Cutting tool for car valve seats

The long and trouble-free operation of the engine of a car depends entirely on its technical condition. Unfortunately, there are no perpetual motion machines, and moving parts inexorably collapse over time. One of the most loaded parts of the internal combustion engine are the valves in the cylinder head. They let the fuel mixture into 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, repair of valves is an unavoidable stage in the operation of any engine. To properly perform this work, special tools are required. In particular, this is a set of cutters for valve seats. But in order to understand why they are really necessary, it is necessary to go a little deeper into the theory.

The device газораспределительного the mechanism

As already mentioned, the valves let in and release the fuel mixture into the combustion chambers of the cylinders. Since during the working cycle, the compression force of the mixture acts on the plate, the edge of the plate is tapered. The combustion chamber window also has a chamfer corresponding to this cone. The place where the valve plate adjoins the edge of the window is called the saddle. On how much the quality of the part will fit to the surface, depends on the many operational parameters of the engine working process, including the most important - compression.

The more tightly the valve will fit against its seat in the closed state, the greater the tightness in the cylinder will be achieved. Consequently, the required operating power will be maintained while the engine is running.

The need for a special tool for repair

Saddles valves after a large run inevitably wear out. The chamfer on the surface of the saddle becomes more cylindrical with time. The window itself becomes oval because of uneven wear. A violation of geometry may also result from overheating of the engine, when the head of the block warps and its geometric parameters change. Also there are shells on the surface of the valve seat, directly on the chamfer.

Such defects lead to a leaking combustion chamber and destructively affect its edge. Therefore, when carrying out engine overhauls, the cylinder head must be checked . Mechanisms are grinded to their seats using a special tool, in particular, cutters for repairing valve seats. Without them, no major overhaul of ICE is carried out.

Indications for use of the special tool

Use of the cutter for valve seats is necessary in the following cases:

• Damage to the working surface of the saddles, which can be restored;
• After grinding the valves on the glasses;
• After replacing valves, guide bushings or saddles;
• When performing complex engine repairs.

In all cases, repair with roller cutters is possible and in garage conditions, of course, with the skills of assembly and disassembly of the engine. All work is carried out on the removed head of the block of cylinders.

Characteristics of the instrument

The cutter for valve seats is a fairly straightforward device that performs its functions very well. Outwardly, the part is a cone-shaped nozzle with a through hole. On the lateral surface there are fastenings for special incisors.

When they are installed, the cutter for valve seats rotates the chamfer layer by rotating movements. Details are given an ideally rounded shape. Single cutters do not happen - it's always a set of cones of different angles. The angle is from 15 to 60 degrees, because the chamfers of the seats on different motors are different. Also, the treatment is carried out in several stages, with a gradual increase in the angle. For a good work, there must be a horizontal guide. What is it for? The horizontal guide ensures alignment and smooth handling of the seat along the entire circumference.

Features of Neway tools

Cutting tools for valve seats Neway - one of the most popular tools for grinding the valves and milling saddles. A special feature of this tool is special cutters. With their help, repairs of valve seats are especially easy, without the use of special physical strength.

This tool is completely manual. Another distinguishing feature is the quick-clamping pilots. These devices are installed in the valve guide sleeves. Due to precision machining of parts, high accuracy of milling is achieved. As a result, there is no need for subsequent lapping of the valves. You can immediately begin to operate the engine, without breaking.

The cost of the lapping tool

A set of cutters for valve seats includes a set of cones of various diameters and angles, interchangeable incisors and a vertical guide. With the help of the latter, the alignment of the working surface is established. Semiprofessional 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.

In view of the high price, such a cutter for valve seats is used only in car-care centers. Virtually all sets are universal and allow you to milling the saddles and grinding on almost any car. There are also kits designed for specific brands. For example, it is cutters for valve seats VAZ. Suitable for both classic carburetor models, and for more modern, injector.

Kinds of repair of saddles and lapping of valves

Restoration of elements with the help of cutters is carried out by milling and grinding with subsequent grinding. When milling, cones with different diameters and angles are used. The most common angle is 45 degrees. According to this scheme, most valve seats in the cylinder heads, including domestic cars, are made. Cutters with a large angle are used to smooth the chamfer and give it the necessary width.

In view of the fact that the exact values of the bevel angle of the saddles are not always known during the repair, the most common cones with angles of 30 to 60 degrees are used by default. Mills are possible in two versions - for "hard" metal heads and for processing saddles made of softer metal.

Countersinks

When repairing, you can also use sinker cutters for valve seats. Their difference from the mills lies in the installation of a non-removable (and sometimes adjustable) cutter. The advantage of such devices is that they can form the entire working surface of the saddle immediately.

Another difference is in another way of installing the support. One support is installed on the valve bushing, the second - on the bracket. This greatly increases the accuracy of the working surface treatment.

Repair of valve seats

Before the procedure for the treatment of the saddle, it is desirable to replace or at least repair the valve guide sleeve. The guide roller will rest on it. After that, the treatment is carried out by cones (small cutters) - from small angles to large ones, if specific valve seats allow this. Machining takes place before the chamfer width increases to 2 mm for the inlet valves and 2.5 mm for the exhaust valves. After that, the working surface is ground before removing any burrs. On this, the milling of the saddles is finished.

Mandatory final procedure - lapping valves. It allows you to check how accurately the milling has gone. To perform the grinding, a special abrasive paste with fine grain is used. Diamond pastes are not recommended because of the solid particles contained in them. They can further accelerate the wear of the seats. Lapping occurs by rotational movements of the valve along the saddle. At the same time, the valve is periodically raised and lowered so that the extruded paste re-enters the working surface of the saddle. If after 1-2 minutes the surface does not get stuck, it means that the milling is unsatisfactory. Re-processing is required.

Conclusion

Milling of valve seats and their lapping - the work is simple, but requires high accuracy. Also for such repairs, a special tool is required, which is a roller cutter for valve seats. If such an operation is not carried out often, it will be more reasonable to contact the car service center.