HOLD the grains together with varying degrees of strength.Standard grinding wheel bonds are silicate, vitrified, resinoid, shellac, rubber and metal.Rubber BOND (R): Rubber-bonded wheels are extremely tough and strong.Their principal uses are as thin cut-off wheels and driving wheels in centerless grinding machines.They are used also when extremely fine finishes are required on bearing surfaces.Silicate bond (S): This bonding material is used when the heat generated by grinding must be kept to a minimum. Silicate bonding material releases the abrasive grains more readily than other types of bonding agents. This is the softest bond in the grinding wheel.Vitrified bond (V): Vitrified bonds are used on more than 75 percent of all grinding wheels.Vitrified bond material is comprised of finely ground clay and FLUXES with which the abrasive is thoroughly mixed.Resinoid bond (B): Resinoid bonded grinding wheels are second in popularity to vitrified wheels.The phenolic resin in powdered or liquid form is mixed with the abrasive grains in a form and cured at about 360F.Shellac bond (E): It's an organic bond used for grinding wheels that PRODUCE very smooth finishes on parts such as ROLLS, cutlery, camshafts and crankpins.Generally, they are not used on heavy-duty grinding operations.Metal bond (M): Metal bonds are used primarily as binding agents for diamond abrasives.They are also used in electrolytic grinding where the bond must be electrically conductive.