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How to Cut Concrete

Hanjiang Wang — Sat, 30 Jul 2011 08:58:24 +0000

Concrete is usually cut with diamond blades. There are different solutions to perform concrete cutting under different circumstances.

If the job is of shallow cutting and small scale

In this case, you can use a 4″ or 5″ angle grinder, and a 4″ or 5″ sintered diamond blade, for example, segmented diamond blade, turbo diamond blade, or turbo wave diamond blade, mounted on the grinder. Segmented diamond blades may cause more chips during the cutting due to their segmented rim, but they are cheaper. Turbo wave diamond blades can be used to perform higher load tasks for their strengthened steel core, but their price is the highest in these 3 kinds of sintered diamond blades.

You can first cut the concrete to 1/4″ deep, and see how the angle grinder and the diamond blade respond. If no problem, you can do further passes of cuttings to reach the depth of the cut you need. Each cutting pass should not be deeper than 1/2″.

To reduce the dust, you can ask someone to spray some water onto the diamond blade and the cut during the cutting process. This can also help to cool the diamond blade and extend its life. If it is not safe to use water for the electric power source of your angle grinder, you should cut the concrete dry. As dry cutting uses the air as the coolant, after a period of cutting you should release the pressure on the diamond blade and allow it to rotate freely to let the air cool it. The period can be a few minutes to a few seconds depending on the hardness of the concrete being cut (the harder the concrete, the shorter the cutting period should be).

Throughout the cutting process, you should wear a professional respirator, for the dust can seriously hurt your health.

In addition to angle grinder, you can use a circular saw to do the job. Circular saws have a baseplate which can help to keep the cut straight and uniform. With a circular saw, you can also use a bigger diamond blade, e.g., 7″, to improve the cutting efficiency, for circular saws are stabler.

If the job is of deep cutting or big scale

If your cutting is deeper than 4″ (about 100mm) or the job scale is fairly big, you should use a wet concrete saw and laser welded diamond concrete saw blades to do the job. The concrete saw can be a handheld cut-off saw, a walk behind saw, or another type. The diameter of the laser welded diamond blade is usually no smaller than 12″ (300mm). The concrete saw and the diamond blades can be either bought or rented. To obtain good cutting result and improve cutting efficiency, you can follow below steps to prepare the concrete cutting:

1. Identify what concrete you will cut

There are many types of concrete, and they should be cut with different types of diamond blades.

Some concrete has steel bars (reinforced concrete). If your cutting depth is about 4″ or deeper, you may meet the steel bars halfway. There are diamond blades specially for cutting reinforced concrete.

The curing time of concrete varies. Fresh (green) concrete is more abrasive, and old (cured) concrete is harder. Diamond blades for cutting green concrete and cured concrete are also designed to be different.

If possible, you can further investigate the aggregate and the sand of the concrete, for these information can help you to choose the more suitable diamond blades. Hard aggregate like basalt and quartz dulls the diamonds on the blade faster, so the blade’s bond should be softer to let new diamonds be exposed more easily. The size of the aggregate also affects how hard the blade’s bond should be. Small aggregate (smaller than 3/8″) wears the blade faster than big aggregate (bigger than 3/4″). The type of the sand affects the concrete’s abrasiveness. Sharp sand such as crushed sand and river bank sand is more abrasive than round sand like river sand.

2. Choose the proper diamond blades

Though silver brazed diamond blades were used widely in wet concrete cutting before, now laser welded diamond blades are more common for their firm laser weld and high performance.

You should check what diameters of diamond blades your concrete saw can accommodate, and the saw’s arbor size which the arbor hole on the diamond blade should match. Also, you should examine the horsepower of the concrete saw. The saw’s horsepower affects the diamond blade selecting. Diamond blades used on big horsepower saws should have harder bond or higher diamond concentration, otherwise the blade may be consumed very quickly.

