Bonded Abrasives / 219 www.nortonabrasives.com These bonds are used in two types of wheels. Firstly, wheels used on portable or fixed machines for the rapid removal of metal. Secondly, cutting-off wheels either un-reinforced or reinforced, for use on portable or fixed machines. The most common organic bonds are: SNAGGING WHEELS & CUPS B & B3 Foundry wheels: multi-purpose bond that gives satisfactory results on most applications B28 Foundry wheels: high level bond suitable for most technical applications requiring high powered machines CUTTING-OFF WHEELS BFX Foundry X bond technology designed to increase cut rate and wheel life in all cut-off applications on a wide range of tough materials BF1 Specific bond ensuring the best quality of cut in dry or wet conditions BF3 New generation bond assuring the best wheel life in dry cutting operations; versatile and long wheel life. Ideal for heavy duty operations B24 New generation bond used on silicon carbide cut-off wheels that gives the best performance and the ultimate cut quality on non-ferrous metals in wet conditions B25 Standard multi-purpose bond that offers durability and freeness of cut in a wide variety of materials and applications. Can also be used in wet cutting on softer grades B26 New generation bond used on aluminium oxide cut-off wheels that gives the best performance and the ultimate cut quality on ferrous metals in wet conditions B65 Traditional bond gives good performance and long wheel life in dry cutting conditions BOND TYPES-ORGANIC SELECTING THE RIGHT PRODUCT THERE ARE NINE MAIN FACTORS TO BE CONSIDERED WHEN SELECTING A GRINDING WHEEL FOR ANY APPLICATION: • The material to be ground – its type and hardness • The stock to be removed • The workpiece geometry and surface finishes required • The grinding machine, the type of machine, the power available and its conditions • Wheel speeds and feeds • Grinding contact area • Grinding fluid – whether the operation is wet or dry • The severity of the grinding operation • The dressing method MATERIAL TO BE GROUND The type of material affects the selection of abrasive, grit size and grade. Alumina type abrasives are the most suitable for grinding high tensile materials such as steel and ferritic cast iron. The more friable types of alumina are preferred on harder steels and applications having large arcs of contact. Low tensile strength materials and non-metallic materials are most efficiently ground or cut with silicon carbide abrasive. The hardness of the material governs the amount of penetration that can be achieved by the abrasive. For this reason, finer grit size wheels are required to grind hard materials and soft materials are best ground with medium to coarse grit size wheels. For most efficient operation, the grade must be adjusted to suit the hardness of the material. As a general guide, the harder the material, the softer the grade of wheel required. STOCK TO BE REMOVED This affects the choice of abrasive size and bond type. High stock removal rates, as in fettling operations, require coarse grit wheels, typically 12 to 24 mesh. Fine finishes and tight limits on finished workpiece geometry require finer grit sizes. Final surface finish is often achieved by ‘spark out’. No further infeed is applied and the wheel is allowed to grind until the majority of the grinding sparks cease. BONDED ABRASIVES
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