Grinding - finishing the metal surface: grinders, machines

The most efficient technological operation, that allows to bring a surface of details from metal to an ideal condition, there is grinding. Details, the surface of which was subjected to such a procedure, may form airtight or tight connections. The need to form such connections and, in accordance, in technological operation, performed with special tools and materials, is in many areas.

Finishing the blade of the plane on the grinding bars

the essence of technology

Grinding, thanks to which it is possible to receive surfaces with necessary degree of roughness and with the set deviations, involves removing a thin layer of metal from the workpiece, for which, in contrast to the finishing operation of the scraper, not only tools are used, but also fine abrasive powders or pastes. Abrasive material, by which such processing is performed, can be applied as on a surface of a detail, and on a special device, which is called grinding.

schemes of proof

Grinding, performed at a slow speed and with constantly changing the direction of movement, allows not only to reduce the surface roughness to the desired value, but also significantly improve its physical and mechanical characteristics.

Grinding, which is often called proof, can be performed in different ways. So, details of complex configuration, manufactured in single copies, processed completely by hand, and for grinding products, available in small series, use a semi-mechanical method. At the same time giving of a detail in a processing zone is carried out manually, and grinding itself is performed using mechanical devices. In the production of parts in large series and en masse can not do without such a device, as a lapping machine, by means of which and carry out finishing operations.

Position of hands when grinding metal surfaces

Special devices and materials

As mentioned above, to perform grinding or finishing, special tool required, which is called grinding. By the shape of the work surface, such devices are divided into the following types:

• flat grinding tool;
• with an inner surface of cylindrical type;
• with an outer cylindrical surface;
• conical tool.

Pneumatic lapping machine for finishing valves

Choosing a material for making a lapping tool, pay attention to that, that its hardness was much lower, than the hardness of the material of the workpiece. This requirement is due to the topic, that abrasive powder or paste, using which perform grinding, could be held by the material of the tool. So, the most common raw material for the manufacture of such devices is:

• gray cast iron;
• copper;
• lead;
• mild steel;
• different species of wood;
• other metals and non-metallic materials.

Special grinders for optical sight sleeves

To perform preliminary and finishing grinding operations, the tool is used as a different design, and made of different materials. Example, to perform previous operations, when using abrasive material of a larger fraction, a tool made of softer materials is used. On the working surface it is pre-cut grooves to hold the abrasive, the depth of which is 1-2 mm. Finishing of products, performed with a fine abrasive, carried out by the device, the working surface of which is absolutely smooth. The material of the tool for finishing operations, mainly cast iron. With the help of grinding tools, which are made of lead and wood, the surfaces of the workpieces are glossy.

Set for manual grinding, consisting of cast iron grinders and diamond paste of different grain sizes

Abrasive powder is the main material, which ensures the efficiency and quality of grinding. Such powders, depending on the material of manufacture, divided into solid (the hardness of the material is higher, than in hardened steel) and soft (their hardness is lower, than in hardened steel). Corundum is used to make powders of the first type, carbocorundum and emery, and the other chromium oxide, Viennese lime, crocus and others. According to the degree of granularity, abrasive powders are also divided into several categories. You can distinguish powders and pastes of different categories from each other even by their color. So, paste, based on coarse powder, have a light green color, medium grain - dark green, paste with fine powder - greenish-black.

The most famous variety of pastes of the latter type, with which to perform finishing lapping operations, there is a GOI paste.

Many homemakers, engaged in metalwork, independently make powders and pastes for grinding. This is quite easy to do: for this purpose it is necessary to grind carefully pieces of an emery wheel in a massive mortar, and then sift the resulting powder through a sieve with very small cells.