Requirements for cylindrical surfaces. Test for PM04 Performing work by profession turner “Machining holes. What affects tool life
The experience of domestic and foreign mechanical engineering shows that it is advisable to increase the accuracy of manufacturing precision parts to a level that ensures their fit-free assembly. The most difficult to manufacture is an atomizer having cylindrical and conical precision surfaces. To ensure the requirements for smooth movement of the needle in the body (mobility), the diametral clearance in this pair must exceed the total combination of deviations from the correct geometric shape of the cylindrical guide surfaces and the curvature of their axes. The values of deviations from the geometric shape of the cylinder and the curvature of its axis achieved in the practice of manufacturing are separately analyzed parameters for the body opening 0.2-0.6 µm, for the guide needle 0.1-0.3 µm. Taking into account the possible deformation changes in these geometrical parameters in the housing in the direction of increasing up to 0.2 -0.5 microns from the forces of mounting loading, the minimum diametrical gap in the spray nozzles of diesel locomotive diesel engines must be at least 3 microns. In this case, the highest probability of collection of 1 sprayer will be ensured with the exception of sticking and freezing of the needle.
The maximum diametrical clearance for atomizers during manufacture should not exceed 4.5-5.0 microns, in operation in atomizers operating in fuel systems without unloading fuel injection lines from a residual pressure of 6.5 to 7.5 microns and in systems with full unloading 11 - 15 microns. It should be noted that an increase in the diametrical gap should not be accompanied by an increase in the tolerances for the geometric accuracy of the shape of the cylindrical surfaces of the atomizer, since these surfaces are also basic when machining a conical precision surface.
The performance and collection of the atomizer also depend on the ratio of the total value of the radial runout of the conical locking surfaces and the diametrical gap. For constructive
1 Ensuring performance requirements for the dimensional configuration of precision parts in pairs.
sizes of atomizers of injectors of diesel engines, the total value of the radial runout should not exceed the diametrical clearance. Otherwise, the tightness of the conical seal of the atomizer is violated due to the mismatch of the centers of the sealing sections, and there is a possibility of an increase in unevenness at low feed rates. This circumstance is associated with a change in the shape of the slot of the conical flow part (from annular to crescent-shaped) at small lifts of the needle, caused by the installation of the needle with a warp in the guide hole of the body. The total runout of the cones is 2-4 µm (in the body 1-3 µm, in the needle 1 µm) is practically achievable in serial production.
Radial runout is a complex geometric parameter representing the vector sum of misalignment and roundness. When the centers of sections coincide along the sealing belt, deviations from roundness, determining the area of the gap at the contact point, independently affect the quality of the tightness of the spray cone. In accordance with the experimental data in the spray nozzles of diesel locomotive diesel engines, the complete absence of moisture, estimated according to the method of GOST 9928 - 71, is achieved with deviations from the roundness of the sealing section of the conical surface of one of the parts of no more than 0.8-1.0 μm, and their total combination of deviations roundness at the point of contact should not exceed 1.6 microns at a pressure of the beginning of injection p 0 = 30 ... 32 MPa and 2 microns at p 0 = 20 ... 22 MPa.
The quality of fuel atomization and the injection characteristics of the atomizer, in addition to deviations in size, are also influenced by geometric parameters.
meters that determine the shape of the flow cone of the atomizer. These parameters include the difference in the angles of the sealing cones and deviations from the linearity of their generators. According to experimental data, the optimal difference in angles, which ensures high-quality spraying, starting from low pressures of the beginning of injection, is 30-50 ". With a decrease in the difference in angular ratios until the angles merge (over a cone length of more than 0.6-0.8 mm) or increase angle differences up to 1°40"-1°50" there is a sharp deterioration in the quality of atomization. Permissible values of deviations from the linearity of the forming cones, measured at a length of 1.5 - 2.0 mm below the large diameter section, which do not affect the quality of atomization and deviations flow characteristics in the zone of minimum feeds are 1.5 - 2.0 microns.
