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I. Fill in the blanks: 1. The size of 0# drawing paper for drafting is ---4---- times that of 2# drawing paper. 2. 0# drawing paper for drafting is ----3--- times larger than 2# drawing paper. 3. The size of 1# drawing paper for drafting is ---4---- times that of 3# drawing paper. 4. 1# drawing paper for drafting is ----3--- times larger than 3# drawing paper. 5. There are generally three types of losses in centrifugal pumps: hydraulic loss, volumetric loss, and ----mechanical loss--------. 6. A mechanical seal consists of a --moving ring--, a --stator ring--, a sealing ring, elastic elements, etc. 7. Turbines are classified according to their thermal characteristics into —— condensing type ——, —— back-pressure type ——, extraction-condensing type, back-pressure extraction type, and multi-pressure type. 8 II. Judgment 1. The flow rate of a centrifugal pump refers to the volume of liquid discharged from the pump’s outlet. √ 2. The flow rate of a centrifugal pump refers to the volume of liquid drawn in at the pump’s inlet. * 3. Compared to centrifugal pumps, vortex pumps are generally used in applications requiring high head and low flow rates. 4. Vortex pumps cannot be regulated using an outlet valve; a bypass system should be used for regulation. 5. III. Single-choice questions 1. When chemical processing machinery is installed using shims, the slope of the inclined shims is generally--------- ； A: 1/5–1/10 B: 1/10–1/25 C: 1/20–1/50 2. When chemical processing machinery is installed using shims, the contact area between the shims and the foundation should generally be no less than ---------. A: 25% B: 50% C: 75% 3. When chemical processing machinery is installed using shims, the gaps between the shims are checked with a feeler gauge of —— mm; the total insertion length on both sides should not exceed 1/3–1/4 of the total width (or length) of the shims. A: 0.05 B: 0.10 C: 0.02 4. When chemical processing machinery is installed using shims, the total number of shims generally should not exceed 4 layers, among which there are ------ sets of inclined shims. A: 1 B: 2 C: 3 2. The cooling fan in our factory belongs to which type of fan? A: Axial flow fan √ B: Centrifugal fan C: IV. Multiple-choice questions 1. The methods for adjusting the flow rate of a centrifugal pump are: ------- A: Adjusting the discharge valve B: Bypass C: Adjusting the suction valve* 2. The methods for adjusting the flow rate of a reciprocating plunger pump are: ------- A: Adjusting the discharge valve* B: Bypass C: Adjusting the suction valve* D: Changing the speed 3. The axial force in a single-stage centrifugal pump can be managed by-------- A: Creating balance holes B: Using balance tubes C: Employing a balance disc structure* D: Arranging the impellers symmetrically* 4. The axial force in a multi-stage centrifugal pump can be managed by-------- A: Creating balance holes* B: Using balance tubes C: Employing a balance disc structure D: Arranging the impellers symmetrically True or False questions (one per question): The dimensional tolerance of a component refers to the maximum allowable variation in its relevant dimensions during manufacturing. (√) The sum of the absolute values of the upper and lower tolerances for a dimension is the tolerance. (√) The difference between cast steel and cast iron lies in their carbon content. (√) In worm and worm gear transmission mechanisms, they can serve as driving elements for each other. (X) When threading by hand, it is not allowed to use reverse rotation to remove or cut chips. (X) There is a protrusion in the middle of the thin part; this protrusion can be struck with a hammer to cause it to compress and deform, thereby achieving correction. (X) The classification of abrasives is such that the higher the grain size number, the coarser the abrasive. (X) Babbitt bearing alloys are divided into two main categories: lead-based and tin-based. (√) The advantage of the triangular scraper is that as it wears down, only its length decreases while the cross-section of the blade remains unchanged, thus ensuring a longer service life. (√) A dynamically unbalanced part can remain stationary at any position, but when it rotates, a couple is generated due to the uneven weight distribution along the axial direction. (√) For files that have come into contact with oil, they should be cleaned thoroughly with kerosene when not in use, and coated with a layer of chalk. (√) When sawing soft metals (such as copper and aluminum), it is not advisable to use a coarse-toothed saw blade. (X) The steel wire rope must be kept clean, and dry grease should be applied to it regularly. (√) When installing the saw blade, the tips of the teeth should face the worker, as it is the pulling force that performs the cutting action. (X) When filing the working surface with a file, ensure that the file is in such a position that the torque at both the front and back ends of the file is equal. (√) If processing costs are not considered, the lower the roughness of the workpiece’s surface, the better. (X) The nominal length of a V-belt is the length of its neutral layer. (X) When using an electric grinder for grinding, the operator should stand opposite to the grinder. (X) Labyrinth seals are primarily used for sealing gases and are non-contact seals. (√) Nitrile rubber can be used in environments with oil as well as in environments with ammonia. (√) The blackening flange treatment of commonly used materials is an oxidation treatment method, which can enhance the anti-rust ability of the surface. (√) Multiple choice questions (each question) 1. The following C does not belong to pipe fittings. A Reducer B Flange C Lens gasket 2. The following B flanges cannot be used in high-pressure situations. A Butt welding B Flat welding C Threaded flange 3. C Flaw detection method, which can detect internal defects in materials. A Coloring B Magnetic powder C Ultrasonic 4. Ventilation blowers are distinguished according to B. A flow rate B pressure C process location 5. Grinding method is used to repair mechanical parts, and the grinding allowance is generally B mm. A 0.3-0.5 B 0.005-0.3 C 0.001-0.005 6. In mechanical maintenance, grinding method is used to repair mechanical parts, and A is generally chosen as the grinding tool. A Gray cast iron B High carbon steel C Alloy tool steel 7. The working surface of the wedge key is A. Both sides B. Upper and lower sides. C A+B 8. The following B does not belong to the elastic coupling. A. Elastic cylindrical pin coupling B. Gear coupling C. Nylon pin coupling 9. Ra usually used in surface roughness is A. Profile arithmetic mean deviation B. Microscopic unevenness + point average height C. Maximum profile height 10. It cannot be used as a hydraulic pump in a hydraulic system. A Gear pump B Multi-stage centrifugal pump C Screw pump 11. The following heat treatment methods cannot be used as the final treatment of shaft parts. CA Quenching B Quenching and tempering C Annealing 12. B belongs to the chemical heat treatment of steel. A Normalizing B Carburizing C Quenching and tempering 13. Q235-A is steel. A Tensile strength B Compressive strength C Bending strength 15. The carbon content of low carbon steel is as follows A 0.15% B 0.25% C 0.35% 16. When the center distance of the two meshing gears changes (becomes larger), the transmission ratio will A become larger B remain unchanged C become smaller 17. The size of the hydraulic