Honing engine cylinders. what is it and why is it made?

Processing tool

For processing, a special honing tool is used - honing. Honing heads are classified according to the following characteristics:

• according to the method of fastening the abrasive tool: rigid;
• floating;

according to the method of ensuring the size:

• adjustable;

self-unclosing.

The honing head consists of:

1. housings;
2. abrasive bars;
3. rod;
4. control coupling.

The body has milled grooves into which abrasive stones are installed. A collet mechanism is provided inside the body, ensuring simultaneous and smooth ejection of the bars.

The coaxiality of the motor sleeve and the tool is ensured by the rod. The resulting hole diameter is adjusted using a coupling.

Description

Purpose

It is used for finishing the working surfaces of internal combustion engine cylinders, brake cylinders and other internal cylindrical surfaces that require precise geometric dimensions and roughness parameters.

Description

• For cylinders with a diameter from 32 to 89 mm • Hon grain size: 220* • Cylindrical shank with flexible extension • Spring-loaded hone supply mechanism • Spring stiffness adjustment nut

* a set of replacement hones (stones) is also supplied separately.

Honing is a process of treating a metal surface using diamond chips. It is mainly used for grinding conical and cylindrical parts. This operation is convenient when making holes. The resulting surface roughness value corresponds to the level of fine turning or grinding with a coarse-grained abrasive wheel. Only the honing method can achieve the desired result when working with a cylinder block. At the interfaces between parts there must be lubricant, which is held in place by a specially applied honing mesh.

The honing tool used is called a hone. These are bars or stones that are placed around the perimeter of the base. During operation, they are erased, so the design of the clip allows for the possibility of replacing them.

Special machines are used for the honing process. These are devices with a horizontal or vertical arrangement in the spindle space. Each of them has its own purpose depending on the work being done. Honing equipment is specialized for narrow profiles. The production of universal machines is a thing of the past.

What car owners say about cylinder honing

1. Honing on old engines Honing the cylinder block at Soviet enterprises in the 60–80s. was absent in principle. Automobile, boat and motorcycle engines were, as a rule, the result of side activities of the defense industry. Therefore, there was no incentive to introduce new technologies and improve existing products. People bought what was available and did not complain about the quality, because there was always a shortage and long queues for almost any product, including cars. The complication of technological operations was not welcomed in mass production, and in the absence of competition, the plant did not care how long its engine went through before a major overhaul.
2. Non-factory honing A homemade hone may be no worse than a factory one, but the difficulty is that there is no information anywhere about the depth of the grooves, the honing angle, and the permissible surface roughness.
   These parameters greatly affect the quality of lubrication and oil consumption. Oil starvation, as well as high consumption, will not make the engine long-lived. Increasing the honing pitch can lead to a reduction in oil film thickness and rapid engine wear. Therefore, car services, when honing a cylinder block, make certain average indicators that are suitable for a given type of engine (3L V6, for example). A lot depends on the machine equipment used. In boxer engines, the cylinder axis is horizontal, and therefore there is logic in changing the grid pitch and hone angle at the top and bottom of the cylinder.
3. Advantage of factory honing Repair honing of cylinders is significantly worse than factory honing. Flat-top honing can only be achieved in automotive production conditions. Car repair shops will not be able to handle such equipment, and the manufacturer has no interest in doing major repairs efficiently. When cutting a furrow with a hone, a turning and boring machine squeezes out a layer of metal on each side, which wears out the rings much faster during engine break-in.
4. Honing Wear Uniformity Hon wears unevenly. Maximum wear occurs at the position of the upper compression ring at TDC of the piston. Above it, wear is significantly less.
5. Same hone or different The honing angle is different for each engine and each manufacturer. It’s difficult to find exact numbers; you often have to look at how it’s done on similar engines. Once I was rebuilding the engine on a RAV4 using a manual hone. In appearance it is much worse than the factory one, but it still gives the effect. After manually honing the cylinder block and replacing the rings, oil consumption practically disappeared.

Honing or grinding cylinders: which is better?

Both procedures are similar at first glance, but they are fundamentally different things. Grinding creates a mirror of the cylinder, this concept means ideal smoothness of the surface (without honing marks). The mirror is created during long-term operation of the engine, in other words, it is stuffed. Grinding in a workshop is used in the following cases:

1. If the deformation of the cylinder head has led to a violation of the overall geometry and strength of the engine structure.
2. Welding work was carried out.

On a note! Honing differs from creating a mirror by applying a grid of marks. A smooth surface holds oil poorly, resulting in increased oil consumption.

A honed cylinder is protected from excessive oil consumption and operates more stable than a mirror cylinder. If the hone mode was chosen correctly, and the exact angle of operation was maintained, the engine will work better and last longer.

Carrying out work

To obtain a high-quality result, a honing machine is required. Such equipment is used in large specialized auto repair shops that repair diesel and gasoline engines.

The cylinder block is positioned and secured on the machine table so that the holes or liners are positioned strictly vertically. This is the main condition. The honing head is placed inside. The clutch adjusts the desired hole size.