It should be noted that the considered geometrical parameters of the cones provide high-quality operation of the atomizers only in combination with correctly selected roughness parameters, which for a conical seal should not exceed Ra = 0.100 μm.
In table. 22 shows the main technical requirements for the geometry and roughness of precision sprayer surfaces in accordance with GOST 9928 - 71, as well as those recommended, based on experimental research data, for use in the manufacture and restoration of diesel engine injector sprayers using the technology of non-adjustable assembly. For comparison in table. 22 also shows similar parameters achieved in the serial production of diesel injector nozzles of the D49 type and obtained as a result of selective measurements of nozzles of some leading foreign companies.
The State Standard 9927 - 71 provides for the following requirements for the accuracy of the geometry of the precision surfaces of the parts of the plunger pair:
spray surfaces
| Radial runout of the cone, µm | Deviation from roundness of the cylinder, microns | Average diametral clearance, µm | Roughness Yaa, | MKM | ||||
| cylinder | cones | |||||||
| needles | corps | needles | corps | needles | needles | corps | ||
| 2 | 3 | 0,5 | 0,5 | At least 2 | 0,040 | 0,160 | 0,32 | |
| 1 | 2 | 0,3 | 0,5 | 3,5-4,5 | 0,040 | 0,080 | 0,100 | |
| 1,0-1,3 | 1,2-2,0 | 0,3-0,6 | 0,3-0,5 | 2,5-3,5 | 0,040-0,050 | 0,145-0,18 | 0,040-0,065 | |
| 0,4-0,8 | 1,0-1,4 | 0,2-0,3 | 0,2 | 3,3-4,2 | 0,034-0,052 | 0,078-0,090 | 0,052 | |
| 0,8-1,0 | 0,9-1,6 | 0,3-0,6 | 0,2-0,5 | 4,0-4,8 | 0,038 | 0,040 | 0,045 | |
| 0,6 | 1,4-3,1 | 0,2-0,3 | 0,1-0,4 | 4,2-4,8 | 0,034-0,040 | 0,063-0,070 | 0,042-0,059 | |
| - | - | 0,3-0,4 | 0,2 | _ | 0,044 | 0,075 | - | |
| 0,8-1,2 | 1,2-2,0 | 0,1-0,3 | 0,3-1,0 | - | 0,060 | 0,088 | - |
Form deviations of working surfaces, plunger / sleeve:
Similar requirements are provided for the valve pair:
Deviations of the form of cylindrical working surfaces, (valve / valve body):
from roundness, micron 3/3
taper, micron 3/3
Radial runout of conical and 5
external cylindrical surfaces relative to the axis of the valve, microns
Radial runout of the housing cone 4
valve relative to the cylindrical guide surface, microns
In the manufacture of plunger pairs using the technology of non-adjustable assembly (pair grinding), the taper tolerance can be reduced by 1.5 - 2 times. The technological diametrical clearance for pairs with a plunger diameter of 13 - 20 mm is 2.5 -3.5 microns, the roughness of the mating surfaces is not more than: for the cylinder Ra = 0.04 microns, for the sealing end Ra = 0.125 microns. For valve pairs, the diametrical clearance along the girdle and the guide of the cylindrical part is 10-15 microns, the roughness of the cylindrical and conical surfaces is not more than 7?d = 0.16 microns.
Improvement in the means of metrological control has a significant effect on improving the accuracy of manufacturing and assembling precision pairs. Measuring tools should provide not only barrage control, but also operational control of technological processes, which makes it possible to consistently obtain high-quality products. At domestic factories, measuring instruments for acceptance control of unified series such as TsNITA-82 and TsNITA-36 have found wide application. In VNIIZhT, using the schematic diagrams created at CNITA, devices for acceptance and inspection control have been developed in relation to the standard sizes of parts of the fuel equipment of diesel locomotives.
