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A Buyer’s Guide to Diamond Blades

Introduction

Diamond blades are commonly used throughout construction and related industries. They are widely available in a huge array of designs and differing qualities, which makes it very difficult for the layman to know whether he is buying the right and most economical blade for his application. In producing this guide, we hope to be able to assist you in learning about diamond blades and how they work and in doing so help you to make a more informed purchasing decision.

Health & Safety

Diamond blades should be manufactured to EN 13236 which is the European standard for super abrasives. Well known testing institutes are OSA (Organization for Safety in Abrasives) and MPA-Hanover Testing Institute.

Membership of OSA requires that products meet or surpass the CEN standards for safety requirements in abrasives and that stipulated testing procedures and conditions ensure that these standards are maintained. Only the fulfilment of these requirements gives members the right to mark their products with the OSA label.

healthsafety A Buyer’s Guide to Diamond Blades

In this section:

    • The Anatomy of a Diamond Blade

The Segment
Laser Weld or Sintered
Free Backing
The Diamond
The Metal Bond
The Steel Core
The Gullet
Cooling Holes

        • Different Types of Segment

Segmented
Continuous Rim Turbo Segment
Continuous Rim

        • Variations

Turbo Segments
Undercut Protection

What is a Diamond Blade

Diamond tools represent the cleanest, safest and most efficient way of cutting, drilling, grinding or polishing construction materials ranging from extremely hard products such as baked clay, all the way through to extremely abrasive products such as asphalt.

If selected & used correctly, they will offer the user

  • longer tool life
  • faster cutting and therefore increased productivity
  • reduced exposure to HAV

The Anatomy of a Diamond Blade

A diamond blade is made up of a high alloy, heat treated steel core or blank, which is tipped with diamond impregnated, metal bonded segments. They come in a variety of grades and bonds which are designed to cut specific materials. Realistically there is no such thing as a universal blade or general purpose blade as they tend to be a compromise and we will explain the reason for this later on.

anatomy1 A Buyer’s Guide to Diamond Blades

The Segment

The various ingredients that go into the segment determine how the blade will perform and what materials it is most suitable for cutting. It is made up with a mixture of diamond grit and metal powders which form the bond that holds the diamond grit. Segments come in different depth, from 5mm up to 17mm in some cases, although changes in EN 13236 may soon make these very large segments rarer. The depth of the segment however may not be an indicator of life as a good quality 10mm segment may contain a higher concentration of diamond than a lower quality 15mm segment.

Laser Weld or Sintered

There are several ways of fixing the segment to the blade but the most common methods are sintering or by laser weld. A sintered blade is made in a similar way as a laser welded blade & complies with all necessary safety requirements, however a laser welded blade has the additional safety feature of the weld and is accepted as being the safest method of attaching segments to the blank.

Sintering is a considerably less expensive manufacturing process than laser welding and for this reason it tends to be the fixing method used on cheaper blades.

Free Backing

The bottom 1.5-2mm on a laser welded blade (known as free backing) does not contain diamonds as this would adversely affect the laser weld. Some manufacturers make blades with a larger free backing, possibly up to 3 or 4mm and this obviously reduces the production cost of the blade, whilst giving the perception that the blade will last longer. In reality the last few millimeters of free backing will not be very productive and will wear away quite quickly.

The Diamond

The diamond can be natural or synthetic, but synthetic diamonds are generally stronger and more uniform in their characteristics, resulting in a blade that will perform more consistently.

Normally a segment would contain a mixture of grit sizes and grade, determined by their shape, quality and strength. Better quality blades have a higher grade and concentration of diamond which is why they cost more.  As the blade is used the diamond grit breaks up or is pulled out of the bond. The bond then has to wear back to reveal subsequent layers of diamond.

The Metal Bond

The metal bond is a mixture of metals (known as powders) creating a bond of varying hardness which dictates how fast a segment will wear down. If you are cutting something very abrasive, such as asphalt, then the segment has to be hard or it will wear too quickly. If you are cutting something hard such as clay paviors, then the segment has to be soft or it will not wear down and reveal subsequent layers of diamond and will eventually stop cutting (this is known as polishing or glazing and is explained more in the fault diagnosis).

The Steel Core

In good quality blades, the tensioned steel core is made of high alloy, heat treated laminated steel. They may contain various features such as cooling holes which may be required when cutting very hard materials.

