Surface grinding is an abrasive process. It involves securing the object to a device that will hold it in place (a chuck) before slowly moving the object's surface across a grinding wheel that's spinning really fast. This will generate a flat plane wherever the machine comes into contact with the object. It also gives the object an even finish. The longer the wheel spends working on the cutting depth, as well as using a surface grinding wheel with a higher grit count will further improve the surface's finish. By slowly increasing the depth of the cut the machinist will be able to achieve these things.
The surface grinding machine is the most common type of grinding machine found in any shop. You can actually compare it to milling cutter that has multiple teeth but the surface grinding machine has a grinding wheel, which makes it an abrasive cutting tool. The wheel is used to remove really small pieces of metal (known as swarf). It works because the wheel is made up of thousands of cutting edges.
These surface grinding tables are used for several different purposes including removing excess material. They work really well on very hard materials (i.e. steel, diamonds) to produce a very high quality finished surface.
The surface grinding machine's chuck moves back and forth once the table has raised the object so that it's slightly deeper within the wheel. There are intervals that can be set (i.e. 0.001 inches / 0.0254 mm) with each pass. As the grinding wheel rotates with its abrasive particles small amounts of the object's material will be removed each time in order to create a flat surface. For this reason, the surface grinding process is usually a finishing step that's designed to bring an object to a certain tolerance but the procedure is often followed up with a polishing procedure during the grinding-and-lapping process.
Over the course of time, the surface grinding machine has evolved. Today there are even some machines that are ergonomic, as well as those that are portable. Computer Numerically Controlled (CNC) grinders are also available. Regardless of the type of machine you choose to use, it will be controlled by a computer interface today.
There are 2 types of abrasive materials that are used within the grinding wheel:
1. Aluminum oxide is used whenever the materials that are being ground have a high ductility or the ability to permanently become deformed.
2. Silicon oxide is used whenever the materials that are being ground have a low ductility.
Regardless of what type of material you're grinding (i.e. steel, aluminum, glass) the machine's abrasive grains will allow for a smooth finish. Usually these abrasive grains are coated with diamonds.
A grinding wheel has a doughnut-like design. The hole in the middle slides down over the top of a metal rod (spindle). Today these machines are being made by lots of different manufacturers and so there are a lot of different models available to choose from. Nevertheless, they still use one of the following types of structure:
1. A vertical spindle design has a spindle that's pointing straight up and down. The grinding wheel itself lays flat on its face at the bottom of this spindle so that the wheel's full width can be utilised in grinding the object. Typically, this type of design is used whenever working on larger panels or sheets of materials or whenever there's a lot of materials that need to be quickly ground.
2. A horizontal spindle design has a wheel that's suspended over the table. Only the wheel's flat, outside edge will come into contact with the object that's being secured by the chuck. Thanks to the smaller grinding surface it's possible to have great precision whenever you're making a cut, which is why they're typically used whenever small features (i.e. angles, profiles) are needed.
In the same way as there are 2 common types of spindles, there are also 2 common types of surface grinding machines, both of which only grind flat surfaces. These include:
1. Planer grinders keep the grinding wheel in one place while the worktable around it is being moved, creating a reciprocating back-and-forth motion that can be controlled either manually or via a mechanic or hydraulic drive mechanism. The spindle that's used to rotate the grinding wheel can be placed either vertically or horizontally.
2. Rotary-type grinders have circular shaped worktables that revolve, as does the grinding wheel itself. They can be either vertical or horizontal.