Honing is what? How is the honing of the cylinders?

Those who work as a machine operator or study in this specialty have often faced with such a concept as abrasive processing. This type of work includes the most popular operations, such as grinding, polishing, superfinishing (superfinish) and honing.

Honing is a specific form of fine processing. It is rarely used in mechanical engineering, as there are other mechanical operations with which you can achieve better results. Therefore, very few people know how honing of cylinders is performed, what it is, what it is used for and in what cases.

Honing: concept and definitions

Honing is a mechanical operation for processing material by cutting, where diamond grains are used as a cutting tool. This operation is considered very efficient and effective in relation to the holes. Remove allowance for this treatment can be up to 2 million mm ³ per hour. This corresponds to a fine turning by the tool during turning or rough grinding with an abrasive wheel. Therefore, it can be said that honing is also a finishing treatment, since during the operation a final surface is obtained, that is, a finished part.

Honing tool

The tool that is used for honing is called hon, or honing head. Chon is a metal-cutting tool consisting of three or more abrasive stones (stones) located along the perimeter.

In many hons the stones are removable. That is, when worn or broken, they can easily be replaced.

Honing machines

In the production of honing performed on special machines, which are of two types: horizontal and vertical. Horizontal honing machines are performed with a horizontal spindle arrangement. Vertical, respectively, have a vertical spindle arrangement. The former are used for long parts, as well as for outdoor operations. Vertical machines - for short parts and mainly for internal processing, i.e. holes.

Known models of machine tools: 3Г833, 3К833, 3Н-86, М4215-1. And also new models: Sunnen HTS-124-020, LEV125 СОМЕС, LEV250 СОМЕС, ТН170 and ТМ806 (807).

Often, new models of honing machines are made specialized, rather than universal, as opposed to Soviet-made machines. That is, they are suitable only for one operation, for example, for honing cylinders. There are also new models of small machines. As a rule, such machines are developed for honing at home.

When is honing applied?

As it was said before, often such a mechanical operation as honing is used to finish the holes and other round hard-to-reach surfaces in those cases when the other methods of abrasive processing can not be applied or their application will be impractical. In addition, honing holes is used in cases where it is necessary to achieve a minimum roughness and cylindrical surface, up to microns. That is why the greatest popularity of this type of processing received in the manufacture of cylinders. The latter are widely used in engineering, construction and automotive industry.

Advantages of honing

Although grinding, polishing and lapping are considered the most popular and common methods of processing cylinders, in most cases preference is given to honing, since it is more efficient and accurate. In addition, when honing, you can face other benefits, including:

1. Increased resistance to wear. This, in turn, positively affects the further operation of the engine and allows maximizing its service life.
2. Absence of marriage details. The fact is that when the cylinders are processed with holon, the surface is subjected to a lower pressure than, for example, when grinding. That is, the chances of obtaining a marriage cylinder are significantly reduced.
3. Achievement of technical requirements. Due to the fact that the honing stones have a wider range in comparison with the same abrasive wheels, it is several times easier to achieve the technical requirements for the workpiece.
4. Making an exact hole. Due to its design, the hone during machining can automatically correct the hole deviations from the allowed values that remain from previous operations, for example, after drilling.
5. Reduces the time allotted for processing. As is known, there is not one device for honing cylinders. There are also such devices that allow you to perform honing of the block of parts. By processing several holes simultaneously, the time taken for the operation is reduced. This is especially important in mass production, when thousands of cylinders are to be manufactured per day.

Honing the cylinder block

As it was said before, in order to perform honing of several cylinders in one operation, at many enterprises a special device for honing is used. Often these are clamping devices that help to secure the cylinder block on the machine bed for subsequent processing.

Thus, after fixing the assembly in the tool on the machine, honing the cylinder block is performed in two stages:

1. Draft honing. At this stage of processing, hon is used with coarse-grained bars. With this tool, you can provide the initial, circular shape of the cylinder bore that does not yet meet the technical requirements.
2. Finishing honing. Instead of the hone with coarse-grained blocks, a fine-grained abrasive is now used. It can be diamond or ceramic bars. The essence of the second stage is to eliminate the final allowances and create a ready-made hole shape that will meet the technical requirements for the part.

Honing at home

Few know that honing cylinders can be carried out not only in the factory, but also at home. Often such an operation may be necessary in those cases when the old cylinder block has lost its property of resistance to wear or it needs to be cleaned of the accumulated scale.

At home, honing is still the same fine treatment, but not with the use of coolant and hone, but with kerosene (or honing oil) and a special honing head, which is easily attached to a conventional electric drill. Such heads can be purchased in any automobile or building shop (they look like brushes for washing dishes). As in the case of hons for machine tools, honing heads for drills are also sold for roughing and finishing. They differ among themselves by the permissible diameters and material.

To perform this operation and for more comfortable handling, the cylinder block can be fixed in any clamping device or, at least, on a surface that can be restrained by feet. After the part is securely fastened, you can carry out honing yourself. It is recommended that the hole be treated twice during roughing and once with a finishing one.

Cleaning the surface of cylinders

After performing the honing operation, as a rule, you should clean the part from the metal shavings and abrasive. Effective cleaning will allow warm soapy water and a soft brush. Thus, it is possible to save the part not only from chips, but also to polish it.

After all of the above, the cylinders are usually further processed with a special abrasive paste. It allows you to clean the surface of the remaining small chips, which is difficult to notice with the naked eye.

Using soapy water, brushes and pastes for cleaning allows you to restore the previous view of the block of cylinders, get rid of any burrs, scale, etc.

Finally

Having learned how the re-honing of cylinders is performed, what it is, when it needs to be used, many may think that this is a fairly simple procedure and, perhaps, not even absolutely necessary. But, despite the simplicity, the effect of re-processing cylinders honing will not take long.

This processing will help extend the life of both the unit and the car. In addition, re-honing at home will help improve maintainability without the need to refer to the appropriate specialists.