When measuring diametrical dimensions, shape deviations and curvature of the axes of the cylinders, the following are used:
Rice. 109. Schematic diagram of the measuring device of the instrument TsNITA-8243:
1 - measured part; 2 - measuring lever; 3 - regulation sector; 4 - spring; 5 - scale; b - optical system; 7 - sensitive element; 8 - support with an optical measuring head (optimator) of type 01-P or 02-P, having a division value of 0.1 and 0.2 microns, respectively; for internal precision surfaces - devices such as TsNITA-8243 (Fig. 109) or pneumatic length gauges (rotameters) DP.
The measuring device of the TsNITA-8243 instrument uses a differential measurement scheme using an elastic sensitive element 7 of a spring-optical transducer, similar to that used in the opticator and fixed on the measuring arms 2. The arms are mounted on supports 8 and move in the same plane, contacting the surface of the measured part 1 at opposite points. The deviation of the levers from the position corresponding to the setting for the size leads to the operation of the elastic element of the transducer and the deflection of the mirror fixed on it. The optical system 6 with the illuminator projects the beam reflected from the mirror onto the scale 5. The constancy of the gear ratio of the spring-optical transducer allows you to adjust the device to the size of one ring with the adjustment of the position of the beam on the scale by the adjusting sector 3. The introduction of a compensating device into the design of the device reduces the systematic temperature error. The mean square deviation during measurements on the TsNITA-8243 device does not exceed 0.1 µm with a measurement range of up to 30 µm.
The disassembled scheme is also applicable for measuring external surfaces. When two measuring mechanisms for internal and external measurements, working on a common scale, are placed in one body of the device, it becomes possible to directly obtain information about the diametrical gap in a pair. Such a constructive solution is implemented in the TsNITA-8295 device, which allows you to complete precision pairs without prior sorting into size groups. To improve the accuracy and automation of the assembly of precision pairs, the CNITA proposed a method of automated individual selection of parts for assembly using a computer.
When measuring internal holes, it is especially important to exclude the error of certification of the actual dimensions of the exemplary setting rings. The most convenient method, which allows checking exemplary rings directly in factory laboratories, is a method based on measuring the gap between a cylindrical shaft of known diameter and the measuring surface of the ring. The method is implemented in the TsNITA-3840 device, where the ring and the shaft alternately contact the opposite generatrices of the cylinder, which lie in the same diametrical plane. The measurement is made by an optic head with an error not exceeding 0.2 µm.
For selective measurement of deviations from roundness of cylindrical and conical precision surfaces, universal measuring machines-kruglometers are used, including models 218 of the Kalibr and Thalerund plants (England). Krugograms of a real profile are recorded in a section, the axis of which is preliminarily aligned with the axis of the precision spindle of the round gauge. Comparison of the deviations of the round chart points from the adjacent circle is performed by superimposing a template on the record. The scheme of the device for the acceptance operating evaluation of deviations in the roundness of conical surfaces (Fig. 110) has a main base surface,
Rice. ON. Schematic diagram of a device for measuring deviations from the roundness of the conical surface of the spray needle, which is an adjacent profile (circle) in contact with the conical surface of the part being checked. The base surface is made in a hard-alloy ring 4, which has a slot for a measuring tip in contact with the measured surface in the same contact section. The cylindrical surface of the part 7 is based on the supporting annular support 2, reinforced in the same way as the ring with the adjacent profile, in the installation housing 3. The drive mechanism 1 serves to rotate the part and press it through the telescopic cardan shaft to the base surface. When turning the part, the tip with the measuring arm 5 will have deviations by the value of out-of-roundness in the measured section. As a deviation recorder 6, an optic head or a recording part of a profilograph is used.