system pressure depends on A the rated pressure of the oil pump B the load C the flow of the oil pump 18. Among the following tolerances, Is the shape tolerance. A Verticality B Cylindricity C Coaxiality 19. Among the following pumps, they are positive displacement pumps. A Centrifugal pump B Gear pump C Vortex pump 20. When assembling an ordinary flat key, the mating surface is A, both sides B, upper and lower end surfaces C A+B 21. When the triangle belt is driven, the working surface is A, bottom surface B, both sides C A+B 22. When the key is connected during transmission, the key is subject to A torque B bending C Shearing 23. When grinding, choose the material of the grinding tool, which is A harder B softer than the material being ground C closer to 24. The assembly accuracy depends on the processing accuracy of the machine tool. This method is A. Modification method B. Complete interchange method C. Selection method 25. Which of the following valves have directionality, A. Gate valve B. Ball valve C. Stop valve Fill in the blanks (points for each question) 1. The size of the 0# drawing used for drawing is 4 times that of the 2# drawing 2. The 0# drawing is 3 times larger than the 2# drawing. 3. The widely used three views are the main view, the top view, and the left view. 4. The three basic sectional views are the full sectional view, the half sectional view, and the partial sectional view. 5. The tolerance of the Φ30 mm size is 0.5, and the minimum limit size is 29.8 6. The hole Φ30 mm, the shaft hole Φ30 mm, the maximum interference when mating is 0.15mm, the maximum gap is 0.025mm 7. 45 in 45# steel represents the carbon content in the steel is 0.45/100 8. The Cr content in 1Cr18Ni9 is 18/100 9. The thread angle of metric thread is 600, the thread angle of cylindrical pipe thread is 550, and the thread angle of trapezoidal thread is 300. 10. Two datums are usually selected for plane scribing, and 3 datums are usually selected for three-dimensional scribing. 11. Through scribing adjustment, the machining allowance of each processing surface is reasonably distributed. This method is called borrowing material. 12. There are two types of deformation of metal materials, one is plastic deformation and the other is elastic deformation. Correction is for plastic deformation. 13. Materials are corrected after plastic deformation. After correction, the hardness increases and the nature becomes brittle. This phenomenon is called cold work hardening 14. When storing shaft parts, vertical suspension is generally used to prevent stress deformation. 15. When machining shaft parts, the transition angle must be retained to prevent stress concentration. 16. For parts with a small aspect ratio, they can only be balanced. 17. Castings must be aged before processing. 18. Use a 0.02mm/m frame level to measure a working surface with a length of 500mm. The result is that the bubbles are offset by one grid, and the horizontal offset of the entire working surface is 0.001mm. 19. Mechanical seals are mainly composed of and compensation buffer mechanisms. 20. When installing centrifugal pumps and motors, they are generally installed first, and then installed. 21. Valve testing generally includes two types: test and spring. 22. Common springs are divided into two categories. 23. The basic hole system is a system of various fits formed for a certain hole tolerance zone and the tolerance zone of different shafts. 24. Surface roughness refers to the microscopic aggregate characteristics formed by the smaller and tiny parts of the parts being processed. 25. The maximum gap is equal to the algebraic difference minus the upper deviation of the hole, and the maximum interference is equal to the algebraic difference minus the lower deviation of the hole. 26. Among the fit codes, those with the molecule code H are, The code is h. 27. The base unit of length is, equal to mm. 28. The specifications of the vise commonly used by fitters are represented by jaws. 29. The desktop grinder commonly used by fitters is S1ST-150, and the representative of 150 is 30. In parallel belt transmission, the size of the transmission capacity is determined by the size of the wrapping angle between the belt and 31. In both parallel belt transmission and triangle belt transmission, the adjustment method can be used to tighten the belt. 32. Screw transmission is only used to convert motion into linear motion. 33. The most commonly used tooth curve of gears is 34. Usually rolling bearings rotate with the shaft diameter. 35. The code name of a rolling bearing is composed of a grade code and a number. 36. The ratio of the diameter of the large and small pistons of a hydraulic press is 5:1, then the ratio of the forces received by the large and small pistons is, and the ratio of the pressure of the liquid is 37. The relief valve is installed at the outlet of the hydraulic pump of the hydraulic system. Its function is to maintain the pressure of the hydraulic system and overflow when the hydraulic system is overloaded. 38. The commonly used centrifugal pump is 8B36A, which means the diameter of the pump suction inlet is mm and the lift is 39. The commonly used shaft seal forms of centrifugal pumps are and. 40. A set of mechanical seals has at least three sealing points. There are three unbalanced states of the rotor: 42. Use a lead pressure valve to detect that the clearance of the sliding bearing is 0.025mm, and the thickness of the shell split surface is 0.010mm, so the thickness of the shaft diameter lead wire is 43. The maximum interference between the hole of Φ350+0.025 and Φ35+0.033+0.017 is 44. According to the carbon content of steel, the carbon content of medium carbon steel is in between, and the S content of high-quality carbon steel does not exceed 45. For parts with the same size, the quenching temperature of 40# steel parts is higher than that of 40Cr. 46. The Rockwell hardness value is approximately equal to 47 of the Brinell hardness value. The scribing reference refers to the boundary of the required processing part on the workpiece, and the correction used in processing 48. The cutting amount of the drill includes the cutting depth, Three aspects. 49. There are three types of grinding abrasives: oxide abrasives, carbide abrasives, .50. The drilling depth is equal to the required screw hole depth plus 51. Lift check valves can only be installed to ensure flexible lifting. 52. Safety valves are divided into lever types, three types. 53. The function added between the friction surfaces is to reduce the friction between the two mutual contact surfaces. 54. There are three types of lifting equipment commonly used in maintenance work. True or False Question 1. The flat four-bar mechanism has a crank. ( ) 2. To prevent the two friction wheels from slipping during transmission, there must be sufficient pressure at the contact point of the two wheel surfaces. ( ) 3. According to the different rotation directions of the threads. The threads can be divided into clockwise left threads and counterclockwise right threads. 