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Selection Guide

Selection Guide - Application Help


  • 1.  Diamond Blade Selection
  • 1.1 Construction and Contractors
  • 1.2 Tiling
  • 1.3 Mortar and Crack Repairs
  • 1.4 Rescue blades.
  • 2. Cutting Discs and Wheels Selection
  • 2.1 Angle Grinder Discs
  • 2.2 Bench Chop Saw Wheels
  • 2.3 Hand-Held Petrol Saws

1. Diamond Blade Selection:
1.1 Construction and Contractors.
General: Diamond blades work by abrasive, rather than cutting action. Harder materials therefore require the application of the right grade of diamond to abrade the surface. Softer materials can be ‘cut’ using relatively few low grade diamond clusters. This accounts for most of the huge variation in price between different diamond blades of the same size.

Soft Materials: Many building materials are relatively soft. Concrete products such as paving slabs and kerbing can usually be cut with a low cost General Purpose diamond blade. Some materials such as most grades of sandstone are not only soft (except Indian ‘Sandstone’ which can be can be very hard), but are also highly abrasive with large grain structures. These will attack the metal on even the most expensive diamond blades, reducing their useful life. Hence it is sensible not to over-specify the blade as you could waste the expensive diamond you have paid for as the metal around them is eroded away. Good options for  sandstone there are the lower priced General Purpose diamond blades, or the double protected Road Slitta blades which are designed to protect against abrasive wear.

Hard Materials: Sometimes hard materials are catered for by using soft-bond metal diamond segments. This is designed so that the metal wears quickly to constantly expose fresh diamond, which may be of low grade or in low quantity.  Whilst the supplier could claim it will cut hard stone, it may not represent good value with a disappointing life span. For a good life-span, the diamond blade should have a good grade of diamond cluster that will not easily break down. These can then be bonded into a harder metal segment that will resist abrasive wear. Multi-Slysa Premium Plus diamond blades are a good example.
Some building materials are extremely hard. Long-fired clay products such as fire brick, engineering brick and some paying blocks are examples. These usually require premium diamond blades to cut them effectively.
For wide ranging use, including hard stone such as granite and Indian stone, as well as hard brick and blocks investment in a premium multi-purpose diamond blade could well be worthwhile for the time saving, Multi-slysa Premium Plus is aimed at this requirement and also includes the ability to cut ductile metal such as RSJs or scaffolding poles.

General Use: Diamond blades are available with a wide ranging cutting ability at prices which are very affordable. General Purpose diamond blades may be ‘entry’ level, but are ideal for the materials many builders and contractors use. It can be worth avoiding the cheaper ‘DIY’ grade products as these can be time consuming and will quickly glaze up on any medium to harder materials, (we do not sell DIY grade).  If you are involved in stone or cut a lot of brick, which can vary in hardness, a blade with wide cutting ability such as Multi-Slysa is ideal. This has laser welded construction for durability as well as turbo style segments, together with a good diamond content, it gives fast cutting performance in most building materials.
Asphalt and Ground Concrete: Asphalt has a very abrasive characteristic. Diamond blades for floor saws usually have some protection against premature abrasive wear of the metal. This is most important where the diamond segments are bonded to the metal disc. An effect known as undercutting can occur where the disc is eroded on the weld and a segment is lost long before its useful life has been used. An asphalt diamond blade therefore usually has one of two methods of protection. 
  a. 2-3 ‘dropped’ segments which are welded lower into the metal disc resulting in the debris being cleared from the path of the welds of the following segments. Alternatively 2-3 skewed segments which expel the abrasive waste are employed.
  b. Tungsten carbide inserts can be employed on the leading edge of the welds. This protects the most vulnerable are of the diamond blade.
Road Slitta diamond blades employ both skewed segments and tungsten carbide inserts to  give optimum life.
Ground concrete, often known as green concrete before it is cured, is also highly abrasive, especially in its ‘green’ state. This makes a protected blade ideal for ground saws in this application also. Cured concrete on the other hand, can be quite hard, depending on the aggregates. To cater for these various needs some suppliers offer up to 3 different types of ground saw diamond blades. This can be a nuisance when a variety of surfaces are to be cut for a single task. Consider for instance the installation of a utility from the road main to a factory. The trench will typically need to be cut through the road asphalt, across a pavement, through a car park and into a concrete floor. How many blade changes should the contractor make? A better option is the use of a protected blade for the abrasive materials with a good diamond concentration for the harder concrete aggregates, ie one blade to do the whole job. We offer such a diamond blade in Road Slitta, which is highly popular with contractors for use on both floor saws and hand held petrol saws.

