Safe use of abrasive wheels - fact sheet

Information about the safe use of abrasive wheels and tools in the workplace.

SINOTOOLS Product Page

Background

Abrasive wheels are typically used within industry for grinding, shaping or cutting metallic objects. They may be fitted to either portable / hand-held (angle grinders) or fixed grinding machines (mounted to a bench or pedestal).

There are various types of abrasive wheels to suit different applications. This guidance primarily focuses on fixed grinding machines fitted with wheels formed by abrasive particles being bonded together, i.e. bonded abrasives.

The hazards

When using abrasive wheels, injury may occur from contact with the rotating wheel or wheel breakage.

Bonded abrasive wheels are inherently fragile and can be easily damaged. Abrasive wheels which contain damage or flaws have the potential to fracture and break apart during operation. This may result in serious or fatal injuries due to the high velocity of the ejected parts.

Figure 1 shows an example of a bonded abrasive wheel (300mm diameter) which broke apart during operation, resulting in fatal injuries to the operator.

Practices likely to affect the integrity of a grinding wheel include:

• incorrect application
• improper mounting
• malpractices during grinding operations
• grinding machine defects and
• poor storage and handling.

Abrasive wheel selection

Not all abrasive wheels are the same. When selecting an abrasive wheel, you must ensure it is compatible with the grinder and is suited to the intended application. The use of incompatible abrasive wheels may cause the wheel to fracture. You should consider:

• compatibility with the material and task.
  Abrasive wheels are manufactured from various abrasives, grit sizes and bonding materials to suit a range of applications. Where doubt exists contact the manufacturer to determine suitability
• compatibility with the grinding machine.
  • The maximum operating speed marked on the wheel must be greater than the spindle speed of the grinder
  • The physical characteristics of the wheel such as: outer diameter, width, bore diameter and shape (straight sided, tapered, cupped, etc)

Mounting / installation

Abrasive wheels must be installed by an appropriately trained person. When preparing to install an abrasive wheel, the wheel should be closely inspected for any signs of damage. Damaged wheels must not be used. The installer must confirm compatibility (with material, task and machine) prior to installation.

Doing a ring test

Cracks in abrasive wheels may not always be visually evident, but many wheels can be checked for cracks by carrying out a ring test. This is achieved by suspending the wheel from the bore (either on your finger or small pin) and tapping it with a light, non-metallic implement (heavy wheels should be supported on a clean, hard surface). The wheel should produce a clear metallic ring. If the wheel sounds dull or dead, it may be cracked and should not be used.

Read the manufacturer's instructions

As some variation exists between different grinding machines and abrasive wheels, the installer should refer to the machine manufacturer&#;s instructions for the relevant installation and retention requirements. Typical installation requirements include:

• the machine spindle should be free of burrs or damage (Figure 2). The wheel should fit freely but not loosely on the spindle
• the abrasive wheel should be mounted between recessed flanges of equal diameter which are usually at least one third of the diameter of the wheel. The contact faces of the flanges must be free of burrs or rough edges which may otherwise damage the wheel
• a bush (where used) should not project beyond the sides of the wheel
• the clamping nut should be tightened only sufficiently to hold the wheel firmly
• the guard and work rest should be reinstalled, and clearances adjusted. Before turning the power on, turn the wheel by a hand a few revolutions to confirm it clears both the work rest and guard

Safe work practices

Workers must receive relevant training on how to safely operate a grinder. The training must be specific to the type of grinder and the tasks being undertaken. Examples of safe work practices include:

PPE and appropriate clothing

• appropriate personal protective equipment must be used
• loose clothing may be drawn in between the wheel and workpiece and should not be worn. Similarly, long hair should be tied back
• ensure grinding is carried out in an area away from other workers and the working area around the grinding operations are kept clear

Correct operation of grinder

• new or re-fitted wheels should be trial run at full operating speed for at least one minute before the workpiece is applied. During the trial run everyone should stand clear
• excessive vibration usually indicates that the wheel is out of round. Such wheels should not be used until they have been balanced by dressing. Wheels which cannot be balanced by dressing shall be removed
• never force the wheel by exerting excessive pressure on it. The wheel characteristics (abrasive, grit size, grade and porosity) govern its cutting power
• never grind on the side of the wheel unless permitted by the wheel manufacturer. Most wheels are designed for grinding on the outer (peripheral) surface only
• ensure the work rest (where fitted) is adjusted as close to the wheel as practicable and securely fixed in position. The gap between the wheel and work rest should be maintained at less than 2mm as the wheel wears down
• never impact the wheel with tools or the workpiece. Contact with the wheel shall be made by exerting gradual, even pressure.