4. M24 * 2 represents an ordinary coarse thread with a nominal diameter of 24mm and a pitch of 1.5. () 5. The standard module and standard pressure angle of the gear are both on the indexing circle. ( ) 6. The axial force and circumferential component force generated by the helical cylindrical gear during transmission are related to the helix angle of the gear teeth and have nothing to do with the pressure angle. () 7. In the worm transmission, the worm can be used as the driving part or the driven part. () 8. The efficiency of worm transmission is related to the number of teeth of the worm gear. () 9. Gear trains can be divided into fixed-axis gear trains and epicyclic gear trains. () 10. Fixed-axis gear trains can convert rotational motion into linear motion. () 11. The key connection is a mechanical dynamic connection. () 12. The failure form of the key connection is that the wedged working surface of the key is crushed, extruded and destroyed. () 13. The part where the shaft is supported by the bearing is called the shaft head. () )14. All transmission parts that perform rotational motion must be mounted on a shaft to rotate and transmit power.( )15. Thrust rolling bearings can withstand radial force and axial force at the same time. 16. The inner ring of a rolling bearing has the same function as the bearing bush of a sliding bearing. () 17. Only a movable coupling can compensate for the offset between the two shafts. () 18. In terms of connection and transmission, the coupling and clutch have the same function. () 19. In hydraulic transmission, vertical pressure per unit area The force on is called the action force, and its unit is Pa. 20. When oil flows through channels with different cross-sectional areas, the flow rate at each cross-section is different. () 21. The working pressure of the hydraulic pump depends on the rated pressure of the hydraulic pump. () 22. In the geometric tolerance, the datum can be divided into a datum point, a datum line and a datum plane according to the different geometric characteristics. () 23. In the geometric tolerance, the symbol "≡" represents the degree of symmetry. () 25. Surface roughness refers to the microscopic geometric characteristics formed by the small spacing and tiny valleys and peaks on the machined surface of the part. () 24. The surface roughness symbol "" is a basic symbol. It is meaningless to use this symbol alone. () 25. The movable screw and nut of the vise should be regularly greased, and the jaws should be tightened when not in use. () 26. Measurement error refers to the error between the measured value and the true value. () 27. Straightening is a repair method for a bent shaft, usually done by cold calibration and hot calibration. () 28. The unbalance on the rotating parts is distributed in a single radial direction, which is called static unbalance. () 29. The fit properties of the components of the shaft diagram set include clearance, transition, and interference. () 30. There are two major categories of causes of mechanical rotor vibration, including structure and installation. () 31. According to the different forms of media, seals can be divided into two categories: gas and liquid seals. () 32. Mechanical seals are composed of a moving ring, a static ring, a compensation buffer mechanism and a transmission mechanism. ()33. Centrifugal pump impellers can be classified into open and closed impellers based on their structural design. ()34. After the repair of a centrifugal pump impeller, balancing and weight reduction must be carried out as required; cutting should be done on both sides of the impeller, with the thickness removed not exceeding 1/3 of the original impeller wall thickness. （）35. Different steel grades have different heating temperatures for heat treatment. ()36. Aging treatment is a phenomenon in which, by keeping a workpiece at room temperature or a lower temperature for an extended period of time, certain changes occur in its properties as well as its shape and dimensions. ()37. The commonly used 45# steel indicates an average carbon content of 0% in the steel. 45. 38. Ductile iron, like steel, can have its mechanical properties improved and enhanced through various heat treatment methods. ()39. The strength of a material refers to its ability to resist external forces without being damaged. () Multiple-choice question 1. In a crank-rocker mechanism, the crank will reach a \"dead center\" position during motion only when it is the driving element. A connecting rod B frame C rocker D connecting rod bracket. 2. In belt drives, motion is transmitted by means of . A. Power of the main shaft; B. Torque of the driving wheel; C. Friction between pulleys. 3. Connecting threads usually use screw threads. A Trapezoid B Toothed shape C Rectangle D Triangle 4. When the pressure angle on the pitch circle is 20º, the root of the tooth becomes narrower while the tip of the tooth becomes wider; as a result, the load-carrying capacity of the gear is A greater than B less than C equal to D higher E reduced 5. When the power to be transmitted is high, in order to improve efficiency, the number of starts on the worm can be A Z=1 B Z=2-3 C Z=4 6. Among the three types of ordinary flat keys, this type of key does not move axially within the keyway. A Round head B Flat head C Single round head 7. The correct fit between the inner ring of a rolling bearing and the shaft diameter is A Interference fit based on the base hole system B Transitional fit based on the base hole system C Clearance fit based on the base hole system 8. When the cross-sectional area of a hydraulic cylinder remains constant, the speed of movement of the cylinder depends on the . of the liquid that enters the cylinder. A Flow rate B Pressure C Load 9. The operating pressure of a hydraulic pump depends on . A Power B Oil flow rate C Load 10. Lubrication is an extremely important method for reducing and controlling A heat generation B transmission C friction 11. A cone marked as ⊿ 1:50 has a slope of A 1:50 B 1:25 C 1:100 12. Quenching is mainly used to improve the A hardness B strength C overall properties of steel 13. After carburizing steel, the toughness and plasticity of its core A increase B decrease C remain basically stable 14. Tap and die tools are generally made from A high-carbon tool steel B alloy tool steel C high-speed tool steel 15. Rolling bearings have the highest precision grade: A G B D C C 16. The working pressure of pressure vessels should be no less than A 1 Kg/cm² B 0.110 Kg/cm² C Kg/cm² 17. The safe voltage for working inside towers and tanks should not exceed A 12V B 24V C 36V 18. In a dimension chain, deviations affect the assembly accuracy of A each individual dimension B only the increasing-ring dimensions C only the decreasing-ring dimensions 19. To measure the radial runout of shaft components, one should use A a level B a dial indicator C a lever micrometer 20. In equipment installation, the slope of shims used for alignment is usually A 1:10 B 1:20 C 1:50 21. When maintaining centrifugal fans, the levelness of the fan casing should be measured with reference to A the motor shaft B the bearings C the casing 22. A gap must be left between the contact surfaces of any two components on the fan’s main shaft, and this is done for A expansion B pre-tensioning C positioning 23. The first-level maintenance of equipment should be carried out by A equipment technicians B operators C maintenance staff 24. When installing or removing bearings, the fit tightness between the shaft and the bearing is generally A greater than B equal to C less than that of the fit between the bearing and the housing 25. The machining precision of relatively moving components has an A greatest B smallest C moderate impact on the sealing performance of gaps 26. The bending radius when bending pipes must be greater than times the pipe diameter. A 3 B 4 C 5 27. To