Then, you can tell the diamond blade’s diameter and arbor hole size, the horsepower of your concrete saw, along with all the detailed information of the concrete you get in the first step to your diamond blade supplier. The supplier should know which kind of diamond blade may fit your job.

3. Determine wet cutting or dry cutting

Concrete is usually cut with water (wet cutting), for cutting concrete with adequate water can significantly reduce the dust, keep the diamond blade cool and extend its life, and improve the cutting efficiency (for wet cutting can be deep and continuous).

However, when there is no water source near the work area, you have to perform dry cutting. As said in the previous section, dry cutting should be intermittent and shallow. If deep cutting is needed, you should do several passes of shallow cuttings.

4. Wear enough personal protective equipment

You should at least wear a professional respirator, not only in dry cutting, but also in wet cutting, because the small dust particles generated in the concrete cutting process can penetrate deep into the lungs and can cause serious health effects such as lung cancer or silicosis. If the job is big, other equipment like goggle, earplugs, and protective clothing should also be adopted.

5. Pre-cut a shallow straight line on the concrete

To make the cut straight, you can use a chalk line to mark a straight line on the concrete, and then place a straight wood board along the line. Then you can cut a shallow line on the concrete along the wood board. The cut can be about 1/4″ deep.

Having this shallow straight cut, you can perform further cuttings along it to gain the cut you need.

More tips for concrete cutting

Concrete can also be cut with abrasive blades, but diamond blades are recommended, for diamond blades can provide at least two times faster cutting, less downtime, and constant depth of cuts.
If you use the diamond blades occasionally and your jobs are small, you can choose the economical grade diamond blades to save your expense (but the cutting speed of the economical diamond blades should be fast enough). If you use the diamond blades frequently or the job is big, you should choose high grade professional diamond blades, for this can decrease your cost per cut.
If you are not sure that you can do the concrete cutting job well, you can just hire a professional concrete cutting company to do the job for you.

8 Easy Tips for Buying the Right Diamond Blades You Need

Hanjiang Wang — Thu, 30 Jun 2011 03:51:14 +0000

Do you know high quality diamond blades may not work well for your job? This is true. Your diamond blades should fit your application. Here we give 8 easy tips you can use when you are buying diamond saw blades.

1. What material you want to cut

Diamond blades can be manufactured to be very different for cutting different types of materials. So tell your supplier the material you want to cut, e.g., reinforced concrete, concrete road, asphalt, granite, marble, bricks, or ceramic tiles. The more detailed is the information about the material, the better. For examples, you can tell your supplier the diameter of the steel bars in the reinforced concrete, the aggregate of the concrete, whether it is a green concrete or cured concrete, how hard your marble is, and so on.

2. Wet cutting or dry cutting

If you use a wet diamond blade in dry cutting, it may take just a few seconds for the blade to be damaged, and even worse, this may cause serious security issues. Wet diamond blades and dry diamond blades are designed to be different. So always tell your supplier this information. Concrete saw blades are usually designed for wet cutting.

3. Professional use or DIY use

Professional diamond blades are usually for frequent uses, so cost per unit of cutting length is more important than the blades’ unit price. High quality long-life diamond blades are more cost-effective for professional use though their unit prices are higher.

DIY diamond blades, however, are often for small jobs and occasional use. Their lifespan need not be very long, so cheaper diamond blades with shorter lifespan are an economical choice for DIY jobs. But the cutting speed of DIY diamond blades should be acceptable.

Therefore, letting your supplier know whether the blades are for professional use or DIY use can save your expenses.

4. The horsepower of the saw machine on which the diamond blades will be used

Diamond blades used on big horsepower saw and small horsepower saw are also designed to be different. During the cutting process, big horsepower saw exerts bigger torque on the diamond blade and the blade’s segments receive bigger impact. In this case, the segments’ diamond concentration should be higher to decrease the impact on single diamonds or their bond should be harder to hold the diamonds more firmly. If you use a diamond blade that fits small horsepower saws on a big horsepower saw, the diamond blade may be consumed very quickly. On the contrary, if you use a big horsepower saw blade on a small horsepower saw, the blade may cut slowly or even does not cut because of its high diamond concentration or hard bond. So tell your supplier the horsepower of your saw, and he should know what diamond blades may fit your needs.