Guarding

A guard of adequate strength should be provided, where practicable, to achieve the following:

• contain wheel fragments in the event of fracture
• reduce the likelihood of the operator coming into contact with the wheel
• protect the wheel against inadvertent damage
• prevent an oversize wheel from being fitted.

The guard must be fabricated from a material of adequate strength to withstand the impact force of any ejected wheel fragments.

The guard should enclose the wheel to the greatest possible extent, keeping the opening as small as possible. Adjustable hoods or tongues may also be incorporated into the guard to compensate for the increased exposure as the wheel wears down.

When a guard is constructed from several component parts, the fasteners shall be of adequate strength to prevent separation of the guard in the event of wheel failure. This also applies to any fasteners used to anchor the guard to the machine frame.

Personal protective equipment

Suitable eye protection shall be provided and used by operators for all grinding operations.

Protective visors or shields may be installed on some fixed grinders to protect the operator from flying particles. However, these devices shall not exclude the use of eye protection.

Other personal protective equipment may be required depending on the nature of the grinding operation. This may include aprons, gloves, safety shoes, hair nets, hearing and respiratory protection.

Maintenance/ inspection

The grinder must be inspected prior to each use and maintained in accordance with the manufacturer&#;s requirements. Inspection and maintenance may include ensuring the:

• machine is kept clean and free of grinding dust or other contamination
• wheel is in serviceable condition, i.e. undamaged, balanced, no evidence of loading (clogged with material) and dimensionally acceptable
• work rest is undamaged, adjusted as close to the wheel as practicable and securely fixed in position
• protective guard and visor (where fitted) are secure and undamaged. Inspect guards for cracks and retention of all fasteners
• machine spindle is undamaged and there is no excessive play
• exhaust system (where fitted) is functioning correctly
• electrical safety of the machine, including switches, supply lead and Residual Current Device (RCD) where fitted.

Wheel dressing

Dressing is a process where material is removed from the working surface of the abrasive wheel. Dressing is necessary for efficient production and maintaining the integrity of the abrasive wheel. Frequent light dressings are generally preferable to occasional severe dressings.

A revolving cutter type dressing tool (Figure 3) is most commonly used for dressing. When using this type of dressing tool, it should be supported on the work rest, with the work rest adjusted away from the wheel to allow the heel of the dresser to hook over the work rest.

There are many types of abrasive wheel dressers, with different methods of use. Where necessary, the wheel and machine manufacturers should be consulted to confirm the most appropriate method.

Handling and storage

Care shall be exercised when handling and storing abrasive wheels to prevent damage. All abrasive wheels are fragile, though some are more susceptible to damage than others. Appropriate precautions include:

• handle wheels carefully to prevent dropping or bumping them together
• do not roll wheels
• use suitable plant which provides adequate support to transport large wheels.

Abrasive wheels should be stored in an area that is dry and not subject to large changes in temperature. Some bonded abrasives may be affected by excess humidity, dampness and extreme temperatures.

The wheels should be stored in suitable racks and located as near as practicable to the grinding location but remain protected from traffic or excessive vibration.

Wheels may be stored horizontally on a flat surface or suspended vertically from pegs through the centre hole of the wheel. Guidance should be obtained from the manufacturer to determine the most appropriate method of storage, especially for thin wheels.

Further information

• Australian Standard AS.1- Abrasive Wheels, Part 1: Design, construction and safeguarding
• Australian Standard AS.2- Abrasive Wheels, Part 2: Selection, care and use
• Health and Safety Executive (HSE), UK, guide: Safety in the use of abrasive wheels

Back to top

Abrasive cutting tool for grinders

This article is about the modern abrasive cutting tool. For the traditional tool, see Grindstone . For millstones as grinding wheels, see Millstone . For the Overkill album, see The Grinding Wheel

Various types of grinding wheels

Grinding wheels are wheels that contain abrasive compounds for grinding and abrasive machining operations. Such wheels are also used in grinding machines.