give the cutting part of a chisel a certain degree of hardness, quenching is necessary; the flame used for this purpose is A yellow flame B blue flame C golden-yellow flame 28. The heat-treated hardness of alloy tool steel cutting tools is HRC A 40-45 B 60-65 C 70-80 29. To improve the structure and machinability of metals, parts are usually subjected to annealing or normalizing, and this is generally done after. A Before processing B Before rough processing C Before semi-rough processing 30. An axis that is subjected only to torque or only to bending moment, or one that experiences a very small bending moment, is A Spindle B Drive shaft C Mandrel 31. The red lead powder used for lapping has very fine particles; it should be mixed with a small amount of A Engine oil B Water C Diesel 32. The measurement range of a vernier protractor is A 0-180° B 0-320° C 0-360° 33. When compressing valve packing, the seams between the layers should be offset by A 45° B 90° C 120° 34. The efficiency of screw transmission depends on the threads’ and the friction angle. A Pitch B Lift angle C Clamping angle Multiple-choice questions 1. For machines with a high center height or significant vibration, what slope is appropriate for the shims? A 1:5 B 1:10 C 1:20 D 1:50 2. During equipment installation, the height of the shim set is generally how many millimeters? A 5-20 B 10-50 C 30-70 D 50-100 3. During secondary grouting, it should generally be carried out hours after the concealed works have been inspected and approved and after the machine has been fully leveled. A 8 B 10 C 16 D 24 4. The taper of the pin in an elastic coupling is generally A 1:15 B 1:10 C 1:30 D 1:50 5. For precision components on machines, as well as connectors and mating parts that operate under temperatures above °C, an anti-seize agent should be applied to their surfaces during assembly. A 50 B 100 C 200 D 500 6. The contact angle between the bearing shell and the shaft diameter is A 30°-50° B 50°-60° C 60°-90° D 90°-180° 7. After the pipeline is finally connected to the machine, its radial displacement should be checked using a dial indicator on the coupling. For machines with a rotational speed of more than 6000 revolutions per minute, this displacement should not exceed ; for machines with a rotational speed of 6000 revolutions per minute or less, it should not exceed . Otherwise, the pipeline needs to be adjusted. A 0.005 B 0.02 C 0.05 D 0.10 8. When using the grouting method to place shims, the contact area between the shims and the foundation can reach A 25% B 50% C 75% D 100% 9. Austenitic stainless steel is prone to A stress corrosion B intergranular corrosion C crevice corrosion D uniform corrosion in CL-media. 10. Which of the following belong to positive-displacement pumps and which belong to vane pumps? A Plunger pump B Jet pump C Vortex pump D Gear pump E Single-stage centrifugal pump 11. The basic geometric parameters of pressure vessels are and A Diameter and wall thickness B Diameter and volume C Temperature and pressure D Diameter and pressure 12. In the welding of the following materials, spatter is not allowed to remain, as these small metal particles can cause electrochemical corrosion in the presence of corrosive media. A Gray cast iron B High-quality carbon steel C Bronze D Austenitic stainless steel 13. In non-destructive testing, which of the following materials cannot be inspected using magnetic particle testing? A Carbon steel B Red copper C Austenitic stainless steel D Aluminum 14. When marking, the unprocessed raw surface is used as a reference, and it can only be used times A 1 B 2 C 3 D 4 15. The coarseness of a saw blade is indicated by the number of teeth per mm of its length. A 10 B 25 C 50 D 100 16. In belt drive mechanisms, motion and power are transmitted based on the between the belt and the pulley. A Friction B Tension C Initial tension D None of these 17. The viscosity of 50# machine oil is A higher than that of 68# machine oil B lower than that of 68# machine oil C equal to that of 68# machine oil 18. In the compressor code 4M50-250/320, 50 represents A Displacement B Suction volume C Piston force D Pressure 19. The purpose of a sectional view is to clearly show the structural shape of a component. A Partial B External C Internal D Cross-sectional 20. Regarding the matching of materials for bolts and nuts in pressure vessels, it is generally required that the hardness of the bolt be A slightly lower than that of the nut B slightly higher than that of the nut C the same as that of the nut D either is acceptable 21. Bevel gears are used for transmission between two axes that are A parallel B intersecting C perpendicular D any of these 22. Among the following seals, which ones are non-contact seals? A labyrinth seal B expanding ring seal C mechanical seal D floating ring seal 23. The inner diameter of a 200-type bearing is A 5 B 10 C 15 D 20 Fill-in-the-blank questions 1. Views are divided into basic views, , views, and rotated views. 2. A complete part drawing includes the diagram, , technical requirements, and the title block. 3. A part drawing is a drawing that serves as a guide for the part. 4. Surface roughness is a criterion for evaluating parts. 5. The methods for marking dimensions on patterns include the method, the method, and the comprehensive method. 6. Marking work is actually carried out through two processes: marking and material borrowing, and these two processes are intricately linked together. 7. After marking, the spacing between the drill holes can be determined based on the curvature of the lines; drill holes must be made at the bends and turns in the lines. 8. The choice of the cross-sectional shape of the file depends on the shape of the workpiece. 9. The characteristic of a flat key connection is that it transmits torque through the key, and it can only be used to fix components on the shaft. 10. In machinery, in addition to serving a connecting function, pins can also serve other purposes. 11. The methods for checking gear backlash are and method. 12. The tooth shapes of splines are and shape. 13. Depending on the direction of application, cylindrical helical springs can be divided into compression springs, tension springs, and torsion springs. 14. The assembly drawing should indicate the performance dimensions, as well as five other important dimensions. 15. In the maintenance of chemical engineering machinery, the mandrel method and the autorefractometer method are commonly used to check the coaxiality of components. 16. The basic forms of welded joints include butt joints, lap joints, and other types of joints. True or False Question 1. Limit deviations include upper deviation and lower deviation. 2. When the tolerance grade of the hole is greater than or equal to IT8, the same-grade tolerance for the hole and shaft is adopted. 3. The universal angle ruler can measure any angle from 0 to 360°. 4. When making lines, it should always start from the line marking reference. 5. The angle between the back edge of the chisel and the cutting plane is the wedge angle. 6. The length of a saw blade refers to the distance between the centers of the mounting holes at its ends; fitters commonly use saw blades that are 300 mm long. 7. Reaming holes is done using reamers to refine holes that have been roughly drilled. 8. When the thread direction is clockwise, a thread that is screwed in is a right-hand thread. 9. M20*2-6H/6g, where 6H denotes the tolerance zone for external threads, and 6g denotes the tolerance zone for internal threads. 