Long and trouble-free operation of the car enginedepends entirely on its technical condition. Unfortunately, there are no perpetual motion machines, and over time moving parts inexorably collapse. One of the most loaded parts of an internal combustion engine are the valves in the cylinder head. They let the fuel mixture inside the cylinder and at the same time, for the duration of the working cycle, become part of the walls of the combustion chamber, taking on all the destructive effects. Therefore, valve repair is an inevitable stage in the operation of any engine. To properly perform this work requires special tools. In particular, it is a set of cutters for valve seats. But in order to understand why they are really necessary, one should delve a little bit into theory.
Gas distribution device
As already mentioned, the valves let in andrelease the fuel mixture into the combustion chambers of the cylinders. Since during the working cycle the pressure of the mixture acts on the plate, the edge of the plate is cut under the cone. The combustion chamber window also has a chamfer corresponding to this cone. The seat of the valve disc to the edge of the window is called a saddle. The quality of the part will adjoin to the surface depends on the set of performance indicators of the engine's working process, including the most important one - compression.
The tighter will fit the valve to his seatwhen closed, the greater tightness in the cylinder will be achieved. Consequently, the required operating power will be maintained when the engine is running.
The need for special tools for repair
Valve seats after big run inevitablywear out. Chamfer on the surface of the saddle over time becomes more cylindrical. The window itself is made oval due to uneven wear. A violation of the geometry may also appear due to overheating of the engine, when the head of the block becomes deformed and its geometrical parameters change. Shells also appear on the surface of the valve seat, directly on the chamfer itself.
Such defects lead to leakage of the chamber.Combustion and destructive effect on its edge. Therefore, during engine overhaul, the cylinder head is subject to mandatory verification. The mechanisms are lapped to their seats with the help of a special tool, in particular, cones for repairing valve seats. Without them, not a single overhaul of the engine.
Indications for the use of special tools
The use of a roller cutter for valve seats is necessary in the following cases:
- damage to the working surface of the seats, which can be restored;
- after lapping valves on the glasses;
- after replacing valves, bushings or seats;
- when conducting a comprehensive repair of the engine.
In all cases, repair with the help of sharoshek is possible in the garage conditions, of course, with possession of the skills of assembly and disassembly of the engine. All work is done on the removed cylinder head.
Tool characteristic
Sharco for valve seats - prettya simple device that performs its functions very well. Externally, the part is a cone-shaped nozzle with a through hole. On the side there are fasteners for special cutters.
When installing a roller cutter for valve seatsrotates the chamfer layer. Details attached perfectly rounded shape. Cutters in a single form does not happen - it is always a set of cones of different angles. The angle ranges from 15 to 60 degrees, since the chamfers of the saddles on different motors are different. Also processing is carried out in several stages, with a gradual increase in the angle. For quality work, there must be a horizontal guide. What is it for? The horizontal guide ensures coaxiality and even processing of the seat around the entire circumference.
Features tools brand Neway
Neway valve cutter mounts are one of the mostpopular tools for grinding valves and milling saddles. A feature of this tool are special cutters. Using them to repair valve seats is especially easy, without the use of special physical strength.
This tool is completely manual.Another distinctive feature are quick-release pilots. These are fixtures installed in the valve guides. Thanks to precision machining of parts, high milling accuracy is achieved. As a result, no subsequent grinding in of the valves is required. You can immediately start operating the engine, without running.
The cost of the tool for grinding
A set of cutters for valve seats includesa set of cones of different diameter and angle, interchangeable cutters and a vertical guide. With the help of the latter, the coaxiality of the working surface is established. A semi-professional set of 6-10 elements of domestic production has a cost of 1-3 thousand rubles. Professional tools, consisting of 13-15 items, cost about 10-15 thousand rubles.
Ввиду высокой цены, такая шарошка для седел Valves are used only in car services. Practically all kits are universal and allow milling saddles and lapping on almost any car. There are also kits designed for specific brands. For example, it is a cone for valve seats VAZ. Suitable for classic carburetor models, as well as for more modern injection models.
Types of repair saddles and lapping valves
Restoration of elements with the help of roller conesperformed by milling and grinding, followed by grinding. When milling cones are used with different diameters and angles. The most common is the angle of 45 degrees. According to this scheme, most of the valve seats in the cylinder heads, including domestic cars. Cutters with a large angle are used to align the chamfer and give it the desired width.
Due to the fact that not always during the repairthe exact values of the chamfer angle of the saddles are known; the default running cones with angles from 30 to 60 degrees are used by default. Cutters are available in two options - for "solid" metal heads and for machining saddles made from softer metal.
Countersinks
When repairing it is possible to use a roller cutterfor valve seats. Their difference from cutters is to install a non-removable (and sometimes adjustable) cutter. The advantage of such devices is that they can form the entire working surface of the saddle at once.
Another difference is the other way to install the support. One support is installed on the valve sleeve, the second - on the bracket. This greatly increases the accuracy of the working surface.
Valve seat repair
Before the procedure of processing the saddle is desirablereplace or at least repair valve bushing. The guide of sharoshka will lean on it. After that, processing with cones (cones) takes place - from small angles to large angles, if specific valve seats allow this. Processing takes place to increase the width of the chamfer to 2 mm for the intake valves and 2.5 mm for the exhaust. After that, the working surface is polished to remove any burrs. On this directly milling saddles finished.
Mandatory final procedure - lappingvalves. It allows you to check how accurately the milling works. To perform lapping using a special abrasive paste with fine grain. Diamond pastes are not recommended due to the hard particles they contain. They can further accelerate the wear of the saddles. The lapping is performed by rotational movements of the valve on the seat. At the same time, the valve is periodically raised and lowered in order for the extruded paste to re-enter the working surface of the seat. If after 1-2 minutes the surface did not get used, it means that the milling is unsatisfactory. Re-processing is required.
Conclusion
Milling valve seats and their lapping -The work is simple, but requires high accuracy. Also for this repair requires special tools, which is a cone for valve seats. If such an operation is performed infrequently, it would be wiser to turn to a car-care center.