5. Make sure the diameter of the diamond blades and their arbor hole size

The diameter of the diamond blades and their arbor hole size should match your saw machine.

6. The segment height

Diamond blades with higher segments will have a longer lifespan. However, the segments cannot be too high. Because during the cutting, higher segments will make the joints (e.g., welds) that connect the segments to the blade’s steel core bear bigger torque. If the joints or welds fail to withstand the torque, one or more segments may break off the blade and may fly out, and may hurt the people nearby. The common segment height of 14″ diamond blades is 10mm or 12mm.

7. The segment thickness

Normally, you do not need to tell your supplier the thickness of the segments. There are default segment thicknesses for different diameters of diamond blades. But if you want to further improve the cutting speed of the diamond blades, you can ask your supplier to make the segments thinner. This often needs the steel core to be made thinner also.

8. Find a good supplier

Finding an honest and reliable supplier is very important. A good supplier can suggest which type of diamond blade can fit your application, and provide you with good products.

Why the Segment of Diamond Blades Can Break Off

Hanjiang Wang — Mon, 13 Jun 2011 02:52:15 +0000

A common problem diamond blade users may encounter is that one (or more) segment break off the diamond blade. This problem is often known as segment loss, which not only means the damage of the diamond blade, but may cause serious security issues because of the segment flying out.

A laser welded diamond blade with a segment lost

The reasons of segment loss (break) of diamond blades are diverse. If diamond saw blades has no problem in quality and the segments are connected to the blade’s steel core firmly, the following causes may lead to segment loss:

1. Wet diamond blades are used with inadequate water or even dry

During the cutting process, if there is no adequate water flowing on both sides of the diamond blade and in the cut, excessive heat may be generated and there may be some abrasive slurry remaining in the cut.

If the wet diamond blade is laser welded, the abrasive slurry can wear away the blade’s steel core just beneath the segment. This problem is often called undercutting. Serious undercutting can cause the segment to break from the steel core.

If the wet diamond blade is silver brazed, the excessive heat can cause the silver solder which connects the segments to the steel core to be melted, and then the segments may break off.

So adequate water is critical to the wet cutting job, for it can avoid overheating of the diamond blade and can wash out the abrasive slurry. Overheating can also make the diamonds on the segments become blunt. If a wet diamond blade is used without any water (dry), it may take just a few seconds for the blade to be damaged.

2. Dry diamond blades are not used properly

Laser welded diamond blades can be designed to cut some materials without water. However, if dry laser welded diamond blades are used dry arbitrarily, the segment may still break off the diamond blade.

As dry cutting utilizes the air as its coolant, dry diamond blades should be used in the intermittent and shallow sawing mode to allow the air to flow around the blades to dissipate the heat. You can read our how to use diamond blades in dry cutting article for more information. If a dry diamond blade is used in continuous or deep cutting, the blade may be overheated and may lose its segments.

Not all materials can be cut dry. Some very hard materials, e.g., concrete with strong reinforcement, should still be cut with water. Wet cutting can improve cutting efficiency, control dust, and extend the diamond blade’s life.

3. Problems related with the saw machine

If the saw machine’s blade shaft or shaft bearings are worn, the diamond blade may jump up and down in the cutting process. This can lead to segment loss. Replacing the shaft or shaft bearings can resolve the problem.

Some other reasons can also make the diamond blade flutter and then cause segment loss. These reasons include: the diamond blade is mounted on the shaft incorrectly; the nuts or bolts which hold the flange and blade shaft together are not wrenched tight; there is dirt, sand or other materials between the blade steel core and the flange.

