What is a used centreless grinder and what are its benefits? If you are looking for a second-hand machine tool for the most demanding grinding processes, this is the machine you need. Buying a used grinding machine can save you money and is a sound investment.
What is a used centreless grinder?
Among the various machining processes, grinding machines work by abrasion. In other words, as their name suggests, these machines grind the surface of workpieces that have previously been machined on other equipment such as lathes and milling machines and which, because of their characteristics, require specific tolerances.
Grinding machines are machine tools that perform abrasive machining, which uses a cutting tool, the grinding wheel, to remove small amounts of excess material from the surface of a workpiece. The grinding wheel or abrasive wheel is made of an abrasive material, present in the form of small grains held together by a special bonding agent.
Types of grinding machines
Before buying a used or second-hand centreless grinder, it is important to know that there are different types of grinding machines and that each is used to machine different workpieces. The main types of grinding machines include:
- Surface grinders. They are the easiest to use and, depending on the orientation of the wheel, can be face-type or peripheral. The former are used to remove material quickly, while the latter are used for precision work on very simple parts.
- Cylindrical grinders. The workpiece must have a central axis of rotation, and these machines can be external or internal. On external grinders, the outer surface of the workpiece is ground between centres; on internal grinders, the inside of the workpiece is ground.
- Centreless grinders. These machines are used to machine small cylindrical parts.
- Universal grinders. They can machine rotational parts. They are large and very rigid.
How a used centreless grinder works
A used centreless grinder is the machine used for parts that, owing to their characteristics and dimensions, cannot be machined on other machines. On a used centreless grinder you can machine cylindrical parts of very small sizes, such as bushes, bolts and pins; these parts are widely used in the metalworking industry to manufacture other machines.
The operating principle of centreless grinders is based on two abrasive wheels that rotate in the same direction, with the workpiece placed between them. On centreless grinders the workpiece is not held by any clamping system, such as chucks or jaws (hence the name centreless), because the part is so small that it would be impossible to clamp. The workpiece sits between the two wheels and rotates in the opposite direction to them, driven by the regulating wheel, which is inclined at an angle of between 1 and 5 degrees. This inclination depends on the material hardness of the workpiece and on its diameter.
What is centreless grinding?
Centreless grinding is one of several grinding processes and is carried out on the outside diameters of a workpiece. The main difference between this type of grinding and the others is that the workpiece is not clamped at all; on other grinding machines, the workpiece is held between centres or in a chuck that rotates it against the wheel.
Workpieces ground without centres do not require driving or clamping systems. Instead, the workpiece is supported on its own outside diameter by a work rest blade located between the grinding wheel and a regulating wheel. The grinding wheel runs at high speed and has a large diameter; the regulating wheel, by contrast, runs at a lower speed and has a smaller diameter.
Why use a used centreless grinder?
This type of machine tool is recommended when you need to machine parts with very tight tolerances and small dimensions that could not be held in a chuck. Results on these machines are outstanding: if the workpiece is set up correctly, you can achieve excellent roundness, a high-quality surface finish and the required tolerances.
You may be surprised to learn that these machines can also produce round parts from completely flat shapes. This makes centreless grinders highly sought-after machines in the metalworking industry.
And why a second-hand machine? If you are starting up your business or workshop, you may want to invest in a used machine. Used machines are delivered reconditioned and fully operational at a more affordable price than a new machine. You will also receive technical support when needed and preventive maintenance of the machine, and it will be much easier to find spare parts in the event of a breakdown.