Centerless Grinding – Differences Between a Centerless Grinder and a Hard Commutator

Centerless grinders are a popular type of power grinders that are often used by carpenters. They can be used for both grinding and polishing aluminum, brass, copper, stainless steel and other types of metal. The most commonly used types of materials in centerless grinders are aluminum and steel. There are two main types of grinding wheels: permanent magnetic and electromagnetic.

Centerless Grinder

A permanent magnetic centerless grinder is one which has a large disc of steel surrounded by a magnetic field. This field contains electrical charges which induce a rotation within the steel disc. Because the work piece moves against the rotating disc, any slag or material which can be ground away automatically flows into the grinding area. This type of grinding wheel regulates its own operation by having two sets of rollers with a stopcock between them. When the two rollers near each other there is a momentary electrical magnetic field created which prevents the material being grinded away.

An electromagnetic centerless grinder works in much the same way. However, the electrical charges generated by the machine are carried out both through the workpiece and also into the workpiece itself. This means that the workpiece acts as a source of continual electricity which causes the workpiece to be heated to the appropriate temperature for the desired surface finish. Electromagnetic motors are able to provide a consistent and reliable source of workpiece heating.

Both types of machines use a pair of fixed ceramic plates for holding the work piece stationary. When the workpiece is turned, either wheel provides a stationary lift which lifts the workpiece to the desired height. The second wheel is then engaged in a chuck which has teeth designed to grind the material. There are many variations on both these basic designs, but in general they consist of two wheels and a chuck. The two-wheel design is almost universally preferred, since it results in a substantially more compact overall design.

The two wheels also differ in the way they are designed to operate. In addition to providing lifting action on the worktop surface, the two wheels on a centerless grinders are also geared to regulate speeds. In order to allow the motor to maintain a fixed speed, the speed regulating roller is mounted inside of the operator’s workers. This allows for a constant speed regulation, regardless of the speed of the commutator bar. The most common style of speed regulating roller is mounted directly beneath the workers, but some designs also feature a threaded adjusting rod which can be attached to the commutator bar for faster adjustments.

A final distinction between an electro-hydraulically operated centerless grinding machine and manually operated one centers around the type of material which is being grinded. Electro-hydraulics are used to grind soft metals such as aluminum or copper, and typically result in faster turning speeds and more economical operation than their counterparts. Merely having a grinding wheel attached to a centerless grinder by means of a commutator does not constitute an electro-hydraulically operated piece, since it is not technically a “grinding” machine at all. This distinction is often illustrated when a centerless grinder is utilized to cut soft materials such as fiberglass, which must be ground in a similar manner to its metallic counter component.