4. The material being cut slips and jams the diamond blade

This situation is typically seen in masonry or tile sawing applications and may cause segment loss. To avoid this, the operator should make sure that the material is seated securely on the saw machine, and that he holds the material firmly through his entire cutting process.

How to Use Diamond Blades in Dry Cutting

Hanjiang Wang — Mon, 30 May 2011 03:24:32 +0000

Normally, using diamond saw blades with adequate water (wet cutting) can extend the blades’ life and control dust. However, in some situations, dry cutting should or has to be performed. These situations include:

For some electrical power tools, it is not safe to use water because of the electrical power source.
The work area needs to be kept dry.
Water source is not available near the work area.

1. Choose proper dry-use diamond blades

If you need to perform dry cutting, you should first choose the proper diamond blade which can be used dry. Diamond blades for dry use are normally different from the ones only for wet use. For sintered diamond blades, continuous rim diamond blades are usually only for wet cutting. Most of other sintered diamond blades can be used dry. For welded diamond blades, silver brazed diamond blades cannot be used in dry cutting, while dry-use laser welded diamond blades can. You can read our diamond saw blades introduction article for more information. Dry-use laser welded diamond blades are designed different from the laser welded diamond blades that are only for wet use.

Dry diamond blades usually can be used wet. But if a wet diamond blade is used with inadequate water or even dry, the diamond blade may be overheated and damaged, and even worse, the segment on the blade may break and fly out, and may hurt the operator or the people nearby.

So tell your diamond blade supplier that you need dry cutting, and let him/her choose proper dry diamond blades for you.

2. Operate dry diamond blades properly

After obtaining a right diamond blade for dry use, if the operator fails to operate properly, the excessive heat generated in the dry cutting process may still damage the diamond blade, and the operation can be very dangerous.

Unlike wet cutting using water as the coolant, dry cutting uses air to cool the diamond blade. During dry cutting, the operator should perform intermittent and shallow cuttings to allow the air to flow around the diamond blade.

Intermittent Cutting: The operator should not do long time continuous dry cuttings. Instead, after some time of dry cutting, he should take the pressure off the diamond blade, and let the blade run freely and to its full speed to allow the air to keep it cool. The duration of each dry cutting operation can be a few minutes to a few seconds depending on the hardness of the material being cut. The harder the material, the more often the diamond blade should be allowed to cool.
Shallow Cutting: The operator should also perform shallow cuttings to avoid the diamond blade’s overheating. When deep cut is needed, he can do several passes of shallow cuttings (step cut) to achieve it.
Do not force diamond blade into the material: The operator should allow the diamond blade to cut at its own speed. Forcing the blade may cause overheating and blade damage.

More information, if you experience problems with wobbling when performing dry cutting with a high-power handheld saw machine, try wet cutting. This can cool down the diamond blade and solve the problem. Not all materials can be cut dry. Very hard materials, for example, concrete with strong reinforcement, should still be cut with adequate cooling water. For concrete saws, wet cutting is preferable as it allows continuous and deeper cuttings, reduces the dust, and can prolong the diamond blade’s life.

3 Main Criteria for Evaluating a Diamond Saw Blade’s Performance

Hanjiang Wang — Tue, 27 Jul 2010 09:07:25 +0000

There are 3 main criteria when evaluating the performance of a diamond saw blade: cutting efficiency, service life and processing quality.

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 cuts which the diamond blade makes on the material. This criterion mainly includes the flatness and roughness of the cut surface, the parallelism of the two sides of the cut, and the integrity of the edges.

Diamond Grit’s Influence on the Performance of Diamond Saw Blades

Hanjiang Wang — Mon, 19 Jul 2010 10:15:32 +0000

Diamond grit indicates the size of the diamond. The diamond’s protrusion height on the cutting surface of the diamond saw blade influences how deep the diamond can cut, while deeper cutting means higher cutting efficiency. If the diamond is big, its exposed portion can be higher, so its cutting efficiency can also be higher. Therefore coarser diamond grit leads to higher cutting efficiency of the diamond saw blade.