The wheels are generally made with composite material. This consists of coarse-particle aggregate pressed and bonded together by a cementing matrix (called the bond in grinding wheel terminology) to form a solid, circular shape. Various profiles and cross sections are available depending on the intended usage for the wheel. They may also be made from a solid steel or aluminium disc with particles bonded to the surface. Today most grinding wheels are artificial composites made with artificial aggregates, but the history of grinding wheels began with natural composite stones, such as those used for millstones.

The manufacture of these wheels is a precise and tightly controlled process, due not only to the inherent safety risks of a spinning disc, but also the composition and uniformity required to prevent that disc from exploding due to the high stresses produced on rotation.

Grinding wheels are consumables, although the life span can vary widely depending on the use case, from less than a day to many years. As the wheel cuts, it periodically releases individual grains of abrasive, typically because they grow dull and the increased drag pulls them out of the bond. Fresh grains are exposed in this wear process, which begin the next cycle. The rate of wear in this process is usually very predictable for a given application, and is necessary for good performance.

Characteristics

[

edit

]

There are five characteristics of a cutting wheel: abrasive material, grain size, wheel grade, grain spacing, and bond type. They are indicated by codes on the wheel's label.

Abrasive Material

[

edit

]

The abrasive aggregate is selected primarily according to the hardness of the material being cut. Chemical compatibility is also a concern. For example, because carbon alloys with iron, silicon carbide is not suitable for use with iron-based metals like steel.[citation needed]

Grinding wheels with diamond or CBN grains are called superabrasives. Grinding wheels with aluminum oxide (corundum), silicon carbide, or ceramic grains are called conventional abrasives.

Grain size

[

edit

]

From 10 (coarsest) to 600 (finest), determines the average physical size of the abrasive grains in the wheel. A larger grain will cut freely, allowing fast cutting but poor surface finish. Ultra-fine grain sizes are for precision finish work. Generally, grain size of grinding wheels are 10-24 (coarse), 30-60 (medium), 80-200 (fine), and 220-600 (very fine).

Wheel grade

[

edit

]

From A (soft) to Z (hard), determines how tightly the bond holds the abrasive. A to H for softer structure, I to P for moderately hard structure and Q to Z for hard structure. Grade affects almost all considerations of grinding, such as wheel speed, coolant flow, maximum and minimum feed rates, and grinding depth.

Grain spacing

[

edit

]

Spacing or structure, from 1 (density) to 17 (least dense). Density is the ratio of bond and abrasive to air space. A less-dense wheel will cut freely, and has a large effect on surface finish. It is also able to take a deeper or wider cut with less coolant, as the chips clearance on the wheel is greater.

Wheel bond

[

edit

]

The company is the world’s best abrasive grinding wheel manufacturers supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

How the wheel holds the abrasives; affects finish, coolant, and minimum/maximum wheel speed.

Bond name Bond symbol Bond description Vitrified V Glass-based; made via vitrification of clays and feldspars Resinoid B Resin-based; made from plants or petroleum distillates Silicate S Silicate-based Shellac E Shellac-based Rubber R Made from natural rubber or synthetic rubber Metal M Made from various alloys Oxychloride O Made from an oxohalide Plated P Made by Electro / Electroless bonding of metal to hold abrasive

Types

[

edit

]

Straight wheel

[

edit

]

Straight wheel

To the top is an image of a straight wheel. These are by far the most common style of wheel and can be found on bench or pedestal grinders. They are used on the periphery only and therefore produce a slightly concave surface (hollow ground) on the part. This can be used to advantage on many tools such as chisels.

Straight Wheels are generally used for cylindrical, centreless, and surface grinding operations. Wheels of this form vary greatly in size, the diameter and width of face naturally depending upon the class of work for which is used and the size and power of the grinding machine.

Cylinder or wheel ring

[

edit

]

Cylinder wheels provide a large, wide surface with no center mounting support (hollow). They can be very large, up to 12" in width. They are used only in vertical or horizontal spindle grinders. Cylinder or wheel ring is used for producing flat surfaces, the grinding being done with the end face of the wheel.

Tapered wheel

[

edit

]

A straight wheel that tapers outward towards the center of the wheel. This arrangement is stronger than straight wheels and can accept higher lateral loads. Tapered face straight wheel is primarily used for grinding thread, gear teeth ...