1.2 Tiling:
Tile cutting with diamond blades can now be undertaken by two types of method: 
- A fixed cutting machine ranging from small DIY tile saws taking diamond disc blades, usually from 110mm upwards, to industrial moving table saws for larger slabs. These are usually wet cutters.
- A hand held angle grinder. These require diamond blades capable of being used dry.
The wide range of tile materials requires different cutting solutions. A standard tile disc blade is suitable for most ceramic tiles. Whilst these have a hard face, the coating is usually thin, with a softer backing material, which makes for relatively easy cutting. The continuous rim of  a standard tile blade gives a low-chip cut and would normally require water cooling. Smaller diameters, eg 115mm may be suitable for dry use on an angle grinder, but larger sizes may distort and have diminished lives due to heat if used dry.
Porcelain and glass tiles are usually solid all the way through and can be much more difficult to cut. The standard cutting discs supplied with most machines are not usually suitable for these materials and users may find progress disappointingly slow, whilst the temptation to apply pressure may result in excessive chipping. The best blades for these applications have narrow section so that the abrasive action is more concentrated on a smaller area. They also require a high grade of diamond cluster, which is why these diamond blades are much more expensive .  Premium ranges for porcelain and glass include Tile Slysa Premium, a smooth cutting thin blade, and Tile Slysa Turbo Premium, with a ‘turbo’ edged thin blade. This latter design is better for angle grinders as it cools better for dry use. It also has a stiffening flange to minimise risk of flexing, which can be a problem on some tile cutting machines with tilting tables.
Sometime tillers find it easier to clamp the tile and cut it with an angle grinder. This requires a diamond blade suitable for dry cutting. In practice most tile blades of 115mm (standard small angle grinder) will perform OK when dry. Turbo-edged blades are better at self cooling and the Tile Slysa Turbo Premium is ideal for use on angle grinders to cut hard porcelain.

1.3 Mortar and Crack Repairs

Mortar raking diamond blades, or mortar rakes, can save a lot of time compared to mechanical chisels or picks, especially on straight runs between rows of brick. They also reduce potential impact damage, resulting in fewer cracked bricks and they won't add to the crack damage in mortar as an impact method might. Used on an angle grinder, they are wide diamond blades, usually around 6.4mm (1/4") or 8.5mm thick. The aim is to neatly remove old, crumbing or damaged mortar in order to be able to re-point the joint to seal the brick or stonework.

Mortars vary enormously in hardness. Old lime mortars may be quite soft, whilst modern mortar mixes tend to be of a medium hardness. Occasionally, extremely hard mixes have been used. Often, a wall with years of service and a history of repairs carried out by different people will have a variety of types. Good mortar raking diamond blades will therefore cope with both hard and soft mortar types. Similarly, there can be huge variation in the abrasiveness of the mortar. This largely depends upon the sand or grit used in the mix. The issue with abrasiveness as far as diamond blades are concerned, is that an abrasive mortar risks wearing down the metal around the diamonds, before good use can be made of the diamonds. It is thus highly desirable that manufacturers do not use a soft-bond in order to compensate for a low diamond content.

We offer 2 styles of mortar raking diamond blades. The most economical is a simple, but clever concept of 2 diamond blades, co-joined on a central flange, known as a dual-cut mortar rake. Because the cost of the middle section of the blade is obviated, these blades cost much less than traditional designs. By using blades with segments designed for hard materials and because they are doing as much cutting as grinding, they are ideal for a wide range of mortar types.

 Dual cut mortar raking diamond bladePremium mortar rakeMortar raking finger

For durability, many professionals prefer premium mortar raking blades. These have premium grade diamond segments which are laser welded. They also have tungsten carbide inserts set into the leading edges of the welds to resist undercutting from the abrasive action of mortar dust. This gives a fast working blade, giving a highly consistent cutting width and great durability. This range extends right up to 230mm enabling you to get maximum depth from a 9in angle grinder. This can be very useful for inserting lead flashing or other roofing and water-proofing materials. 

For random stonework and the short runs on brick, a mortar raking finger is often more convenient. These tools fit directly to the M14 spindle of standard angle grinders. They are coated in tungsten carbide grain to given their abrasive action. They may require a masonry bit to make a start hole, from which they can be guided around the stone or brick-work with the angle grinder. 