In cheaper blades the steel core may be made of sheet metal and may be susceptible to tension loss.

The Gullet

The gullets are to improve air flow which in turn dissipates heat and also to remove slurry from the cut. Slurry in the cut has a wearing effect on the blade, therefore the faster the slurry is removed the longer the blade will last. There are different shaped gullets; blades for asphalt tend to have wider, U shaped gullets and concrete blades tend to have narrower U shaped gullets. There are also keyhole gullets, teardrop shaped gullets and angled gullets (which theoretically remove slurry faster). Some blades have elaborately shaped gullets which are basically there to give the user the perception that the blade is high quality but in reality they may not have any great influence on performance and life.

gullets 300x123 A Buyer’s Guide to Diamond Blades

Cooling Holes

Cooling holes in the steel core may be required for blades used to cut very hard materials such as porcelain tiles or very hard concrete. They are also used on continuous rim blades because they do not have the air cooling effect of gullets and can therefore be prone to overheating which may lead to tension loss in the steel core.


Different Types of Segment

Segmented

This is the most common type and has individual segments separated by gullets of various shapes and sizes as explained above.

Continuous Rim Turbo Segment

These blades tend to have less surface area in contact with the material allowing them to cut slightly more quickly. Generally continuous turbo rim blades are used for harder materials but there are some available that are designated general purpose. As they have no gullets they sometimes tend to get hot (particularly when cutting hard materials) and therefore require cooling holes in the blank. This type of blade does not have a laser weld.

segment1 300x167 A Buyer’s Guide to Diamond Blades

Continuous Rim

A smooth, continuous rim blade is generally for use in hard materials where minimal chipping is desirable, such as porcelain tiles.

segment2 A Buyer’s Guide to Diamond Blades

Variations

Turbo Segments

Many modern segmented blades come with turbo segments which theoretically give the blade longer life as they increase the speed in which slurry is removed from the cut. Turbo segments also have less surface area in contact with the material to be cut and this allows them to cut more quickly.

Another variation on this, as in the blade below, is alternating turbo and standard flat segments. The turbo segment accelerates the rate at which the slurry is removed whilst the flat segment gives good life.

segment3 300x182 A Buyer’s Guide to Diamond Blades

Undercut Protection

When cutting very abrasive materials there is a danger that the steel core will wear away underneath the segment, which can result in segment loss. There are various forms of undercut protection to prevent this happening, such as kicker segments and wedge or hammer segments as shown below.

segment4 300x219 A Buyer’s Guide to Diamond Blades

How to Select a Diamond Blade

        1. Identify the material that is to be cut; most blade manufacturers will have a chart which shows which of their blades are suitable for which material. If you are only cutting one type of material then select the blade that is designed for that particular material as it will cut more efficiently and should offer more life. This is particularly important if you are cutting either very abrasive or very hard materials as a compromise will result in disappointment.

 

        1. If it is to be used in more than one material, i.e. concrete and asphalt, then select the material that will be cut most frequently and buy a blade suitable for that material. Any diamond blade will work more efficiently in the material it is designed for. Beware of blades that claim to cut an array of products from steel to asphalt as you will be compromising either on cutting speed, life or both.

 

        1. Once the correct type of blade has been selected, decide which quality or price bracket is required. Please remember that you cannot always determine the quality of a blade by the price as many merchants and resellers build in heavy profit margins.

 

a) More expensive or better quality blades should cut faster and offer more life and as a result offer savings over cheaper blades
b) Cheaper blades will not cut as smoothly or efficiently and will not offer as much life

 

        1. Always use a reputable supplier who is able to advise you as to which blade is most suitable for your requirements.

Commonly Used Terms & Features & What They Really Mean

        • Many blades will have Deep Segments (sometimes up to 17mm). Deeper segments are often used to convince the user that the blade will give good life but often the diamond in the segment is of a lower concentration and lower grade than a standard segment and it will not offer any greater life. Changes in EN13236 should mean that fewer of these deeper segmented blades will be available.

 

        • Turbo Segments are used because they can extend the life of a blade by removing slurry more quickly and in some instances they cut more quickly because there is actually less surface area to the segment. In recent years this type of segment has been used more often as many users perceive a blade of this type to be better quality, it is not always the case.