10. Scraping is characterized by large cutting volume, high cutting force, significant heat generation, and substantial deformation due to clamping. 11. The dimensional accuracy after grinding can reach 0.01-0.05mm. 12. The higher the grain size number of the powder, the finer the abrasive; the lower the number, the coarser the abrasive. The higher the grade of the fine powder, the coarser the abrasive; conversely, the finer the abrasive. 13. Epoxy resins exhibit good adhesion to various materials, which leads to their widespread use. 14. Positioning the workpiece with a cylindrical hole on a longer mandrel can restrict two degrees of freedom of the workpiece. 15. Any rotating component with a length-diameter ratio must be dynamically balanced. 16. The assembly sequence is from top to bottom, from inside to outside, from the easier tasks to the more difficult ones, and from tasks requiring high precision to those that require only standard precision. 17. When the interference amount of the fittings and the fit dimensions are small, the thermal expansion and contraction method is generally used for assembly. 18. The rolling bearing clearance increases due to heat generation when the bearing is in operation. 19. Excessive tension in belt drives reduces the forces acting on the shafts and bearings, which shortens the belt’s lifespan. 20. The side clearance between two meshing gears is independent of the center distance deviation. 21. Conduct daily inspections of the equipment in order to detect any abnormalities promptly and address them. 22. Centrifugal pumps generate pressure head in liquids by means of a rotating impeller. 23. Multi-stage centrifugal pumps are arranged in a single direction, allowing their radial pressure to be generated without the need for any additional measures. 24. The distance between the top dead center and the bottom dead center of the piston is called the piston stroke. 25. Piston compressors belong to positive displacement compressors. 26. The nominal diameter of a pipe generally refers to the inner diameter. 27. Gate valves are classified into stem-type and hidden-stem types according to their structural design. 28. The measurement accuracy of the frame level is 0.01 mm/m. 29. Seals are classified into dynamic seals, static seals, and labyrinth seals. 30. Gear oil pumps belong to hydraulic pumps. 31. The strength test for the safety valve is 1.25 times the system’s rated operating pressure. 32. Steel formed by adding alloying elements to carbon steel is called alloy steel. 33. Quenching and tempering refers to quenching followed by high-temperature tempering. 34. Gloves can be worn when using a sledgehammer. 35. The crankshaft of a piston compressor must be made of forged steel; it is not allowed to be made of cast iron. 36. The notches on piston rings usually come in three forms: straight notches, diagonal notches, and overlapping notches. 37. When working at heights, safety belts sometimes allow them to be worn low but used at a higher position. 38. The safe voltage for safety lighting lamps must not exceed 36V. 39. Using streamlined components to reduce fluid disturbance can minimize cavitation. 40. The heat treatment process in which steel is heated to a temperature above Ac3 or Ac1 and then cooled at a rate faster than the critical cooling rate to obtain highly hard martensite or bainite is called quenching. Multiple-choice question: 1. In a base hole fit, when the absolute value of the shaft’s basic deviation’s lower limit is greater than or equal to the standard deviation of the hole, it is a __ fit. A: Interference fit B: Transition fit C: Clearance. 2. Among the parameters used to evaluate surface roughness, the code for the arithmetic average deviation of the profile is A. Rg B. Ra C. Rz. 3. In a vernier caliper with a reading of (1/50), 50 divisions on the vernier align with 1 mm on the main scale. A 49 B 39 C 19 4. When using a universal protractor to measure an object, when the angle being measured is greater than 90° but less than 180°, what value should be added? A 90° B 180° C 360° 5. When machining internal threads of the same diameter in steel and cast iron components, the diameter of the bottom hole in the steel component is A slightly larger than that in the cast iron component B slightly smaller than that in the cast iron component C equal to that in the cast iron component 6. During the process of scraping, if some of the scraping points appear shiny after scraping, one should A scrape more heavily B scrape more gently C scrape neither too heavily nor too gently 7. The surface at the joint where bonding occurs should preferably be A rougher B smoother C either rough or smooth is acceptable 8. When positioning an outer cylindrical component within a sleeve hole, if the positioning reference and the positioning holes are relatively long, it is possible to limit the number of degrees of freedom. A. Two movements B. Two rotations C. Two movements and two rotations. 9. One of the basic requirements after assembling a turbine shaft assembly is that the symmetrical center plane of the turbine teeth should be A. parallel to the worm axis B. coincident with it C. perpendicular to it. 10. When tightening nuts or screws arranged in a rectangular pattern, one should start from A. the left end and move towards the right end B. the right end and move towards the left end C. the middle and work symmetrically from both sides. 11. When using an interference fit, it is necessary to ensure that the minimum amount of interference is A. equal to the minimum required for the connection B. slightly greater than it C. slightly less than it. 12. Bearings that can withstand both radial and axial forces are A. radial bearings B. thrust bearings C. angular contact bearings. 13. When assembling thin-walled bearing shells with bearings, in order to achieve a tight fit, an appropriate amount of interference is needed; the cross-sectional surface of the thin-walled bearing shell should be A. higher than that of the bearing housing B. lower than it C. at the same level. 14. The inner diameter of the rolling bearing with model number 129 is A. 29 mm B. 90 mm C. 145 mm. 15. When using belt drives, the wrap angle of the belt around the pulley cannot be A. greater than 120° B. less than 120° C. equal to 120°. 16. When installing involute cylindrical gears, if the contact points are in an incorrect position with asymmetric contact, the reason is that the axes of the two gears A. are skewed B. are not parallel C. have an excessive or insufficient center distance. 17. Compared to frame levels, spirit levels have a larger measurement range and A. better versatility B. higher precision C. easier use. 18. An important factor that causes displacement of the rotational center line of the spindle is A. the shape accuracy of the spindle B. the dimensional accuracy of the spindle C. the clearance of the bearings. 19. The shaft diameter that fits with rolling bearings, or the bore of the bearing housing, requires high standards in terms of accuracy. A Parallel B Perpendicular C Coaxial 20. For removing simply shaped, stationary mating parts, one can use A pulling method B pushing method C temperature difference method. 21. The degree of viscosity is measured using viscosity; the unit of viscosity used in China is A dynamic viscosity u B kinematic viscosity ν C Engler viscosity °E. 22. In a single-acting cylinder, as the piston moves from the top dead center to the bottom dead center, the volume inside the cylinder increases, and the pressure accordingly A decreases B remains constant C increases. 