The scheme (Fig. 111) of a device for measuring the radial runout of the cone of the atomizer body provides for basing the body 1 with a cylindrical hole on a device rigidly fixed in the body
Rice. 111. Schematic diagram of the TsNII-7003 instrument for measuring the radial runout of the cone of the sprayer body on a prismatic mandrel 2. The part is rotated by the drive mechanism using a seamless belt that creates a force in the vertical plane, while the longitudinal displacement of the sprayer body is limited by the spherical tip of the movable stop 3, abutting against the cone . The tip of the stop is fixed in a tubular rod suspended on a hinge having two degrees of freedom. The tip of the measuring lever 4 passes through the groove in the spherical tip (stop) and contacts the conical surface in the horizontal plane. roller slide 5 of the entire measuring unit parallel to the generatrix of the cone.Mechanical amplitude oscillations of the measuring arm, caused by a mismatch of the shape and position (beat) of the measured conical surface relative to the cylindrical surface of the atomizer body, are converted into electrical signals by means of an inductive sensor 6 and an electronic unit 7, which are recorded on indicating 9 and recording 8. The disassembled circuit is applicable for measuring the beating of the conical surface of the needle and is implemented in the TsNITA-3613-TsNII-7007 operational control devices with registration of deviations on the optic head.
To measure the displacement of the cone, instruments made according to the CNITA metrological scheme (Fig. 112) are used. The atomizer rotates on a rigid cylindrical mandrel 6 with the cone surface resting in a circular probe-tip 8. The vertical movement of the tip 8 mounted on the lever 5, caused by the displacement of the cone center relative to the base cylindrical precision surface, is fixed by the measuring head
Rice. 112. Structural diagram (a) of the TsNITA-3611 device for measuring the displacement of the body cone with a circular (b) and triangular (c) measuring tip:
1,2 - tuning screws; 3 - measuring head; 4 - hinge; 5 - measuring lever; 6 - mandrel; 7 - apiary; 8 - tip; 9 - sprayer body; 10- handle; 11- drive mechanism 3. The horizontal displacement of the lever is localized by a lamellar cross hinge 4. The diameter of the circular tip, as a rule, corresponds to the diameter of the alignment of the cones when assembling the atomizer. In this case, the conditional displacement of the cone along the center of the circle inscribed in the real profile is fixed. If the circular tip is replaced by a triangular one (see Fig. 112, c), then the value will be fixed, the average between the beat and the displacement, which gives more information about the geometry and position of the cone. Such devices, with a speed of 400 - 600 measurements per 1 hour, have a confidence error of 0.5 -0.6 μm (without taking into account the error introduced by the imposition of deviations in the shape of the base cylindrical surface on the measured parameter).
Telescopic devices are widely used to measure the angle of the conical surfaces of the atomizer (Fig. 113). The principle of measurement with such a device is based on fixing the difference H of the legs for two cone sections with known diameters (3 and /X). This method, with deviations in the surface shape, for example, non-linearity of more than 3 - 5 microns, can give a significant measurement error exceeding 15 - 30 ".
To improve the accuracy of angular measurements in the details of fuel equipment, a new method was developed at TsNITA and TsNII MPS. The method is based on comparing the geometric parameters of the cone and its position when comparing the image
1 A. s. 279065 [USSR]. A method for measuring the angle of the inner cone and the non-straightness of the generatrix of this cone. G. B. Fedotov, L. V. Segalovich and others, 17 authors in total. For-yavl. 01 - 08. 68. No. 1262056/25 - 28. Publ. in B.I., 1970, No. 26. UDC 53.083.8 (088.8).
of the longitudinal profile of the generatrix with a scale of linear and angular deviations from the profile of the standard, the role of which in measurements is played by a geometric straight line. On the basis of this method, attachments to the profilograph model 201 and stand-alone devices TsNITA-3821 and TsNII-7004 for measuring the angles and linearity of spray cones and valve pairs were manufactured.
The prefix (Fig. 114) consists of a stand 3, on which a cradle 10 is suspended in a bearing 7. Replaceable prisms 8 are installed in the traverse of the cradle, on which the measured parts are based with their precision cylindrical part. The length A of the cradle arm is calculated in such a way that the movement of the microscrew 1 by 0.01 mm gives an angular rotation of the prism by 30".
