In this article we aim to emphasise the advantages of choosing the correct dressing tool for specific applications. Dressing and truing are common terms used in precision grinding applications. Although using the same tool in both instances, each application poses its own unique characteristics.

When a grinding wheel’s form or shape is no longer within desirable limits, and or no longer within the specific tolerance limits of the wheel, trueing known as a shaping process will be applied, this will bring the wheel back into proper form, or shape for its surface to run concentric to the spindle axis of the grinder or to the necessary tolerance requirements.

Dressing on the other hand is a process where the wheel is reconditioned to such an extent that its cutting performance is once again improved. As a grinding wheels’ sharp edges wear away on application, metal particles derived from the workpiece gets loaded into the wheel. To remove these together with the dull grain, “dressing” is required to expose new sharp grains, which restores maximum performance to the wheel.

With the advancement of grain and bonding systems, optimising the overall grinding process is of utmost importance in order to find the perfect balance between cost and efficiency. Choosing the correct dressing tool will reduce overall wheel wear, and aid in maximum wheel performance.

Dressers are available in a multitude of derivatives ranging from abrasive sticks, to single point, multi point, diamond rotary and or star-shaped dressers.

Single point diamond dressers have a single diamond sintered onto a metal shank varying in different sizes from 0.25, up to 1.0 carat. To choose the correct single point dresser, one would consider the size of the grinding wheel, the smaller the wheel, the smaller the diamond, the bigger the wheel, the bigger the diamond requirement. The single point diamond dresser is positioned on the centreline of the grinding wheel and slightly offset to the left, canted between 10 to 15 degrees in the direction of the wheel’s rotation.

The above method aids the diamond from not digging into the grinding wheel, reducing vibration and extending dresser and wheel life. It is however to be noted that single point diamond dresser must be rotated by an eight to retain a sharp point, reducing the change for the diamond to become flat and unusable.

Multi point diamond dressers contain as the word implies multiple diamonds embedded into the metal matrix. This type of dresser is best used on wheels with either straight or tapered surfaces, one of the main advantages of a multi-point diamond dresser compared to that of a single point is that it doesn’t require any rotation. As the diamonds are embedded in a metal matrix they are shelf sharpening, providing longevity of up to ten times more compared to single point diamond dressers depending on the application.

Their bigger surface contact area, allows for them to be used at a faster traverse speed enabling a faster dressing rate. By using a faster traverse speed, the grinding wheels’ surface is open and perfectly suited to rough grinding operations. Where a finer finish is required from the same wheel, the traverse speed should be slowed down, effectively closing the face of the wheel, making it act harder, providing a finer finish.

Star-shaped Dressers, make use of several hardened carbon steel wheels with a special teeth design mounted onto a metal handheld body. The tool is handheld against the grinding wheels’ surface, and as the cutter comes into contact with the grinding wheel’s surface, the cutter begins to spin and act as cutting points that fracture the abrasives grain. Best suited to applications on wheels with coarse grain specifications, such as bench grinding wheels, and grinding wheels specific to pedestal grinders used in a variety of machine shops and foundry fettling bays.

Dressing sticks, are mostly manufactured from silicon carbide and pressed into a rectangular shape. Its application is a handheld operation, whereby the dressing stick is applied to a variety of grinding wheels making use of a fine grain specification. The dressing stick is rubbed along the grinding wheel’s face to remove dulled grain.

Choosing the correct dressing tool will not only improve the surface finish of a workpiece, but also its dimensional accuracy. Effectively extending the grinding wheels’ life, cutting ability and efficiency.

For further information contact Grinding Techniques on TEL: 011 271 6400 or email info@grindtech.com or visit www.grindtech.com