed and laser welded diamond blades’ steel cores can be treated separately, the blades’ diameter can be large, which can reach several meters. Also, the steel cores can have many designs to meet various requirements. For example, the steel core can be designed as a sandwich type which has two layers of steel cores outside and one layer of damping material in the middle. This design can reduce the noise generated in the cutting significantly, and this blade is a kind of silent diamond blade.

The bond strength of the bronze bond is high, and this can help to make better use of diamonds. Its wear resistance is good, it can withstand a larger load, and its thermal conductivity is also good. Bronze-bonded diamond tools are mainly used to process non-metallic brittle materials, such as ceramics, glass, stone, concrete as well as gemstone and semi-conductor materials. They are suitable for coarse grinding, half-fine grinding and profile grinding, and are suitable for cutting and edge grinding.

Bronze bonds also have some shortcomings. Its self-sharpening capability is not good. Bronze-bonded diamond tools’ grinding efficiency is lower than the resin-bonded ones’. If they are not properly used, block and heat may be caused, and their dressing is difficult.

The bronze bond has high strength and hardness. Its shrinkage is small and it is easy to generate dispersed shrinking holes. In addition, the thermal conductivity of Cu is only lower than the expensive Ag and is higher than other metals. This helps to decrease the temperature generated in the diamond tools’ working process and avoid burns on the workpiece.

The often adopted metal materials in the bronze bond are the powders of Cu, Sn, Zn and Ag. Sometimes some non-metal materials, such as graphite, are also added. As the objects to be processed and their processing requirements vary, the composition of the bronze bond may also be different. According to the number of metal elements in it, bronze bonds can be categorized into binary-alloy series, ternary-alloy series and multi-alloy series.

1) Binary-Alloy Series: In this series, the Cu-Sn alloy is the most common used. Some graphite is also added into the bonds of this kind.

2) Ternary-Alloy Series: This series is composed by adding a third metal element into the binary-alloy series bonds. The third metal element can be Ag, Ni, Zn, Fe, Pb, etc.

3) Multi-Alloy Series: This series bonds base on the Cu element, and have 3 or more other metal elements, such as Sn, Zn, Pb, Ag, Ni, Co, Fe, Cd, Mo, etc.

1) The pressure in hot press method is low, so the requirement to the press machine is also low, and graphite or cast-iron molds can be used instead of the ones made of high-strength alloy steel.

2) The bonding strength is high, so this method can be applied to produce complex-shape products and the reject rate can be lowered.

3) The products can be sintered with molds, so their expansion and contraction can be controlled and their sizes can be kept well. After stripping, there will be no elastic aftereffect on the pressed blanks.

4) The heating time is short and the production period is also short. This is convenient for small batch production.

5) The low pressure of this method reduces the possibility of diamonds’ crush.

6) The blank materials are sealed in molds, and will not contact with air. The heating time is short. Protective gas may not be used. These simplify the sintering process.

7) The sintering process can be better controlled.

The hot press method also has some disadvantages:

1) There are many production links in this method, and its production efficiency is not high.

2) This method needs many graphite molds, and needs many times of mold loading and stripping.

3) The graphite molds are apt to be damaged, for example, be burned to be defective or be cracked by expansion.

1) The forming of the tools does not need heating equipment, and the operation is easy.

2) The mold need not to be heat-resistant, and has a longer service life.

3) The forming production efficiency is high. The tools can be sintered in bulk.

4) The density of the formed blanks is lower than the one got via the hot press method, and their porosity is higher. This can help the cooling when these tools are used in grinding or cutting.

5) The formed waste products can be recycled timely.

The cold press method also has some disadvantages:

1) After sintering, the size of the pressed blanks changes considerably, especially for those complex-shape tools.

2) The bonding strength between the pressed blank and the tool’s body is low, and issues may arise from these bonding positions.

3) The pressure in the cold press is high. This may lead to the crush of the diamonds, and then influence the performance of the tools. There is a raw blanks’ movement procedure in the cold press method, and the raw blanks may be bumped and broken.

4) The requirement to the forming performance of the raw materials is high. The molds need to be made of high-strength alloy steel.

5) The requirement to the workers’ blank-pressing skills is rather high.

1) Cold-Press Mode: This mode is to first press the working layer (containing diamonds) and the transition layer (not containing diamonds) of the diamond segments to their forms directly on the grinding wheel’s body, and let the segments connect with the wheel’s body via teeth, slots or other manners. Then, put the grinding wheels into sintering furnaces to sinter without press.

2) Semi-Hot-Press Mode: This mode is an improved version of the cold-press mode. When the diamond grinding wheels are being sintered in the furnace, appropriate molds will be applied and some pressure will be added, but the pressure is much lower than the one in the hot-press mode.

3) Hot-Press Mode: This mode is to directly sinter the diamond segments in molds under a certain pressure in the dedicated sintering press machine, and then fix or connect the diamond segments onto the grinding wheel’s body via high-frequency welding, laser welding or mechanical mosaic method.

1) Diamond grinding is efficient, and the grinding force of it is small. The grinding temperature generated during it is lower. This can avoid burns and cracks on the surface of the workpiece.

2) Diamond grinding’s quality is good, and its precision is high.

3) The diamond grinding tools’ consumption is low, and the tools have a longer service life. This can reduce the processing costs.

4) The processing conditions of equipment, tools and workpieces can be improved, and the energy consumption can be reduced. Also, the working conditions of the operators can be improved.

5) Diamond tools not only can process materials which common tools can not process, but also create conditions for developing new materials and new equipment.