Abstract: Disassembly is an essential step in the repair of agricultural machinery in China. Incorrect disassembly methods and tool usage often expand the scope of component damage and reduce repair efficiency. This article introduces the disassembly of threaded connectors and non removable connectors in agricultural machinery, as well as the disassembly methods and key points for those who are not familiar with the machinery, in order to improve the repair quality of agricultural machinery.

Keywords: agricultural machinery; Typical components; disassemble

The working environment of agricultural machinery is harsh, and its external connectors are prone to rusting and death. Dismantling is also an essential task in agricultural machinery repair. During dismantling, it is common to encounter the dismantling of broken bolts, rusted bolts, static fittings, and non removable connectors, which brings great difficulties to agricultural machinery repair work. If one blindly tightens and forcefully knocks, it will only damage the machine parts, cause unnecessary economic losses, increase repair costs, and reduce repair quality.

1. Disassembly of threaded connectors

Dismantling of threaded connections. Threaded connections are widely used in agricultural machinery, with advantages such as simple structure, easy adjustment, and multiple disassembly and assembly. Although it is relatively easy to disassemble, sometimes damage can occur due to insufficient attention, improper tool selection, incorrect disassembly methods, etc. Therefore, it is important to choose a suitable wrench or flathead screwdriver and avoid using a flexible wrench as much as possible. When disassembling, the positive and negative directions of the thread should be clarified first, and a suitable wrench should be selected. When disassembling, the reason should be analyzed, and the relay rod should not be arbitrarily extended to avoid breaking the bolt. Before disassembling threaded connectors, it is necessary to carefully observe them. Some threaded connectors are located in a concealed position and can be easily overlooked if not careful, such as the oil pan fastening bolts of Dongfeng 50, Hongqi-50, and 495 diesel engines. One of them must be disassembled from the engine and tractor before disassembly, and should be carefully inspected.

1.1 Disassembly of Double Headed Bolts

Double headed bolts generally have different size specifications at both ends, with one end having fine threads and the other end having coarse threads. Moreover, due to the use of interference fit threads at one end of the bolt embedded in the body, it is not necessary to disassemble it when necessary. When disassembling, it is advisable to use a specialized wrench. If there are no specialized tools available, two nuts can be used to screw in the double headed bolt, and the lower nut can be turned to unscrew the bolt. This method does not require specialized tools and is widely used.

1.2 Disassembly of multi bolt connectors

Multiple bolted connections, such as oil pan, cylinder head, clutch, gearbox, etc. When disassembling multi bolt connectors, in order to prevent uneven stress during disassembly that may cause deformation and damage to the parts, all bolts should be loosened 1-2 times in a symmetrical and intersecting order, and then removed one by one.

1.3 Disassembly of important bolts and nuts

When disassembling important bolts and nuts, a torque wrench is generally used. In order to prevent deformation caused by uneven force on the components, disassembly should be carried out in an outward inward and diagonally intersecting order, and should not be done at once. First, tighten all bolts 1-2 times, and then divide into 2-3 times. Important bolts are required to have a certain tightening torque. If there is no specified torque value in the manual, a torque wrench should be used to check during disassembly for installation reference.

1.4 Disassembly of broken bolts

Drill a small diameter hole at the end of the bolt, tap the thread with a left-hand thread tap, and then screw in the left-hand thread screw to unscrew the original broken bolt. Drill a hole on the head bolt, insert a quenched conical rod (rectangular cross-section or with left-hand threaded groove) into the hole, drive it into the hole wall, and then rotate the conical rod to unscrew the head bolt. For bolts that cannot be disassembled, a drill bit with a diameter 0.5-1mm smaller than the bolt thread can be used to drill out the screw, and then a tap with the same thread as the bolt can be used to unscrew it. But if the threads of the original threaded hole are damaged during drilling, larger bolts need to be selected and re threaded.

1.5 Dismantling of rusted threaded fittings

Rusted threads are generally caused by the phenomenon of adsorption and meshing under long-term pressure, or by the adhesion of the two due to oxidation and rusting. To remove rusted threads, methods such as soaking in kerosene, hammering to loosen, or heating to expand can be used to loosen and unscrew both. Kerosene has strong permeability. After being immersed in kerosene, kerosene can penetrate deeply into the rust layer, making it loose and easy to disassemble. Tap around the nut to loosen the rust layer and make it easy to disassemble. After being penetrated or loosened by kerosene, Z should be tightened and loosened first. Repeatedly tightening and loosening can cause the rust layer to be exposed

2. Disassembly of static fitting parts

During the disassembly process of agricultural machinery, there are often some static fitting parts that need to be disassembled, such as rolling bearings, gears, pulleys, etc. When disassembling these parts, special attention should be paid to the following points:

(1) When disassembling static fitting parts, it is necessary to avoid damaging their working surfaces and damaging their fitting properties. Suitable specialized tools such as pullers and presses should be selected as much as possible. If there are no specialized tools and a hand hammer is needed for disassembly, a copper rod or wooden block should be used as a cushion to prevent the hammer from directly hitting the surface of the part and damaging it.

(2) The disassembly method of static fitting parts is related to the size of the interference fit. When the interference fit is small, such as the crankshaft timing gear, a puller should be used as much as possible for disassembly. When there is no puller, it can also be removed by gently tapping with a copper hammer. When the interference fit is large, the heating containment method should be used for disassembly. When the container is about to be heated to a certain temperature, quickly press it out with a press.

(3) Before disassembly, check whether there are auxiliary fixing parts such as pins, screws, and snap springs on the parts. If there are, they should be removed first to avoid damaging the interference fit parts.

(4) When disassembling, the force bearing part of the component should be selected correctly, the force should be evenly applied, and the resultant force of the force should be located on its axis. When disassembling the rolling bearing, the puller claw should hook onto the inner ring of the bearing, and the stressed part should be on the inner ring of the bearing to avoid damaging the bearing. When disassembling the rolling bearing in the bearing seat hole, the outer ring of the bearing should be subjected to force.

3. Disassembly of non removable connectors

Non detachable connectors, including welded and riveted parts. Non detachable connectors belong to permanent connections and are generally not disassembled during repairs. They are only disassembled when the connecting material needs to be replaced. For example, if the friction plate on the clutch wears out beyond the limit, the rivet should be removed and replaced with a new friction plate. The disassembly of welded parts can be done by sawing, plasma cutting, or drilling holes with a small drill bit before sawing or chiseling, or by using methods such as oxyacetylene flame gas cutting. The disassembly of riveted parts can be done by chiseling off, sawing off, or gas cutting off the rivet head, or drilling off the rivet with a drill bit. During operation, care should be taken not to damage the base components.

4. Not very familiar with mechanical disassembly

When dismantling machinery that you are not very familiar with, be especially careful and remove every part, such as shafts, gears, etc; Small items such as snap rings, gaskets, seals, etc. should be neatly arranged in order. Before understanding the connection form of the components, do not forcefully smash or pull them to avoid damaging the machinery.

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