 

        • Cooling Holes are really only needed when cutting hard materials or if you have a continuous rim blade as they help to keep the blade cool and prevent the steel core from losing tension. Again cooling holes are often used to give diamond blades the appearance of being better quality than they actually are.

 

        • Multi Purpose Blades claim to be able to cut any construction material including steel. In reality they probably have quite soft segments which allow them to cut harder materials and deeper segments to disguise the fast wear rate. Generally speaking a blade of this type will not offer very good life in more abrasive materials such as concrete paviors or natural stone.

 

        • General Purpose Blades these days tend to be at the cheaper end of the scale. Normally a general purpose blade would have a segment of medium hardness which means that it is OK to cut a range of building materials but it would not be very good for hard materials or abrasive materials.

 

        • Sintering or sintered blades do not have the extra security of the laser weld and it is a cheaper manufacturing process. Although this type of blade complies with all regulations it is generally thought of as being not as secure as laser welded blades and it would normally be used on cheaper blades.

Fault Diagnosis

Undercutting is the premature wear of the steel blank or core beneath the diamond segment.

        • Normally occurs when cutting highly abrasive materials such as asphalt, 7N concrete blocks or green concrete
        • Persistent use in this scenario can result in segment loss
        • Correct blade selection should prevent problem from occurring

Glazing or polishing

        • As a diamond blade cuts the exposed diamond grit begins to break up or is torn out of the segment
        • The matrix or bond should also begin to wear in order to expose the subsequent set of diamonds to continue with cutting
        • If the matrix does not wear back then there will reach a point where there is no exposed diamond and the blade will slow down and eventually stop cutting
        • The tip of the blade will now feel smooth and this is known as glazing or polishing
        • Continued use in this state will cause the blade to overheat and the segment may “mushroom” over

Possible causes of glazing

        • Bond is too hard for the material it is cutting, select the correct blade
        • The machine is not powerful enough for the specification (problem found more with professional blades and floor saws)
        • The blade has been mounted with the rotation arrow the wrong way

Segment loss can be caused by the following.

        • Blade has been twisted in the cut which has caused the blade to jam
        • Steel blank has undercut, eroding the laser weld
        • The segment is too hard for the material it is cutting creating a hammering action
        • The blade has been dropped damaging the weld
        • Inadequate water supply has created excessive heat

Overheating, typically happens when cutting harder materials.

        • The blade is too hard for the material being cut and is no longer actually cutting
        • Excessive pressure may be being placed on the machine to force it through the material
        • The blade may be cutting too deep in a single pass
        • Insufficient water is being used
        • The blade will have a “bluing” discolouration on the segment or blank
        • The edge of the segment will feel smooth as no diamond is exposed, this is known as polishing
        • Continued use may cause the segment to melt and will create a mushrooming effect on the trailing edge of the segment
        • Overheating can lead to cracks in the segment or blank, loss of tension or segment loss

Cracks in the segment or steel blank

        • Cracks or breaks in the segment  can be caused by the following
        • Blade segment may be too hard for the material being cut
        • Blade may have polished and is hammering in the cut
        • Blade may have been dropped
        • Select the correct blade for the material being cut

Short blade life

        • Short blade life is generally caused by using a bond which is too soft for the material being cut. This can be rectified by selecting the correct blade for the application
        • It typically happens when cutting more abrasive materials such as asphalt, low strength concrete blocks or sandstone
        • The use of water to wash away abrasive slurry can extend life of the blade

Loss of tension in the steel blank or core

        • If the steel blank loses tension it will appear to wobble as the machine spins the blade
        • The blade may appear to be flat when removed from the machine
        • The blade will jam in the cut if used in this state

This can be caused by;

        • Overheating of the steel blank
        • Blade is too hard for the material being cut
        • Blade is spinning on spindle as it is not properly secured
        • Flanges are not of equal diameter
        • Blade is not being used at the correct speed

If all the above have been checked and the blade still doesn’t run true, then it must not be used further

Blade cutting out of round

        • Segments have worn more on one side than the other

Possible causes

        • Machine spindle and bearings may be worn causing the blade to run eccentrically
        • Machine shaft may be worn, bent or grooved
        • Blade may not be mounted correctly

Please do not hesitate to contact Pulvex should you require any further advice on selecting diamond blades or wish to discuss any of the points raised above.

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