Advantages of Metal Bond Grinding Wheels
Every superabrasive grinding wheel consists of diamond or CBN grit held in a supporting matrix material known as the “bond.” The main bonding systems are resin, vitrified, electroplated, and metal. Of these, metal bond grinding wheels are perhaps the best known thanks to their overall utility and the length of time they've been available.
CONSTRUCTION AND MANUFACTURE
Metal bond grinding wheels start life as a superabrasive grit mixed with a metal powder. Most often this is bronze, although other metals such as iron and nickel are sometimes used. The mixture is distributed evenly around the periphery of a metal grinding wheel form, then placed in an oven and heated to around 1,4000F (7600C.) At these temperatures the metal grains begin to melt and diffuse into one another. This creates a dense matrix that locks the abrasive grit in place more tightly than in resin or vitreous bond wheels.
STRENGTHS AND WEAKNESSES
The metal bond wheel structure offers a number of advantages.
Metal bond grinding wheels last longer than those made by other methods. This boosts productivity by cutting down on dressing frequency and wheel changes.
Complex forms can be created, and since wear rates are low they last longer than in other types of wheel.
The metal structure is impervious to attack by alkaline coolants, (unlike resin grinding wheels which are susceptible to chemical attack, especially at elevated temperatures,) so is well-suited to use with grinding fluids.
Has excellent impact resistance, (unlike a vitrified wheel,) thanks to the metal wheel form, so stands up well in interrupted cut applications.
Heat is quickly dissipated through the metal core. This makes it appropriate for high material removal rate operations like creep feed grinding, (which are also helped by the ability to use coolant.)
One weakness to be aware of with metal bonded grinding wheels is that they are not easily dressed. Unlike resin and vitrified wheels, the bond material can't be cut away to release dull grit and expose new edges.
Metal bond grinding wheels can be used on a range of materials such as carbides and tool steels. However, their main application areas are those where coolant is needed to remove heat and chips, such as grinding or cutting glass, ceramics, granite, stone and concrete. They are usually recognizable by the presence of the metal core, but the 'M' at the end of the wheel identification code should remove any doubt.
The main advantage of these wheels is their long life/low maintenance nature. This makes them ideal for use when productivity concerns are paramount. Their ability to dissipate heat and work with coolant means they are useful in situations where interface temperatures become high enough to cause burning or size control problems. They are particularly useful in creep feed and internal grinding and also find use in grinding complex forms as the shape is maintained over the course of a long production run.
Purchasing diamond or CBN grinding wheels is a significant investment, so it's important to select the type of construction most appropriate to the intended application. Metal bond grinding wheels are perhaps the best known type but it may be worth seeking advice from specialists at CDT before ordering.