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General requirements for car repair

The main part of mechanical malfunctions of knots and units in operation is caused by friction processes, deformation elements, the aging of the parts, etc. These and other processes entail wear and damaged parts. How to wear can be divided into three periods: the running-in, normal wear and alert. In the process of running an intensive wear of friction parts, resulting in unevenness of the mating surfaces are reduced, increasing the contact area, the specific load is reduced, the wear rate is slowed down and returns to normal wear and tear. The period of normal wear and tear is characterized by relatively low growth rate of the gap in conjugation, but by a certain gap wear rate increases sharply, indicating the start of an emergency wear. Operating the machine with emergency wear leads to breakdowns, which can not be recovered. In operation, it is important to expose the node before the emergency repair wear and tear, while maintenance costs are considerably lower than in the repair of the unit with emergency wear.

Before deciding to repair it is necessary to diagnose the state of the interface units. Generally, diagnosis is carried out by circumstantial evidence, such as increased noise, vibration, oil consumption, a breakthrough crankcase gases and others. For better diagnostics unit must be disassembled, parts washed, inspected and subjected to precise measurements. As a result of the inspection and precise measurements of the decision to continue operation without repair or making repairs. It should be guided by the following considerations: if the actual dimensions of parts are within tolerance zones resolved this guide, the continued operation of the unit without repair possible; if the size exceeded the permissible tolerances, the necessary repairs. Extensions of fields tolerances given in this guide should be understood as the use of a residual resource of host interfaces without recovery. In case of repair of the unit in the reduction of interfaces field extension over the nominal tolerances are not allowed.

Repair technologies can be divided into four main stages:

1. Disassembly-washing.
2. Control-sorting.
3. Actually repair: restoration of micro and macro geometry surfaces of the parts and the physical and mechanical properties.
4. Assembling a preliminary control of parts arriving at the assembly.

Disassembly and washing operation is carried out in several stages: the outer washing machine, podrazborka, nodal sink, on the dismantling of parts, washing and cleaning of parts. All items to the control-sorting thoroughly cleaned of dirt and soot, degrease, rinse and dry.

The oil channels and holes in parts to clean, rinse under pressure and blow compressed air.

Details of aluminum and zinc alloys are not allowed to wash in alkaline solution used for cleaning steel and cast iron parts, as aluminum and zinc are soluble in alkalis.

In the process control of parts breakup, cracks, dents and other damage to the shell detect by visual inspection. At critical parts checked for cracks using a flaw. Dimensions of parts must be monitored in the most exposed areas. Gear teeth wear unevenly, and when the control should measure at least three teeth arranged at an angle of 120 ?�. Given the need to ensure continued gears during the turnaround spalling and chipping teeth on the working surface of the teeth of the fatigue nature are not allowed.

Assembly units, such as a rod with a cover of a rod, a cylinder block with main bearing caps, gear transmission and the main transfer can not razukomplektovyvat. The rest of the assembly units razukomplektovyvat possible, but if you decide to continue the operation of mating components without repair, they razukomplektovyvat inappropriate.

In all cases, parts repair welding and surfacing weld must not have slag inclusions, undercooked areas, undercuts and other defects. After welding the joint clean. Spatter removed, so they do not interfere with the installation of mating parts.

Holes worn or damaged threads reduced threading the increased size of the repair, welding holes and then threading the nominal size, staging and vvertyshey spiral threaded inserts. The use of threaded inserts is preferable for reasons of quality and recovery effort.

Insert a springy helix made of wire rhombic section. At one end of the helix is folded the process leash, whereby the insert is wrapped in pre-prepared hole.

The technological process of repair of the threaded holes using a helical insert includes the steps of: boring holes defect to a certain size, thread cutting therein corresponding to the size of the helical insert and a helical insert Screwing breaking of process nips on the leash.

The table shows the dimensions of the apertures and under the spiral thread insert used in the repair of automotive parts.

Sizes drills and taps spiral inserts

Nominal thread	Drill diameter, mm	Carving a helical insert
M5h0,8	5.2	M6x0,8
M6h1,0	7.0	M8x1,0
M8x1,25	8.7	M10h1,25
M10h1,5	10.5	M12x1,5
M11h1,0	12	M13x1,0
M12h1,75	12.2	M14h1,75
M12h1,5	12.5	M14x1,5
M14h1,25	14.7	M16x1,25
M14x1,5	14.7	M16x1,5
M16h1,5	16.5	M18x1,5
M18h1,5	18.1	M20x1,5
M20h1,5	20.5	M22x1,5

To repair the threaded holes spiral inserts produced a special kit, which includes: inserts, drills, taps, special keys for tightening inserts barbs for srubaniya technological lead.

Details supplied to the assembly must be clean and dry.

Threaded connections must be free of damage. Disposable self-locking threaded fasteners must be replaced with new ones. If you are unable to use new self-locking parts in the formulation of their old need to further loosen the stopper on.

When assembling installing new gaskets and seals. Rubbing the surface of the parts during assembly to lubricate clean oil. In formulating the rubber seals lubricate the working surface of the cuff to avoid damage during installation. When installing the seals with a metal case oil seal nest under Apply a thin layer of sealant.

The assembly of components and assemblies to perform in accordance with these Guidelines.

Use the measuring tools to check the dimensions prior to assembly of parts forming the landing.

When assembling the parts in conjunction with a movable landing should be provided free of relative movement without jamming. Sleeves, rings ball and roller bearings installed using mandrels. When pressing the bearing force should not be transmitted via balls or rollers. Tools for pressing must rest on the press-fit ring. Joining force should coincide with the axis of the bearing to prevent misalignment.

If the terms of the build installation of critical parts made with a hammer, it is necessary to use a mandrel and hammer-ferrous metals, plastics, rubber, as well as accessories for fitting parts.

The keys must be firmly planted in the shaft keyways with a hammer or arbor made of colored metal. Backlash dowels in slots shafts is allowed.

Studs should be wrapped tightly into the threaded holes without play. Items must fit over the stud bolts. Podgibaniem studs when installing them is not permitted parts, fastening assembly or parts of several nuts or bolts must be done uniformly on the perimeter - first preliminary and then final. All the nuts and bolts of the connection must be tightened with a torque.

In all cases, provided the leadership necessary to apply the keys that allow to limit torque.

Tightening torques, unless specifically stipulated in the technical conditions are determined depending on the diameter of the thread in the table.

Table Fastener Tightening

Thread diameter mm	Tightening kgs.m
6	0.6-0.9
8	1.4-1.7
10	3.0-3.5
12	5.5-6.0
14	8.0-9.0
16	12-14
18	16-19
20	23-27
22	30-36
24	42-48

Bolt must protrude from the nut (unless otherwise specified) in two-three strings of thread. Pins must not protrude from the slots nuts. The ends of the pins should be diluted and bent - a bolt and a nut on the other.

Tubes toplivoprivoda drive and brake at assembly to blow compressed air.