TYPES OF GRINDING MACHINES
Different types of grinding machines have been designed and are being used. Some of these are for roughing work, some for precision work and some for special purpose i.e. to perform a specific type of operation only. There are many varieties of grinding machines; the most commonly used types can be classified as:
A. Roughing or non precision grinders.
B. Precision grinders.
1. Roughing or non Precision grinders:
The main purpose of these grinders is to remove more stock than can be removed by other types of grinders.
The quality of surface finish is of secondary importance are as follows:
1. Bench, pedestal or floor grinders.
2. Swing frame grinders.
3. Portable and flexible shaft grinders.
4. Belt grinders.
1. Bench, pedestal or floor grinders:
These grinders are commonly used for grinding various materials and cutting tools in tool rooms, foundries and general repair shops etc. They carry horizontal spindle, having grinding wheels mounted on both ends. It can be suitably bolted on a bench.
The floor stand or pedestal grinder is bench grinder of above type mounted on a steel stand or pedestal of suitable height. The horizontal spindle carrying the grinding wheels is normally an extension on both sides of the armature shaft of the motor. These grinders can also be used for polishing by replacing the grinding wheels by polishing wheels.
2. Swing frame grinders:
It consists of a 2 to 4 meters long horizontal frame, freely suspended at its centre. The frame carries a grinding wheel at its one end and motor at the other. The motor drives the grinding wheel by means of a belt. In operation, the motor is started to revolve the wheel and the frame swung by the operator about its point of suspension (centre point) to cover up the desired grinding area.
3. Portable and flexible shaft grinders:
These grinders resemble very much with the portable electric drills, both in construction, as well as operation, with only difference that the spindle carrying the drill chuck is replaced by a spindle on which a small grinding wheel is mounted. A safety guard is also provided over the wheel. These grinders are vastly used in finishing casting, forgings, welded joints in structural work, removing burrs and sharp edges.
Flexible shaft grinders consist of a flexible shaft driven by an electric motor. The shaft carries a chuck or collet at its end to receive small grinding tools, mounted wheels and points and small grinding discs. The electric motor is mounted on a fixed stand.
4. Belt grinders:
These machines are designed to use an endless abrasive belt for grinding instead of a regular type of grinding wheel. The belt runs round the pulleys or rollers and the work is fed against the revolving the abrasive coated belt. One of the rollers (driver) revolves at high speed.
A heavy metal plate called platen is so incorporated that the smooth under side of the belt runs in contact with the same. This platen may carry the shape conforming to the shape of an object or may be flat as required. The work piece is fed manually on to the open abrasive side of the belt and pressed against the platen to perform the grinding operation. With proper selection of proper grade and grit size, this process can be used both for rough and finish grinding.
Machines are available in different varieties like wet-belt, dry-belt, combination machines etc.