The processing process is carried out using working fluids. Kerosene is used to process cast iron, and a mixture of kerosene and oil is used to process steel. Coolant emulsions are increasingly being used. For example, 7% aqueous solution of NSC-5.

Interestingly, during honing, the surface is hardened to a depth of 0.06 mm. When the pressure of the abrasive bars is equal to 5 kgf/cm2, the hardness increases by 10−15%. When processing alloy steels and a pressure of 70 kgf/cm2, the hardness value increases to 70%.

Caseless engines

Hone treatment differs on liner and linerless engines. If you need to process a linerless cylinder block, there should not be any particular difficulties.

The solid metal structure is securely fixed to the machine table immediately after the boring process. You should make sure that the sleeves are positioned strictly vertically and that no displacements will occur during the reciprocating movement of the cartridge - otherwise there will be no benefit from the processing.

When machining linerless cylinders, only a few machine passes are required.

In this case, it is necessary to strictly control the resulting dimensions and surface roughness. An indicator bore gauge (monitors dimensions) and a profilometer or optical device for measuring the level of roughness will help with this.

But why "Mechanics"?

We mentioned above - and for good reason. He is a recognized expert in engine repair. And here are the arguments.

Automotive engines are changing rapidly. The power increases while the size of the unit is reduced. Thermal and mechanical stress on parts is increasing. This means that structural materials for piston rings, pistons and cylinder blocks are being improved. The rings themselves also change - their height decreases, and the number of rings decreases.

You need to know all this, continuously monitor all industry news, and above all, innovative solutions from engine manufacturers.

So, Mekhanika employees keep their finger on the pulse of the global automotive industry. But classical technologies are not forgotten either. Therefore, both the good old naturally aspirated engine and the newest turbocharged unit, born under the downsizing banner, will be repaired here.

As already mentioned, accurate diagnostics are carried out here. This means choosing the right repair technology.

This company has an excellent machine fleet, including modern Sunnen honing machines. And experienced craftsmen work for them. These will not “loose” tolerances; they feel the metal intuitively.

(photo: BC honing machine)

The tools - honing stones and brushes - are imported here. Cutting fluid (coolant) of the highest quality. It washes the instrument and block during the operation, is immediately filtered and again supplied to the working area.

What to do if seizures appear in the engine

It was already noted above that bullies must be dealt with immediately. If you ignore the problem, the condition of the motor will quickly deteriorate. Wear will increase: a small malfunction will cause the next one. Problems will grow like a snowball.

If the scuffs are still very small

When the seizures are very small, you can solve the problem without disassembling the engine. If wear does not exceed tenths of a millimeter, buy and add a special additive to the oil, for example, Active Plus from the Russian one.

This product forms a metal protective film on friction pairs. The special structure of the layer allows you to restore worn surfaces (with small deviations from standard dimensions and geometry).

It is necessary to strictly follow the instructions, both when using the Suprotec tribo composition and when using products from other manufacturers. Exceeding the permissible dose may lead to the opposite result. Even if there is no harm to the mechanism, you will simply be wasting your money.

Suprotek Active Plus additive in engine oil

Restores compression, reduces fuel consumption and oil waste, reduces wear rate and extends the life of internal combustion engines of any type. Facilitates cold starts and protects against overheating in traffic jams.

When additives don't help

If the use of additives does not give the desired result, then the scuffing is already too large. In this case, boring and honing of the internal combustion engine cylinders is required. This operation can be ordered from a car workshop, or performed independently.

You should only undertake honing cylinders yourself if you have plumbing skills. It is necessary to maintain high precision: the pattern formed on the metal must be uniform, the strokes must converge at the same angle.

For this work you will need a special honing device - honing. Two types of these devices are produced - in the form of a “brush” and in the form of a structure of three bars on a central rod. In garage conditions, it is better to use a brush. The grinding stone attachment is more suitable for boring machines.

1. The hone needs to be inserted into the drill chuck. To ensure accurate orientation, you need to use at least the simplest devices: a feed rail and a level. If the accuracy of the stroke is violated, the honing will be defective. We'll have to redo it.
2. Throughout the operation, it is necessary to ensure that the surface being treated and the cylinder honing device are irrigated with a sufficient amount of lubricating fluid. As a rule, kerosene or its mixture with oil is used.
3. Upon completion of the operation, it is necessary to clean the engine from chips and remaining abrasive material. Use a soapy solution to wash away any solids. When the walls are dry, treat them with a special oil that prevents corrosion.
4. After honing, it is recommended to give the engine some time for the cylinder-piston pair to break in. During this period, overload should be avoided and the quality and volume of engine oil should be closely monitored.

To make the running-in process better and more gentle, you can use the tribocompound Suprotec Active Plus and an analogue. The advantage of a product made in Russia is its reasonable price. In terms of operational characteristics, Suprotek Active Plus has no foreign analogues.

The main advantage of do-it-yourself honing is that the engine does not have to be removed from the car. This greatly reduces the operation time. At the same time, it should be remembered that if the cylinders have a high degree of wear, this measure will not help - boring, polishing and then honing are required.