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 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’s Influence on the Performance of Diamond Saw Blades

Hanjiang Wang — Sat, 17 Jul 2010 10:12:07 +0000

The meaning of a diamond tool’s diamond concentration is the weight of the diamonds in a unit volume of the diamond tool’s working layer, and it is defined that when each cubic centimeter contains 0.88g diamonds, the concentration is 100%. This definition also applies to CBN abrasives.

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.

Wholly Sintered, Silver Brazed and Laser Welded Diamond Saw Blades

Hanjiang Wang — Sat, 12 Jun 2010 10:12:03 +0000

Perhaps the most commonly sighted diamond circular saw blades are the sintered metal-bonded ones, on which diamonds are mixed and sintered with metal bond materials to form the blades’ cutting edges — diamond segments. Normally, these blades are made via 3 methods: wholly sintering, silver brazing and laser welding. The diamond blades made via these 3 methods are different and have their respective features and applications.

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. Therefore laser welded diamond blades can be used to cut some relatively softer materials (e.g., many kinds of stone) without the water cooling (dry cutting). But please note, when cutting very hard or abrasive materials, for example, concrete containing reinforcing rebar, the laser welded diamond blade should still be used with adequate water. Otherwise, the diamond segment itself may break or the steel core below the segment may wear off and break, and then cause serious security issues. Laser welded diamond concrete saw blades are usually made for wet cutting applications.

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.

Sandwich Diamond Segments of Diamond Blades

Hanjiang Wang — Tue, 08 Dec 2009 09:19:21 +0000

Earlier diamond segments of diamond circular blades were all designed to be even cuboids. Later, people found that, after a period of sawing, the two sides of the segments are easier to be worn than the middle, and the segments become a convex shape. The convex-shape diamond segments have a larger contact area with the material being cut, therefore the diamonds on them are easier to be ground blunt and then need dressing. In addition, as the sawing force will also increase, the core of the diamond blade tends to be distorted and be deformed for vibrations. This can influence the cutting precision, and reduce the blade core’s service life. Sandwich diamond segments, which have higher side layers and lower middle layers, however, can solve this problem to a great extent.

A Kind of Sandwich Diamond Blade

Sandwich diamond segments can be made via the following methods:

The diamond concentration in side layers is higher than the one in middle layers.
The bond material in side layers is more wearable than the one in middle layers.
The diamond’s grade in side layers is higher than the one in middle layers.
Make the working length of middle layers shorter than the one of side layers via structural designing.
Add non-working layers into the multi-layer structure, and adjust the width ratio of working layers and non-working layers.

Why Diamond Segments Have Different Shapes

Hanjiang Wang — Thu, 03 Dec 2009 04:08:45 +0000

The shape of diamond segments is an important factor influencing the performance of diamond saw blades. The different shapes are directly related to cutting efficiency and the ratio of the diamonds’ non-normal failure.

Currently, there are many kinds of shape diamond segments, for example, convex segments, layered sandwich concave segments, L-shape segments, step-shape segments, segmented segments and side-slotted segments.

Various Shapes of Diamond Segments

The designing for the shape and structure of diamond segments mainly has two purposes. The first is to increase the diamond blade’s capabilities of containing and discharging sawdust, and improve the cooling and lubricating conditions. The second is to reduce the friction between the segments and the material being cut as well as the sawdust, improve the blade’s cutting capability, and thus save energy and improve the blade’s performance.

As there are slots on the rim of diamond blades, the length of diamond segments also influences the blade’ performance. In sawing, the diamonds on the front of the segment, which enter the cutting arc earlier, bear more loads than the diamonds on the back of the segment. Therefore we can segment the diamond segments properly, so that the performance of the front end and the back end of a diamond segment matches the loads they bear.