Cold welding welding

Because of a disruption in the integrity of the cone, the plug or o-ring is not able to seal the cylinder tightly. The restoration of the thread can be carried out in several ways, including without removing the cylinder head from the engine .

Maintenance operations of the machine are in most cases carried out with unscrewing and tightening the threaded fasteners. If parts such as a stud, nut and bolt are damaged, they are replaced with new ones. But repair becomes more appropriate when the thread in the housing element is damaged.

The details of fastening the spark plugs are not, but they have a connecting thread, which is damaged in the following cases:

• In case of dust and dirt. To prevent this, in engines with a well it will be useful to turn the spark plug a few turns before removal and remove dirt with a brush or air purge.
• Work with a candlestick that does not provide proper fixation and subsequently leads to skew.
• Tightening with exceeding the permissible force, the exact value of which can be found in the operating instructions.

The restoration of the thread is carried out by various methods, which have their own nuances. For each case, the most optimal one is chosen depending on the price, labor, technological equipment and design. Each type of repair implies compliance with the size tolerance and the provision of the ratio of the holes.

In order to realize the restoration of the thread in the block, the rational installation of the insert of a self-tapping or spiral type, with the presence of a fixing belt, and also the opening of the hole. The insert should not touch the combustion chamber. At the end of the installation, it is calibrated with a tap to eliminate damage caused during installation.

What is cold welding

It is a way of building and combining metal elements, without the influence of high temperatures. In this case, the surfaces are not welded, but are glued together. The cold welding mass begins to deform, then penetrates into the parts used for work. Here there is no mutual penetration of substances into each other, the appearance of interatomic bonds, but a dense bond arises. In this case, this method helps to restore the spark plug thread, recreate the lost elements and repair damage.

Carrying out work

Today you can find in stores a large list of goods of foreign and Russian production. It is worth noting two main types: plasticine and liquid. The latter have two components, consisting of the main mass used in the pasting, and a hardener. Plasticine means consist of a bar with one or several layers, before which mixing is necessary. In order to carry out the restoration of the internal thread by cold welding, it is desirable to purchase a two-component agent, which is realized in two bottles.

It requires preliminary degreasing of all surfaces and anti-adherence treatment both outside and inside, since the presence of plaque and fine particles can worsen the result. Then the components from the two vials are mixed on a plastic or wooden surface. Apply the resulting mass to the thread, which is screwed inward and left to dry completely. If the temperature is respected, the restoration of the thread will be completed after the time specified in the instructions.

Repair with conventional welding

The cylinder head is removed from the engine and the damaged area of the candle is fused by welding. On the milling or boring machine, the groove under the candle is machined, and the bogie surfaces are restored. The new hole is drilled at a fixed angle, and the thread is cut. Crimping the head is the final stage, it is a leak test in a water bath with high air pressure.

It should be noted that in the field of welding too much heat can contribute to the appearance of cracks. Therefore, the fusion of metal is used in extreme cases, when it is impossible to use other methods.

Thread restoration with insert flange

The head of the unit is installed on the milling or boring machine. Broken thread is drilled and a new one is cut to use the repair insert. It is produced on a lathe, most often of bronze. Inside there must be a thread with the required dimension. To perform the heat removal function, the insert must be in close contact with the walls, for this purpose the diameter of the external thread is made more than the nominal. It is wrapped in the head after applying bakelite varnish. The part is fixed by flaring the edge of the insert.

Manual restoration

Restoring the torn threads manually, without removing the head of the blocks from the engine, is unable to properly correlate the old and new holes, which can damage the part. It is also difficult to prevent the ingress of chips and tightly fix the insert, avoiding twisting together with the candle.

Spiral insert

This method is mainly used on the removed block, but at a suitable depth of the well, location and size, it is possible to avoid parsing the engine. Before starting the restoration of the internal thread, you need to check the arrangement of the valves and the piston to provide a place for screwing the tool.

A hole is made for a candle with a tap of a combined type, which makes it possible to work without a metal-cutting machine. When the head is on the engine, a plastic grease is placed in the grooves in order to hold the chips.

The tap during the twisting in the broken hole for the candle is centered and cuts the thread without distortion. The support flange of the insert contributes to the non-standard arrangement of the candle, and this method is not suitable for heads having a conical seal due to the small diameter of the wells.

Insert with fastening belt

After forming the part, the external and internal threads are cut in such a way that no overlapping of the cavities and projections of the profile occurs, which allows achieving the required strength of the element. With the help of the installation device, the insert is wrapped in candle wells with great depth and easily removed from the outside. Heat-resistant glue will help in ensuring tightness. On the two outer wraps of the insert there must be a knurling for tight fixation after flaring with the help of a special profile.