Boring and honing stages

The problems described above entail repair of the power unit. If this is not done on time, the condition of the cylinders may adversely affect the performance of other mechanisms, which will lead to more serious breakdowns. There are cases when, as a result of postponing repairs, it was necessary to replace the entire crank mechanism.

The repair takes place in several stages:

1. The worker bores all the liners in accordance with a certain repair size. If repairs have never been performed before, boring is done to the first size. Be sure to allow a few millimeters of allowance.
2. Honing is performed to give the liners the correct shape and to reduce roughness.

Boring and honing is carried out in stages:

1. First, rough processing occurs. It is made using coarse abrasive materials. The original form is returned.
2. The cylinder is bored using a special abrasive. Honing occurs using diamond or ceramic coated timber. The stone is located on the honing head, which rotates and performs upward and downward movements. This device makes it possible to have high accuracy during the honing process. Scratches are removed from the surface of the cylinders using abrasive materials, so an acceptable degree of roughness occurs.
3. At the end of honing, the surface of the treated cylinder is cleared of debris.
4. Some specialists clean the surface using a special paste.

Cylinder honing and the meaning of this process

How to cut a profile pipe
Many specialized auto repair shops practice honing cylinders

An important goal, as you already understood, is to reduce the roughness for the connection between the piston and cylinders. During its operation, the engine loses its initial properties, as a result of which difficulties arise during its operation

The engine component, as well as its parts, begin to deform

Paying special attention to the cylinder when it is in cross-section, you will notice that its shape is in the form of an oval. When performing repairs or frequent use, scratches and marks may remain on the surface of the cylinders.

In this regard, the following problems arise:

1. Compression properties are lost.

2. Lubricant and fuel costs increase.

3. Engine speed is reduced.

For these reasons, it is imperative to repair the engine. This must be done at the right time, otherwise the appearance and performance of the cylinders may directly affect the functioning of other mechanisms. What can cause a malfunction. There are situations in which, due to the transfer of repairs, it was necessary to install a new crank mechanism.

The part is restored in a couple of stages, such as:

· The master bores all available liners in relation to the subsequent repair parameter. In case repairs have not been made before, the boring is done to the minimum size, this is the first

It is very important to create an extra allowance of a couple of mm

· Honing is carried out to ensure that the liners have the correct shape, and so that, in turn, the roughness is reduced.

Professional Services

If the wear is already significant (for example, when the ellipse of the cylinder exceeds 0.1 mm and the taper exceeds 0.2 mm), it is necessary to bore the cylinders to repair size. In this case, you need to buy special pistons, the diameter of which is larger than the standard ones. The cylinder block must be bored in a specialized workshop. It is impossible to perform this operation in a garage environment. Accuracy tolerances are very strict - tenths of a millimeter. Only professionals equipped with modern equipment can perform this work efficiently.

How is boring done?

At the first stage, the sleeve is bored at low speed. Due to the high strength of the alloy, high speeds are contraindicated - accuracy will suffer. When processing metal at low speeds, the top layer is subject to structural damage, so it must be removed. This is why honing is needed. This technological operation allows you to correct minor flaws that are inevitable when boring. Honing treatment allows you to bring the cylinder bore to a perfectly round shape (with proper honing, the ellipse is no more than 0.03 mm).

Honing after boring is performed in two stages. First, the walls are treated with coarse abrasive. Then finishing is done with fine-grained stones. The engine and machine are securely mounted on a special stand. Cooling and lubricating fluid is continuously supplied to the working area. At the final stage, the treated surface must be washed with soapy water to remove chips and abrasive particles. Diamond hones are almost universally used in professional equipment - they are more economical than ceramic ones.

To reduce wear of parts when running in the piston ring-liner assembly, it is recommended to use the Active Plus engine additive from . This tribological composition is specially designed to create conditions for comfortable operation of the power unit. The composition optimizes the gaps in piston-liner pairs, thereby equalizing compression across the cylinders. Suprotec Active Plus also increases the efficiency of hydraulic compensators by improving the lubrication of operating components. All these factors make it possible to avoid excessive wear of parts during the running-in stage. Also, the Active Plus tribo composition can be used to prevent scuffing on any gasoline engines, including those equipped with turbines. This is cheaper than repairing a worn cylinder-piston group.

Process Features

In repair shops, honing is done in stages, in two main passes and a third – additional. These works differ from the factory procedure, but they are sufficient to stabilize the engine. Honing of cylinders is carried out as follows:

1. The parts are treated with a coarse abrasive stone. This is the primary stage that will prepare the part for final work.
2. The second step is fine-grain abrasive. Precise processing brings the surface to the desired state.
3. Application of abrasive paste. The final step, which eliminates microdefects, smoothes out depressions and corners. The paste makes the hone in the engine cylinders as smooth as possible. The stage is additional, because this is the most subtle processing, designed to improve the result of the main work; car mechanics often do without it.