23. The piston is not a perfect circular ring but is open-shaped; its diameter in the free state is equal to the cylinder diameter. A is greater than B equals C is less than. Fill-in-the-blank question: 1. Low-pressure valves are used in applications where the pressure does not exceed 1.6 Mpa. 2. The C620 lathe (commonly referred to as model 20) can machine parts with a maximum diameter of 400 mm. 3. To evaluate the machining quality of a part, it is necessary to consider both the machining accuracy and the surface quality; machining accuracy includes dimensional accuracy, geometric accuracy, and positional accuracy. 4. For standard cylindrical spur gears to mesh properly, both the module and the pressure angle must be equal. 5. A kinematic pair in which two components are in surface contact is called a low pair. 6. A kinematic pair in which two components are in line or point contact is called a high pair. 7. The purpose of marking is to indicate the machining boundaries, machining patterns, inspection lines, and alignment marks on the blank or semi-finished product. 8. Common marking methods include the straight-line marking method and the hand scraping method; both involve checking using the method of marking reference points. 9. High-quality carbon steel is classified according to its carbon content into low-carbon steel, medium-carbon steel, and high-carbon steel. 10. The grade of lubricating oil refers to its dynamic viscosity measured at 40 degrees Celsius. 11. In the three-stage filtration system adopted by our company, the mesh size for the first stage of filtration is 60, that for the second stage is 80, and that for the third stage is 100. 12. The process of subjecting a workpiece to high-temperature tempering after quenching is called quenching and tempering treatment. 13. Pressure vessels can be classified into four categories based on pressure: low pressure, medium pressure, high pressure, and ultra-high pressure. 14. Grinding materials are generally divided into three categories: oxide abrasives, carbide abrasives, and diamond abrasives; they are usually made of chromium-containing alloy steel. 15. Depending on different connection requirements, riveting is divided into movable riveting and fixed riveting. 16. Positioning pins generally bear very small loads; to achieve positioning, at least 2 of them are usually used in practice. 17. There are 5 precision grades for rolling bearings, denoted as C, D, E, F, and G. 18. Compared with belt drives, chain drives can ensure an accurate transmission ratio and offer higher transmission power. 19. The advantage of belt drives is smooth operation and cushioning effect; however, slippage occurs under overload conditions, and the transmission ratio is inaccurate. 20. In a ratchet mechanism, the driving element is the pawl, the driven element is the ratchet, and the frame serves to provide fixation and support. 21. In hydraulic transmission, the pressure level depends on the load. 22. A hydraulic jack is essentially an energy conversion device that uses oil as its working medium. 23. The international unit of length is , which is equal to mm. 24. Reamers can be classified by usage into hand reamers and machine reamers; by the shape of the hole they are drilled, they can be divided into cylindrical reamers and conical reamers; and based on their structure, they are categorized as adjustable reamers and solid reamers. 25. On the outer surface of a twist drill, the rake angle is greatest while the clearance angle is smallest; as one moves closer to the drill bit core, the rake angle decreases while the clearance angle increases. 26. The thread profile angles include triangular, trapezoidal, rectangular, serrated, etc. 27. Threads can be classified into connection threads and transmission threads according to their purpose. 28. The process of using a scraper to apply a very thin layer of metal onto a workpiece in order to improve its machining precision is called scraping. 29. Common methods for grinding workpieces include moving the workpiece along a flat surface in an 8-shaped, 8-shaped-like, or spiral trajectory for grinding. 30. According to technical requirements, the process of combining several parts into components, or combining several parts and components into a machine, is called assembly. 31. The types of imbalance in rotating parts include static imbalance and dynamic imbalance. 32. Threaded connections are a type of detachable connection, which are divided into ordinary threaded connections and special threaded connections. 33. Bearings are classified into rolling bearings and sliding bearings according to the nature of friction between their working elements. 34. A typical split-type sliding bearing consists of a bearing housing, a bearing cover, split shaft bushing shims, and bolts. 35. Rolling bearings are classified into roller bearings, ball bearings, and needle bearings according to the type of rolling elements. 36. Common lubricants include lubricating oils, greases, and solid lubricants. 37. In the code of rolling bearings, the two digits from the right represent the inner diameter of the bearing. 38. A hydraulic pump is a device that converts mechanical energy into hydraulic energy; common types of hydraulic pumps include gear pumps and piston pumps. 39. The method of conducting regular inspections and maintenance based on the degree of wear of equipment is called planned maintenance. 40. Our company has determined that the main forms of equipment maintenance include maintenance due to accidents or failures, planned maintenance, and maintenance based on condition monitoring. 41. Belt drives are classified into flat belt drives, V-belt drives, and round belt drives according to the cross-sectional shape of the belt. 42. Common methods for expressing hardness include Brinell hardness, Rockwell hardness, and Vickers hardness. 43. Iron-carbon alloys with a carbon content of less than 2% are called carbon steel. 44. A compressor is a machine used to transport gases or increase their pressure. Based on different compression principles, compressors can be divided into speed-type (centrifugal) and volume-type (reciprocating) types. 45. True or False Questions 1. Objects that are capable of moving relative to each other are called components. √ 2. Helical cylindrical gear drives can withstand a certain amount of axial force. √ 3. The use of worm and worm gear transmission allows for a large gear ratio, as well as an intersection angle of 90 degrees between the rotational axes. √ 4. When using the chain hoist, it is necessary to keep the moving parts well lubricated, but oil must not seep into the friction pads. √ 5. Taking thermal expansion and elasticity into account, a certain gap must be left in the piston rings of reciprocating compressors. √ 6. Lift-type check valves can be installed in horizontal or vertical pipes. * 7. Spring-loaded safety valves are generally installed vertically to avoid affecting operation. √ 8. Seamless pipe Ф108*4mm means that the inner diameter of the pipe is 108 mm and the wall thickness is 4 mm. √ 9. Disc valves are used to open and close pipelines, and can also be used for regulation. √ 10. The difference between soft-toothed gear reducers and hard-toothed gear reducers lies in the hardness of the tooth