Concrete cracks can be difficult to repair if they are not prepared properly. A crack chaser, or crack chasing diamond blade, is designed to open out a crack, so that the edges are clean and there is adequate space to pour in the repair mix. These blades are used on angle grinders. They have axe-head profile segments, so that they cut-in well, even into the hardest mixes. These chunky segments give these discs a lot of inertia. We therefore offer a max diameter of 180mm, this being a sensible limit for a 230mm angle grinder to accelerate without causing undue stress to the electric motor.

1.4 Rescue Diamond Blades

Rescue blades were once just supplied to rescue services and their purpose was to be able to cut through just about anything they encountered. For example, in an earthquake situation, they would cut the tangle or random concrete, brick, stone, metal and wood, without changing the blade. These days, this same versatility can be applied to a much wider market as prices have dropped to be affordable by most trades. They are now very useful for re-cycling, demolition, refurbishment and cutting mixed materials and composites in fabrication.

Rescue blades work by diamond being bonded onto the outside of the carrying segments, rather than within them. This means that you get a direct diamond to material contact and a rapid cut rate. The diamond is bonded by a process called vacuum brazing. This provides an extremely robust bond and the blade is this suitable for a wide range of materials. It is particularly useful for applications where there is no other obvious solution. For example, nails in wood would tend to damage a tungsten carbide tipped circular saw blade, but a rescue blade would quickly slice through them as well as the wood. The cut is not particularly clean, but for the vast majority of their potential applications, this really does not matter. 

2. Cutting Discs & Wheels Selection

2.1 Angle Grinder Discs.

Angle grinders are high speed machines with a typical 115mm machine reaching 12,000rpm no-load speed, equating to nearly 80m/s. Safety is thus paramount when using bonded abrasive discs, which if used incorrectly can break up causing pieces to fly off at dangerous speeds. Safety training is addressed elsewhere, but suffice to say here that correct safety gear and correct usage should be paramount when choosing and using bonded abrasive discs and wheels.  

Standard EN12413 is a useful start to safety and it is worth seeking compliant products, although this standard is not mandatory for either sellers or users. The European standard does include some requirements such as date stamping which is considered un-necessary in other countries such as USA. This originates from the time when bonded abrasive products would use natural resins, which could deteriorate over time. These days synthetic resins are almost universally used and these are far more stable. The date code, in quarters, still gives a useful guide for stock rotation, but what is far more important is correct storage. At Right Lines bonded abrasive discs are stored in a humidity controlled environment to minimise the risk of deterioration in storage.

Cutting discs for angle grinders are available in 2 main categories characterised by thickness. Standard metal cutting discs are approx 3.2mm (1/8in) thick and give a good life on mild steel and cast iron, especially on any thicker section. Thin cutting discs, also known as slitting discs, are approx 1.2mm thick and were initially designed to cut stainless steel sheet. The thin section means that the abrasive action is concentrated on a smaller area, resulting in faster slitting of hard metal. The Right Lines thin cutting discs are made from materials which are assured free from potential contaminants to stainless steel. They can thus be used on stainless without the concern of causing corrosive contamination. More recently, thin discs have become popular for use on all metals, even if this can mean shorter life when cutting thicker steel section. We have now responded to this trend by introducing a Premium cutting disc which gives longer life on all steels, whilst still being 1.2mm thick for fast cutting. Despite an observable fad in the market, we choose not to reduce the thickness below 1.2mm as we believe it high desirable for a cutting disc to retain its rigidity in order to hep cut in straight lines. We see little merit in saving 0.2mm for example on the disc width, if the cut then goes adrift by 2-3mm due to flexing.

2.2 Bench Chop Saw Wheels.

A popular fixed metal cutting saw is the bench mounted chop saw, most popularly in 14in size. We stock both standard and stainless steel grade wheels for these saws, the standard grade being 3.2mm thick and the stainless grade just 2.8mm thick. The metal should always be clamped when using these saws to avoid work-pieces flying off and to help prevent the cutting wheel from jamming.

2.3 Hand-Held Petrol Saws.

Latest generations of hand held petrol saws tend to have higher speeds than their predecessors, meaning that peripheral speeds are now higher than the 80m/s rating of standard cutting wheels. We therefore supply higher speed rated wheels, made with extra reinforcing, for these saws. These are 100m/s speed rated and are denoted as such under EN12413 by a green stripe.