After completion of the procedure, the cylinders are cleaned to remove metal shavings and polishing residues.

Attention! For processing, different bars with abrasive are used, ceramics and diamond elements are used. Ceramic abrasives are more reliable than diamond abrasives; they last longer, which is why such polishing requires less investment.

Do-it-yourself honing is a difficult job, but doable for an experienced mechanic. In order not to spoil the cylinder, the master must monitor the clarity of the marks and their location. Equipment for performing the procedure yourself is also called a hone - it usually looks like a bottle brush. There are designs made from working elements attached to a rod, but the first option is easier to handle.

In garage conditions, a hone in cylinders is created as follows: the equipment is inserted into a drill chuck, ensuring the accuracy of the work using a level and feed rack. This will eliminate defects during processing. During the application of the hone mesh, the surface and the hone itself are irrigated with lubricant - a mixture of machine oil and kerosene.

Features of honing tools

The honing tool is the head. It contains the adjusting rod 1. By changing its length (tightening or unscrewing the nuts), the position of the abrasive bars is changed.

A double-sided conical adjustable rod 1 is mounted inside the head, through which the radial rods together with the abrasive bars move apart, adjusting the diametrical size and compensating for the wear of the abrasive bars 4. Movement is possible up to 0.5...2.8 mm. As wear occurs, the turning size must be restored, so the machine operator has the opportunity to obtain the desired size without replacing the bars.

Special cylindrical clamps 5 do not allow changing the set size. The processing accuracy corresponds to class 1-2. You can achieve a mirror-like shine of the resulting surface.

The honing head is used with a special machine 3G833. It has a vertical rigid shaft. It allows you to obtain rigid rotation of the tool without signs of runout.

Design of the honing head: 1 – rod for changing the outer diameter of the hone extension; 2 – workpiece; 3 – spindle; 4 – abrasive bars; 5 – cylindrical clamp

External honing is performed on a fixture that can be mounted on lathes. For large machines such as DIP-300 or DIP-400, an external honing head KhNP-150 is used. It allows external polishing of parts with a diameter of up to 150 mm.

External honing head KhNP-150: 1, 2, 7 and 8 – abrasive stones; 3, 6 – locking expansion pads; 4, 5 – brackets for fixation

The part is installed into the machine spindle. A honing device is located on the caliper. The rotating part is in the zone of action of the bars, which grind the surface. The tool is fed longitudinally in different directions.

Honing and repair of Alusil and Nicasil cylinders

Honing a cylinder block made of aluminum alloy has its own characteristics.

• Alusil
  Blocks made using Alusil technology are now officially equipped with repair piston sizes from manufacturers (usually the sizes are +0.5 mm and +1 mm, less often smaller pitches of +0.35 and +0.7 mm are used). Repair-sized pistons, just like standard ones, are coated with a thin layer of iron on top. Engine repairs using uncoated pistons result in rapid “sticking” and jamming of the piston group.

  Repair kits are manufactured specifically for the technology of boring aluminum blocks. Failure to comply with the technology results in rapid failure of the repaired engine.

  Boring is performed with standard cutters, which are used on cast iron blocks. The main difference lies in the honing process. Special abrasive bars with an “anti-sagging” surface should be used. They remain clean throughout the entire operation. Otherwise, the particles of aluminum remaining on the honbrusk, when heated, set on the surface of the cylinder, and scuffing will instantly form.

  The world's largest manufacturer of tools, Sunnen, which also produces honing stones, recommends using equipment based on abrasive particles of silicon carbide (SiC) when honing cylinder blocks made of aluminum alloys.

  Three types of bars are consistently used. The first block of type C30-J55 removes the worn layer with an allowance of 0.04–0.08 mm after boring. The second type C30-J84 performs honing and increases the repair size by 0.01-0.02 mm, and also removes defects from the previous operation. The third type C30-C03-81 carries out finishing grinding without changing the repair size.

  After boring the aluminum block, you must thoroughly rinse it from chips. Even minor contamination causes aluminum to stick to the cylinder walls and the abrasive tool. Scoring and tearing out of abrasive particles occur.

  Honing is carried out when three conditions are met. First, thorough filtration of the coolant and lubricant. Secondly, moderate pressure of the abrasive bars against the wall of the block. Thirdly, an exact match between the diameters of the bar and the piston. Violation of these conditions leads to overheating of the treated surface and tearing of abrasive grains from the bar. All this is accompanied by the formation of scoring and deterioration in the quality of processing. If you do not set up the process in time, you can irrevocably ruin the entire work.

  Honing the cylinder block allows you to achieve the optimal size and precise gap between the rubbing parts (from 0.01 to 0.02 mm). However, the work surface does not yet meet the roughness requirements, so it needs to be smoothed using a finishing treatment.

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  Polishing during engine overhaul serves as an alternative to chemical etching used in production conditions. As a result of polishing, a very small layer of aluminum (about 1 micron) is removed and silicon crystals are exposed. For this purpose, soft felt shoes C30-F85 are used, fixed in the honing head, and a soft silicone paste based on AN-30 silicone, which does not affect silicon inclusions, but removes the excess layer of aluminum.