surfaces of the transmission gears. . √ 11. The wrap angle of the small pulley for V-belts does not need to be greater than 120 degrees. * 12. When designing V-belts, in order to extend their service life, only the diameter of the small pulley is restricted, while the wrap angle is not limited. * 13. The wedge angle of the cross-sectional area of V-belts is 40 degrees, while the pulleys are designed with angles of 34 degrees, 36 degrees, and 38 degrees. √ 14. In chain drive, the tensioning wheel can be placed on the outside or inside of the slack side. √ 15. To prevent tooth engagement in gear drives, high-viscosity lubricants can be used. √ 16. Surface roughness is a type of microscopic geometric shape error. √ 17. In the production of ductile iron, it is often subjected to various heat treatment processes in order to obtain different matrix structures. √ 18. The cross-block coupling exerts additional loads on the shafts and bearings. √ 19. Radial sliding bearings cannot withstand axial forces. √ 20. Sliding bearings must be lubricated, while rolling bearings can do without lubrication due to their lower friction. * 21. The fit between the rolling bearing and the shaft is a transition fit based on the base shaft system. * 22. The fit between the outer ring of the rolling bearing and the housing is a transition fit based on the hole system*. 23. A stepped shaft facilitates the installation and removal of parts on the shaft. √ 24. All key connections are detachable connections. √ 25. The wedge joint working surface is the two side surfaces. * 26. The working surfaces of a flat key connection are the upper and lower surfaces. * 27. Gear trains can be divided into fixed-axis gear trains and epicyclic gear trains. √ 28. In a planetary gear set, any gear set that has a rotating geometric axis is referred to as the central gear. * 29. The gear ratio of a worm and worm gear is the ratio of the number of teeth on the worm gear to the number of starts on the worm. √ 30. In worm and worm gear transmissions, the worm is usually made of wear-resistant materials such as bronze. * 31. In worm and worm gear drives, the transmission efficiency is related to the number of worm heads. * 32. The distance between two gears is called the center distance*. 33. The more teeth there are, the more likely root cutting will occur. * 34. To facilitate assembly, the width of the pinion is generally greater than that of the gear. √ 35. Threads whose thread profile, major diameter, and pitch all meet the standards are standard threads. √ 36. The nominal diameter of pipe threads is the inner diameter of the pipe. √ 37. The diameter of a V-belt pulley refers to the diameter of the middle layer through which the cross-section of the V-belt passes. √ 38. In mechanisms, the cam is often the driving element. √ 39. The primary filter screen for gear oil is 60 mesh. * 40. Spare rotating equipment must be properly protected; it should not be rotated or switched frequently. * 41. High-pressure pipelines must be inspected every 6 years, while medium and low-pressure pipelines have an inspection cycle of 15 years. * 42. The commonly used flow control valves in hydraulic transmission systems are throttle valves and relief valves. * 43. Based on their structure, shafts can be divided into crankshafts and stepped shafts. * 44. Rolling bearings have many advantages, but they cannot replace sliding bearings. √ 45. When the bending radius of common steel materials is greater than 2 times their thickness, fracture generally occurs. * 46. After the workpiece deforms, it cannot return to its original shape due to plasticity; this phenomenon is called springback*. Multiple-choice questions: 1. The coupling that can compensate for the offset between two shafts without generating additional loads when operating at high speeds is (B). A: Flange coupling B: Gear coupling C: Cross-slider coupling 2. If one of the V-belts in a set becomes unusable, what should be done? (A) A: Replace all of them. B: Replace one. C: Replace some. 3. Bearings are used for supporting (C). A: Shaft shoulder. B: Shaft head. C: Shaft journal. 4. The length-diameter ratio of bearings needs to be calculated for (C). A: Rolling bearings. B: Sliding and rolling bearings. C: Sliding bearings. 5. Axes are classified as crankshafts and straight shafts based on their (B). A: Appearance B: Axial shape C: Function 6. In actual use, the drive shaft serves the purpose of (A). A: Only transmitting torque B: Only experiencing bending C: Both torque and bending 7. Depending on the (C) of the flat key, it can be classified into types A, B, and C. A: Cross-sectional shape B: Size C: Head shape 8. The axes of the worm gear and worm are (A) in space. A: Vertical B: Arbitrary C: Parallel 9. Self-locking property of worm and worm gear transmission (B). A: Does not have B: Has C: Depends on usage 10. The radius of curvature (C) at various points on an involute gear. A: Equal B: Determined by the smaller tooth size C: Not equal. 11. For gears with the same number of teeth, the larger the module (A) is, the greater the tooth shape and geometric dimensions of the gear. A: Larger B: Smaller C: The pressure angle increases. 12. Connecting threads are most commonly used with (A). A: Triangle B: Trapezoid C: Sawtooth shape 13. The thread angle of (C) is 55 degrees. A: Ordinary thread B: Pipe thread C: Trapezoidal thread 13. The lubricating oil used in the compressor crankcase is (B). A: 150# compressor oil B: 68# machine oil C: 150# machine oil. 14. Packing-type clean water pumps and hot water pumps allow some leakage, but generally it should not exceed (A) drops per minute. A: 20-40 B: 40-60 C: 60-100 ? 15: Pumps equipped with mechanical seals are not allowed to leak at the beginning of operation, and the leakage rate should not exceed C drops per minute at the end of operation. A: 15 B: 30 C: 5 15. Among the principles of \"not letting equipment accidents go unaddressed,\" which one corresponds to (B)? A: Do not let go if the person responsible is not punished. B: Do not let go if there are no preventive measures in place. C: Do not let go if the economic losses are not clear. 16. The standard length indicated in the model number of a V-belt is (C). A: Circumferential length of the neutral layer B: Calculated length C: Inner circumferential length 17. The designation for the black metal material of grade QT40-17 is (A). A: Ductile iron B: Gray cast iron C: Alloy cast iron 18. For high speed and light loads, (A) should be chosen. A: Lubricant with low viscosity B: Lubricant with high viscosity C: Grease 19. Which of the following (B) belongs to the urea-grade stainless steel? A: 0Cr18Ni9Ti B: 0Cr18Ni12Mo2N C: 3Cr13 20. 0Cr18Ni9Ti is (C) type of stainless steel. A: Ferrite B: Pearlite C: Austenite 21. Spring-loaded safety valves are divided into closed and open types; (A) closed type valves are generally not used in equipment. A: Steam B: Flammable and explosive C: Toxic substances. 22. The heat treatment method in which the workpiece is heated to a temperature below the AC1 point of steel, held at that temperature for a certain period of time, and then cooled (usually to room temperature) is called (C). A: Quenching B: Annealing C: Tempering D: Normalizing. 