Vitrified is the most recently developed bond and has some very specific advantages for internal, external, centreless, surface, creepfeed, disc or any grinding application where high precision is required. The easily adaptable structure of the grit bond matrix usually allows truing and dressing in one operation.
Vitrified bondings are basically composed of glass. The bondings are mixed in powdered form along with the CBN or Diamond abrasive. Each component of the mix is precisely determined by the required characteristics of the finished wheel and are tightly controlled in the process. The resulting bond is tough and wear resistant, which makes vitrified bonded wheels ideal for extended wheel life and form holding.
One of the unique properties of vitrified bonds is porosity and the ability to “self-dress”. The porosity of a vitrified wheel provides better flow of coolant into the grind zone and improved clearance of chips. This allows a vitrified wheel to cut considerably faster than other non-porous bond systems under the same grinding loads. The porous structure and brittle nature of vitrified bondings also eliminate the need for stick dressing in most applications.
While the wheel is dressed with a rotary Diamond, small micro fractures are introduced into the bond posts near the surface of the wheel. When the wheel begins to grind the first part, the chips that are produced easily clear away the top layer of bonding, which exposes the sharp abrasive particles beneath. This is not possible with resin or metal bonded wheels. This characteristic of vitrified bonded wheels makes them ideal for high-production CNC grinding applications where operator intervention is kept to a minimum.