  After polishing with silicon paste, the surface becomes a characteristic dark gray color, and there should be no traces of a hone or other cutting tool on it. Its structure contains silicon grains, and the main layer of aluminum alloy, which is a binder, is 1-2 microns deeper. Due to randomly scattered silicon inclusions, the structure becomes porous. Due to this, the oil is retained in micropores during engine operation and creates a film that envelops the rubbing parts.

  The German company Gehring offers another technology for processing cylinders made of aluminum alloys. The main difference is present at the roughing stage. Thus, instead of the first SiC-based abrasive stone, diamond-coated stones are used at the first processing step, and then at the final honing stage and at the final polishing stage, honing stones and silicone carbide-based polishing paste are used.

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  The proposed boring and honing technologies are used both for blocks based on aluminum alloys Alusil (Silumal), and for more advanced versions of Lokasil and Silitec (silicon sleeve filled with an aluminum alloy consisting of 25% silicon compounds). In any case, the geometry and microstructure of the cylinders does not differ from the factory one.

  If scuffs or other defects in the cylinders exceed the repair dimensions in depth (up to 0.7 mm or in some blocks up to 1 mm), then such repairs cannot be made using boring and honing. Here you need to use replaceable sleeves. Similar parts are supplied for some types of blocks in the form of spare parts.

  Replacement liners are made of a material homogeneous in composition with the cylinder alloy. This is usually aluminum containing up to 17% silicon compounds. Replacing aluminum sleeves, as a rule, is no different from replacing cast iron analogues. The main difference between aluminum is its higher thermal conductivity.

  Rules of thumb for replacing liners require that the liners be cooled vigorously (e.g., in liquid nitrogen or in a deep freezer) and that the cylinder block be heated vigorously. The sleeve must be inserted quickly so that it does not have time to heat up even from simple manual effort without the use of a press or impact tools.

  A characteristic feature of the aluminum sleeve is the impossibility of adjustment in the event of an inaccurate fit in the block. A cast iron sleeve can be pressed in, but an aluminum sleeve in this situation begins to deform. It can only be removed by boring on a lathe. This actually means that you need to buy a new sleeve and usually wait several days for your order.

  After installation, the liners are bored and honed using the technology described above. Pay special attention to the protrusion of the sleeves above the mating surface of the block - it is not recommended to trim it when boring the sleeves. Otherwise, the protrusion of the pistons at top dead center may exceed a maximum value of about 0.5–0.7 mm. There may also be a difference in height between the plane and the top of the front cover of the unit.

• Nicasil
  Nicasil aluminum alloy has high strength and wear resistance, but there still comes a time when it becomes unusable. Is it possible to overhaul such a unit? Let us consider the characteristic features of this alloy in order to understand whether it is worth reducing it.

  Given their excellent wear resistance compared to other aluminum alloys, these blocks require repairs less often. Based on this, most car factories do not produce repair pistons for these engines. Only owners of some BMW models can count on repair pistons and rings increased by 0.07-0.08 mm. If you are lucky and you find repair parts, and the surface of the cylinders has not yet worn out to a critical depth, you can try to do something.

  Classic boring of Nicasil blocks is even theoretically impossible, because not a single cutter will take a silicon carbide alloy. And besides, considering the repair dimensions of the pistons are less than +0.1 mm, it is quite possible to get by with honing the cylinder block.

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  When processing such blocks, there are pitfalls. Not all honing stones are suitable. You can use either diamond or boron nitride based ones. Honing of the cylinder block is carried out with minimal pressure to ensure the integrity of the coating and not push it through in the thinnest places.

  In general, the procedure requires maximum care and the highest qualifications of the master. But even in this case, success is not guaranteed. The ellipse of the block can become critical even with a deviation of 0.03–0.05 mm. The minimum force of the bar does not completely eliminate the incorrect geometry, and increasing the force can lead to chipping in a thin place of the ellipse. Therefore, it is not possible to return the block to ideal geometry in all cylinders.

  A damaged coating (including that obtained during the honing process of the cylinder block) can be a death sentence for replacing the part. Manufacturers usually do not regulate the repair of such defects. There are stories among auto mechanics about the possibility of re-coating the surface of the cylinders with Nikasil. Long practice shows that repeating production technology is expensive and impractical. Therefore, in most cases, honing cannot be carried out.

  If the working surface of a block made using Nicasil technology is damaged, there are several options for solving the problem.

  The most radical way is to replace the cylinder block or engine assembly. This option is suitable for a new car under warranty, but for a ten-year-old car the cost of the motor may exceed its own price.

  Europe is full of auto wrecking yards where you can get a used engine. This is a cheap option. But in our country this market is still underdeveloped. In addition, in addition to buying a motor, you will have to fuss with documents and registration.

  A “folk” way to line an aluminum motor with cast iron liners.

  Manufacturers categorically do not recommend such a replacement. But if you don’t listen to them and have sufficient qualifications, then it is quite possible to carry out such a sleeve. There is already quite a lot of experience and developed technologies for using cast iron liners in blocks made of aluminum alloys.