23. The component for which dynamic balancing is not required is (A). A: Crankshaft B: Motor rotor C: Turbine rotor D: Fan rotor 24. The incorrect classification of bearings based on the direction of the load they bear is (B). A: Centrifugal bearings B: Self-aligning bearings C: Thrust bearings 25. The following is not a type of check valve structure: (B) A: Lift-type B: Spring-type C: Swing-type 26. The correct classification of pressure vessels according to their pressure rating is (A). A: High-pressure vessels B: Class I vessels C: Heat exchangers 27. The heating temperature of bearings is generally controlled below (C) degrees. A: 150 B: 80 C: 120 28. When performing dynamic balancing on a fan rotor or motor rotor, it is not necessary to use (A). A: Radial bearings B: Couplings C: Coupling pins 29. When using shims to install equipment, the number of shims in each set should not exceed (B) pieces. A: 2 B: 4 C: 6 30. The material of the valve body for the globe valve J41H—25, Dg50 is (C). A: Stainless steel B: Cast iron C: Cast steel 31. The silicon content in alloy steel 60Si2Mn is (B). A: 0.2% B: 2% C: 20% 32. 35# steel belongs to (A). A: Medium-carbon steel B: Low-carbon steel C: High-carbon steel 33. Since connecting rod bolts are subjected to large loads, they generally do not use the following (A) type of material. A: 35 B: 40Cr C: 35 CrMoA 34. Quenching and tempering should be carried out at (C) time. A: Before processing B: After processing C: After rough processing 35. A crank mechanism refers to a component among two connecting rods that is capable of moving in a full circle (C). A: Oscillation B: Back-and-forth motion C: Rotation IV. Short-answer questions 1. Briefly describe the working principle of a safety valve. 2. What is the purpose of preloading rolling bearings? 3. Briefly list the functions of lubricating oil: lubrication, cooling, removal of debris, and corrosion prevention. V. Drawing 1. VI. Calculations 1. It is known that the dimensional accuracy required for a certain spindle shaft is Φ200–0.05 mm, while the measured size of the bearing sleeve is Φ200 mm. What are the maximum and minimum clearances between this spindle shaft and the bearing sleeve? 2. In the compound gear train shown in the figure below, if the rotational speed of shaft 1 is n1 = 730 revolutions per minute, what is the rotational speed of shaft 4? Is the direction of rotation of shaft 4 the same as that of shaft 1? Maintenance I. Leveling of the machine: There are no specific regulations; generally, the allowable tolerance is 0.10 millimeters per meter in the horizontal direction and 0.05 millimeters per meter in the vertical direction. It is not allowed to use adjustable foot bolts to adjust the levelness. Alignment reference: the machined surface of the machine body ； Guiding surface supporting the sliding component (mid-body, cylinder piston) ； Axial diameter of rotating components ； End face and outer circle of the coupling ； Other surfaces with higher machining precision. II. Assembly of rolling bearings: 1. The bearings should be clean, free from damage or rust, and should rotate smoothly without any abnormal noises. 2. The force must act evenly on the end face of the bearing ring. Special tools are suitable for use. 3. When oil heating is used for interference fit, the oil temperature shall not exceed 120 degrees. 4. The bearing ring should be in close contact with the shaft shoulder or the bearing seat retainer. There is a certain gap between the outer ring of the bearing and the bearing cover; according to the requirements in the technical documents, this gap should generally not be greater than 0.1 millimeters. 5. When the bearing is installed in a split-type bearing housing, the bearing cover and the housing must fit tightly together. III. Sliding bearings: The alloy layer is required to be firmly bonded (by tapping); there should be no defects such as delamination, cracks, pores, or double layers. Assembly requirements: For thick-walled tiles, 1. The back of the tile must fit tightly and evenly against the bearing seat; the contact area should be at least 50%, as determined by coloring tests. 2. The bearing shells and bearing seats should generally have an interference of 0.02–0.04 millimeters. 3. For the contact between the bearing shells and the shaft journals, a coloring method is used; the contact angle is 60–90 degrees, with uniform contact within the contact area, at 2–4 points per CM2. Otherwise, grind and lube. 4. The clearance of the bearing shells meets the requirements; generally, the lateral clearance is half of the end clearance. Thin-walled tiles: 1. The back of the tile must fit tightly and evenly against the bearing seat; as checked by coloring, for tiles with an inner diameter of less than 180 millimeters, the contact area should be at least 85%, while for those with an inner diameter greater than 180 millimeters, the contact area should be at least 70%. 2. The fit clearance and contact surface between the bearing shells and the shaft journals are ensured through machining; scraping is generally not permitted. If the axial contact is uneven, slight adjustment can be made. 3. After assembly, check the mid-surface with a 0.02 mm feeler gauge; no insertion is allowed. 4. (The interference between the bearing shells and the bearing housings is determined according to the instructions.) 5. Radially self-adjusting bearings with multiple oil wedges rely on machining precision to ensure a proper fit between the bearing shells and the shaft journals; the contact surfaces generally do not require lapping. 6. If the upper tile is also under load, the same requirements apply to both the upper and lower tiles. Thrust bearing shell: It should make even contact with the thrust disc, with the contact area being no less than 75%. The gap matches the machine file. IV. Installation of shaft seal soft packing 1. The packing rings should be cut with 45-degree notches, pressed together with overlapping sections, and the joints between the two rings should be offset by 90 degrees. 2. The pressing depth is generally equal to the height of one turn of packing, but shall not be less than 5 millimeters. 3. For V, U, and Y-type seals, do not compress them too tightly; the groove should face the side with higher pressure. When linear expansion is large, the effect of temperature must be taken into account. Assembly of mechanical seals: 1. The parts must not be damaged or deformed, and the sealing surfaces must be free from defects such as cracks or scratches. 2. Keep it clean during assembly. Especially the stationary and rotating rings. 3. The moving ring can move freely on the shaft. 4. The compression level meets the file requirements. 5. The rotor rotates smoothly after installation. 6. The flushing and sealing systems must be clean and free of foreign objects. V. Gear Assembly 1. The center distance deviation between the two gears, as well as the meshing clearance, shall conform to the machine specifications. When using the lead compression method to check the meshing clearance, the length of the lead strip should be at least 5 tooth pitches. There should be no fewer than two along the length of the tooth, arranged evenly. The center distance should be checked if necessary. 2. Use the coloring method to inspect the contact surface of gear meshing; the contact spots are distributed along both the tooth height and tooth width directions. 1. Alignment references for machine installation 2. Assembly requirements for rolling bearings 3. Assembly requirements for sliding bearings (thin-walled bushings). 4. Requirements for mechanical seal assembly 5. How to check the meshing clearance and contact surface of drive gears?