Straight cup

[

edit

]

Straight cup wheels are an alternative to cup wheels in tool and cutter grinders, where having an additional radial grinding surface is beneficial.

Dish cup

[

edit

]

A very shallow cup-style grinding wheel. The thinness allows grinding in slots and crevices. It is used primarily in cutter grinding and jig grinding.

Saucer wheel

[

edit

]

A special grinding profile that is used to grind milling cutters and twist drills. It is most common in non-machining areas, as sawfilers use saucer wheels in the maintenance of saw blades.

Diamond wheels

[

edit

]

Diamond wheel

Diamond wheels are grinding wheels with industrial diamonds bonded to the periphery.

They are used for grinding extremely hard materials such as carbide cutting tips, gemstones or concrete. The saw pictured to the right is a slitting saw and is designed for slicing hard materials, typically gemstones.

Mounted points

[

edit

]

Mounted points are small grinding wheels bonded onto a mandrel. Diamond mounted points are tiny diamond rasps for use in a jig grinder doing profiling work in hard material. Resin and vitrified bonded mounted points with conventional grains are used for deburring applications, especially in the foundry industry. Mounted points is a small handle with a general name, used in electric mill, hanging mill, hand drill. Many of the main types of ceramic mounted points, rubber mounted points, diamond mounted points, emery cloth and so on.

Ceramic mounted points: granular sand (usually corundum, white jade, chrome corundum, silicon carbide) made of ceramic binder sintering, the central supplemented by metal handle. Mainly grinding all kinds of metal, for the diameter of the inner wall of the grinding, mold correction. Rubber mounted points: finer particle size sand combined by rubber binder Into, for the polishing of the mold. sandpaper mounted points: Multi-piece rectangular sand cloth, bonding around the metal handle. Granularity is generally in the 60 # -320 #, for the diameter of the inner wall of the polishing. Diamond mounted points: A grinding tool for non-metallic materials such as stone, porcelain and the like, and more particularly to a grinding tool using a diamond alloy as a grinding body comprising a substrate and a plurality of grinding bodies, And the substrate is preferably made of an adhesive material having a certain toughness, and the grinding body is preferably made of a diamond alloy material, and the substrate is preferably made of a diamond alloy material, The utility model has the characteristics of high grinding performance, simple manufacture and low cost, high grinding quality and can be applied to large-scale grinding.

Cut off wheels

[

edit

]

Cut off wheels, also known as parting wheels, are self-sharpening wheels that are thin in width and often have radial fibres reinforcing them. They are often used in the construction industry for cutting reinforcement bars (rebar), protruding bolts or anything that needs quick removal or trimming. Most handymen would recognise an angle grinder and the discs they use.

Use

[

edit

]

Grinding produces sparks and little fragments of metal, called swarf.

To use the grinding wheel it must first be clamped to the grinding machine. The wheel type (e.g. cup or plain wheel below) fit freely on their supporting arbors, the necessary clamping force to transfer the rotary motion being applied to the wheels side by identically sized flanges (metal discs). The paper blotter shown in the images is intended to distribute this clamping force evenly across the wheels surface.

Dressing

[

edit

]

Grinding wheels are self-sharpening to a small degree; for optimal use they may be dressed and trued by the use of wheel or grinding dressers. Dressing the wheel refers to removing the current layer of abrasive, so that a fresh and sharp surface is exposed to the work surface. Trueing the wheel makes the grinding surface parallel to the grinding table or other reference plane, so that the entire grinding wheel is even and produces an accurate surface.

Grinding wheels and grinding tools are used extensively in industry and manual trades for treating surfaces and for separating and cutting objects and have to withstand massive mechanical stress. Mostly centrifugal forces can cause a break, but also flexural and shear forces. Since a break or failure of the grinding tool can present a severe hazard to people and machinery due to the high levels of energy released, high standards are placed on the mechanical and breaking strength of grinding tools in the European safety standards. The Institute for Occupational Safety and Health of the German Social Accident Insurance conducts tests based on the "Rules of Procedure for Testing and Certification carried out by the Testing and Certification Bodies in DGUV Test".[1]

See also

[

edit

]

References

[

edit

]

For more information, please visit plier and cutter manufacturer.