  Blocks made using Nicasil technology are quite suitable in terms of their characteristics, since the strength and roughness of cast iron and Nicasil surfaces are similar, and the pistons slide equally well in both cases. Nuances are possible on older engines that use rings without chrome coating. Such rings require more frequent replacement due to their accelerated wear.

equipment requirements

The application of hone to the cylinder is carried out using a special metalworking unit - a honing machine. It consists of a surface on which the workpiece is fixed, a control unit, and a drive. Characteristics by which equipment is distinguished:

1. Spindle location. The hone is held by a spindle; depending on its location, the machine is considered vertical or horizontal, and for specialized honing, an inclined machine is used.
2. Number of spindles. To process complex, multi-level parts, multi-spindle machines are used to make working with objects easier. Honing of simple elements is carried out on equipment with one spindle.
3. Availability of an automation system. The machine can be automated to make it easier for the technician to work with complex parts.

Program control controls the processing, ensures the stability of grinding, calculates the exact amount of oil for irrigation, and is responsible for calculating the cleanliness of polishing.

The main advantages of honing.

When compared with other methods of treating cylinder block surfaces, such as polishing and lapping, the most effective and accurate method is turning (honing). Thanks to it, the least wear of parts is ensured, the maximum pressure in the cylinders increases, which leads to an increase in engine efficiency and extends its service life.

Thanks to turning, an inconspicuous mesh is formed on the surface of the cylinders. Thanks to it, the oil remains on the walls for a long time. The contacting parts of the engine are constantly lubricated, improving the functioning of the engine as a whole.

For honing cylinders, professionals advise using diamond stones, although their initial price is higher than the cost of ceramic abrasives. Most companies use this method of finishing cylinders. Less wear on diamond abrasives offsets their cost. Thanks to the use of diamond heads, the hole can be given an ideal geometry. In the process of restoring cylinders by honing, it is possible to obtain straight walls and a round shape, the correct quantity and quality of hatching. And this is the main guarantee of the longevity of the engine and the car as a whole.

Honing for internal combustion engine parts

When repairing an engine, as was said earlier, most of the internal cylindrical surfaces - holes - are honed. These are the bushings of the upper connecting rod head, the holes of the lower connecting rod head, the rocker arm bushings of the valve mechanism drive, the crankshaft beds and, of course, the engine cylinders.

If we consider that cylinders are the heart of the engine, then knowledge about honing, the properties of the resulting surface and methods for obtaining it is cardiology.

For normal operation of piston rings (everyone can come up with a cardiac analogue for themselves), it is necessary to provide a certain surface microprofile on the cylinder wall - a set of intersecting marks. The depth and relative position of these scratches largely determines such operational parameters as compression, power, oil consumption, fuel consumption, wear of the cylinder-piston group and engine life. The application of these marks occurs precisely during the operation of the honing head with bars installed in it along the surface of the cylinder. The simultaneous rotation of the tool and its reciprocating movements (this is not for you to go back and forth with a drum machine:) determines the angle of mutual intersection of the marks on the surface of the cylinder - the honing angle. The type of abrasive used, its grain size and bond determines the roughness of the cylinder surface, the depth and size of the marks. Accordingly, it is not difficult to guess that it is necessary to distinguish between rough and fine honing, and therefore the stones used for honing. The “trend setter” in this matter, the company KOLBENSCHMIDT (KS), gives clear recommendations for performing this operation. Therefore, I decided not to take a moment in the workshop to film the honing process and did not even go to the warehouse to get the whetstones. I just scanned the pictures from the KS booklet. So, the recommendations apply to the use of abrasives and lubricants, equipment setup, processing allowances and, most importantly, methods for quality control of the work performed. To control roughness, the Germans use a Hommel tester with the ability to print a microprofile diagram and roughness parameters in evaluation units. To control the honing angle, a special template film is used. In the photo it is attached to the cylinder wall.

Advantages of Honing

Although grinding, polishing and lapping are considered the most popular and common methods for machining cylinders, in most cases honing is preferred as it is more efficient and accurate. In addition, when honing you can encounter other advantages, including:

Increased wear resistance. This, in turn, has a positive effect on the further operation of the engine and allows you to maximize its service life. Lack of marriage details. The fact is that when processing cylinders with a hone, the surface is subjected to less pressure than, for example, when grinding. That is, the chances of receiving a marriage top hat are significantly reduced. Achieving technical requirements. Due to the fact that honing stones have a wider range in comparison with the same abrasive wheels, achieving the technical requirements for the part is several times easier. Making a precise hole. Due to its design, during processing, the hone can automatically correct deviations of the hole from the permissible values ​​that remain from previous operations, for example, after drilling. Reducing the time allotted for processing. As you know, there is more than one device for honing cylinders. There are also devices that allow you to hone a block of parts. Due to the processing of several holes simultaneously, the time allotted for the operation is reduced

This is especially important in mass production, where thousands of cylinders must be produced per day.

Processing tool

For processing, a special honing tool is used - honing. Honing heads are classified according to the following characteristics:

• 
  according to the method of fastening the abrasive tool: rigid;

• floating;

• according to the method of ensuring size: adjustable;

The honing head consists of:

1. housings;
2. abrasive bars;
3. rod;
4. control coupling.

The body has milled grooves into which abrasive stones are installed. A collet mechanism is provided inside the body, ensuring simultaneous and smooth ejection of the bars.

Abrasive stones are made from sintered composites or matrix diamond elements. The grain size does not exceed several tens of microns.

The coaxiality of the motor sleeve and the tool is ensured by the rod. The resulting hole diameter is adjusted using a coupling.

Self-unclosing hones are made in the form of a brush that used to be used to wash milk bottles. Small abrasive stones are attached to the ends of the spring legs. This device is intended for use in conjunction with a hand-held electric drill or screwdriver.

Processing with such a head is close to fine grinding or polishing. The absence of rigid fastening does not allow the correction of surface defects after boring, but reduces the roughness to a value of Ra 0.25.

What is cylinder block honing?

Engine hone is the result of processing, the “correct roughness” that helps retain engine oil on the elements. It represents shallow risks running in a grid across the surface. Their depth does not exceed 0.05 mm. The hone in the engine ensures sealing of the liner and piston, reducing equipment wear. The protective effect is what the operation is for. But it works when the hone mesh is applied without defects: the network parts are located with a consistent frequency, evenly, without errors in direction.

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Replacing the piston and boring the cylinder

If such a situation occurs, then replacing the piston alone does not solve this problem.
It needs to be solved comprehensively, i.e. replacing a piston plus boring a motorcycle cylinder. Those. cylinders must be bored every time their wear has been detected. It is also worth considering that not all cylinders are subject to wear, even after quite a long period of operation in very difficult conditions. There are also cases where a vehicle lives out its life without ever boring the cylinders. Parameters for determining cylinder wear:

• if at the top dead center of the cylinder its dimensions have changed by 0.05 mm from the original ones;
• if in the place where the piston skirt and the cylinder wall come into contact, the size has changed by 0.03 mm.

Thus, the two indicated parameters may well answer the question of whether or not it is worth boring the cylinder. If there is at least one of the changes listed above, then the answer is obvious - boring is necessary.

There are also worse situations when a so-called “stepped” defect appears in the upper part of the cylinder. The resulting step reduces the wear time of the cylinder, piston rings, and ring seats on the piston, resulting in very noticeable shocks during driving. However, this defect becomes noticeable without any measurements. When it changes, the nature of the engine's operation changes - it begins to vibrate strongly.

This is a direct indication for immediate repair, since the ellipsoidality accompanying this defect leads to the fact that the piston rings adhere worse to the cylinder walls. This, in turn, can lead to breakthrough of gases from the cylinder into the crankcase, disruption of compression in the engine, which also increases oil and fuel consumption.

In this case, boring the cylinders will help restore the necessary parameters of this part of the engine. However, by boring we mean not only the restoration of the geometric parameters of the motorcycle cylinders, but the restoration of the normal position of the mating parts relative to each other. In other words, if you only correct the geometry of the cylinder, it will not be enough to restore normal alignment and the normal location of all the main surfaces.

The consequence of this is the appearance of excess friction, which affects other structural components of the piston group. In other words, all moving parts that participate in the operation of the engine and are part of the piston group will be subject to additional bending, compression, etc. loads. This, in turn, can cause further breakage of the cylinders as the engine operates.

However, nowadays there are still masters who want to carry out this process on their own. Perhaps some people don't have enough money, while others just like to spend time in the garage, tinkering with their motorcycle. In any case, it is possible to bore a motorcycle cylinder yourself. It is worth noting right away that the boring method is also suitable for an automobile cylinder block. The only caveat is that turning to a turner is inevitable, since it is the turner who can make the appropriate mandrel that is suitable for this process.

The mandrel should have dimensions depending on the size of the cylinder being bored. For example, if the diameter of the cylinder is 76 mm, then the diameter of the mandrel should be 74 mm, and its length should exceed the length of the cylinder by approximately 150 mm, although a little more is possible. After the mandrel is ready, you need to make a hole in it into which the knob will be inserted, and use a hacksaw to cut a groove along the groove, the depth of which should be approximately 10 mm.

Sleeve engines

Power units with removable sleeves are somewhat more difficult to process using a hone, since it is problematic to mount them vertically on the machine.

Suppliers of finished cartridges claim that their product has successfully undergone the honing process and does not require any additional processing. It is undesirable to believe this, because if it turns out that the treatment was not carried out, the power unit will not be able to fully operate and will quickly fail. To avoid this, it is recommended to hone even new liners.

The plate is attached to the block after installing the liners and is clamped, like a full-fledged cylinder head, in strict sequence and in compliance with the tightening torques. After which hone treatment is carried out, as in the case of a linerless cylinder block.

The use of a simulating plate allows minimizing non-compliance with dimensions. Honing in this case can be divided into four stages:

Rough processing. This process involves removing most of the metal. It can replace the boring process. To carry it out, you will need a lot of lubricating and cooling fluid, as well as diamond hones.

Finished with 150 grit hone.

Hone treatment with 300-500 grit.

Some motorists are confident that honing can be done at home themselves, using only a drill or hammer drill. This is an erroneous misconception, since it is unlikely that it will be possible to ensure the necessary accuracy and roughness at home - cylinders treated in this way will not be able to work for a long time, which will lead to rapid engine failure.

Main purpose of honing

The purpose of this operation is as follows. The micropattern creates a slight roughness on the cylinder mirror. It is needed so that the lubricant lingers on the surface.

Everyone knows that oil in the cylinder-piston mechanism is needed to reduce friction between the rings and cylinder walls, as well as to ensure the necessary cooling of parts when thermal loads occur.

In a power unit that has exhausted its service life, the geometry of the cylinders changes, which reduces engine performance. Over time, the inside of the cylinders becomes scuffed and roughened, which differs from the original parameters made at the factory.

This damage can be eliminated by boring the cylinders. If a similar procedure has already been carried out, then the size of the cylinder will no longer correspond to the first, but to the second repair value. After the operation has been completed, you need to make the appropriate notches using a hone.

In addition to improving cylinder surface lubrication, honing has another purpose. This procedure eliminates barrel or cone shapes that were created during the diameter enlargement process.

Honing the motor ensures maximum roughness precision, which is more difficult to achieve with polishing or lapping. In order for the internal combustion engine to have the required performance after such a repair, the size of the cells and the depth of the notches must correspond to factory standards. We’ll talk about how the procedure is performed correctly, as well as the standards, a little later.

What is honing

What exactly is cylinder honing or boring? As we have already mentioned, this is a very important stage in repairing the engine, since it serves as the final stage in major work on the car’s power plant. Boring is used to process not only the parts we have already listed, but also bushings, connecting rods, crankshaft beds and, moreover, it is applied to planes. Now let’s look at the most important question: why carry out this procedure, and what benefit will your iron horse get from it?

When is honing needed?

It is impossible to say exactly when the engine will need boring and honing of the cylinder block - everything is very individual. The degree of wear depends on a number of factors: the quality of gasoline and engine oil, driving style, operation of the cooling system and other parameters. As a rule, such repairs are required for engines with a mileage of 100,000 km or more.

Professional car mechanics can accurately determine when scuffing appears and the engine requires honing. If you notice any of the following signs, then you need to show the car to a specialist:

Blue smoke occurs when the piston ring cannot completely collect oil from the surface of the cylinder, and it burns along with the gasoline. This is a consequence of the changed geometry of the internal channel along which the piston moves. Lubricant consumption increases for the same reason.

Dips at idle and loss of power are also caused by a violation of the geometry of the worn cylinder. The piston rings no longer fit so tightly to the cylinder walls of the block; microscopic gaps appear through which gases break into the crankcase. Compression drops in the combustion chamber, which causes a drop in power.

Combustion products slipping past the piston do not perform useful work, they simply fly into the crankcase. With the same operation, such an engine consumes more fuel than a fully functional unit. Hence the increased fuel consumption.

Important Requirements

When checking the dimensions of the cylinders, ensure compliance with the following parameters:

• Barrel-shaped, corseted and tapered. These terms refer to the difference in diameters in different parts of the cylinder or liner.
• Ellipsity, which refers to the difference in the diameters of a circle at different points.

Such defects appear as a result of careless work on a boring machine or during operation of the power unit.

A separate problem is achieving the required roughness parameters. The surface should not be mirror. There should be small notches left on it, resulting from the passage of the hon. These notches are necessary so that engine oil lingers . This helps improve lubrication of piston group parts. Later, during running-in, the sulfur contained in the lubricant will create a sulfide film on the surface of the cylinder, which reduces wear of parts, since its parameters are much harder than metal.

Why do you need engine honing?

Any part does not last long. Each one, at one time, requires repairs, but a resourceful driver knows that there are methods and approaches that will extend the life of the part and save money. Honing the cylinder block is one such way out of the situation. As for the engine parts themselves, they change in parameters during their service. What's even less pleasant is the appearance of scratches everywhere.

As you well understand, all this has a very detrimental effect on the operation of the engine as a whole, and this is what it leads to worsening:

Therefore, it is worthwhile to immediately begin repair work on the unit, so that in the future you do not have to replace the crank mechanism, but here we are talking about a completely different amount. It can also be noted that during processing you can put old pistons on updated liners if they are still in good condition.

Now let's talk about processing technology. The work itself is done by the instrument from which the name of the operation comes, namely the hon. It moves over surfaces with rotational movements, cutting off layers of metal of very small sizes. Workers use cutting fluid to glide. Often this is the kerosene we all know, but other options based on water-oil emulsions are also allowed. The main thing is to correctly calculate the pressure in order to achieve a uniform and correct surface of the cylinder.