The prefix is installed on the universal table of the profilograph - profilometer and the axis of the sensor probe movement track is aligned with the vertical plane passing through the axis of the measured product. The parallelism of the generatrix of the cones of the reference and mounted products, the path of movement of the probe tip is set with a microscrew 1. The use of a standard profiler allows using the attachment to evaluate not only the angles of the cones with a relative error for a pair of no more than 2 ", but also the waviness (nonlinearity) and roughness of the generatrix.
An autonomous device (Fig. 115) consists of mechanical and electronic units. The mechanical block is designed to install the measured part and provide
Fig. 114 Scheme of the attachment to the profilograph - profilometer for measuring the angle and evaluating the profile of the forming cones of sprayers 1 - micrometric screw, 2 - spring, 3 - stand, 4 - mandrel, 5 - sprayer housing, 6 - profilograph sensor, 7 - bearing 8 - spray needle, 9 - replaceable prism, 10 - cradle for moving the measuring arm along the generatrix of the cone. The electronic unit converts the mechanical vibrations of the measuring arm into electrical signals, which are recorded on the screen of the cathode ray tube (CRT) and the tape of the recording device 9. The measuring arm 3 of the mechanical unit is connected by a backlash-free spring hinge to the guide of the movable carriage 14, which is suspended from the body of the mechanical unit on flat-spring parallelogram and receives movement from the cam mechanism 13 of the reciprocating motion; the drive of the mechanism is carried out by means of electric motors and a reducer 5. The course of the guide carriage is changed using the rocker mechanism 12.
The measured part is installed on the base mandrel 2, which has a support ring and a spherical tip for simultaneous basing on cylindrical and conical surfaces. With the help of a universal table with installation mechanism 1, moving in three planes, the generatrix of the cone is set in the measurement plane and is brought into contact with the tip of the measuring lever 3. The second end of the measuring lever, opposite to the one in contact with the measured surface, is the armature of the inductive sensor 6. The sensor is powered by voltage with a frequency of 970 Hz from the generator 7. The magnetic system is balanced using the levers and microscrews of the measuring unit 4. The electrical signal taken from the inductive sensor is fed through the measuring bridge to the amplifiers of the electronic unit 8. The amplified signal is fed to the horizontal plates of the CRT indicating device 10. Horizontal move-
Rice. 115. Schematic diagram of an autonomous device for controlling the angle and profile of the cone-forming parts of the fuel equipment, the beam on the CRT screen through the electronic unit is associated with the longitudinal movement of the movable carriage using the horizontal scanning mechanism 11, which includes a flag, an illuminator and a photoresistor. The circuit of the electronic unit was developed on the basis of the S1-19B oscilloscope.
The most important condition for the reliable and accurate operation of the considered instruments is impeccably executed standards, methods for their certification and use.
Topic: "Graphic representation of cylindrical parts."
The purpose of the lesson: - teach students to read and complete a sketch, technical drawing, drawing, show the rules for constructing drawings. Practical skill in product manufacturing. Development of skills in working with marking and cutting tools.
visual range - samples of various products of a cylindrical shape,visual aids on the image of products and their manufacture.
Safety instructions and visual aids.
Material: - pine bar.
Tool: - square, ruler, triangle, notebook, pen, pencil, eraser, caliper, planer, rasp, sandpaper.
During the classes.
Organizational part – Check readiness for the lesson.
Message about the topic of the lesson and its objectives
In technology lessons, you will make products that, along with flat rectangular parts also contain cylindrical parts. For example, handles of mallets, shovels, rakes, etc. have such a shape.
Today we will consider the drawings of cylindrical products.
We will independently mark the blanks and learn how to process them.
Repetition of the material covered
- What shapes do you know? ( prismatic, cylindrical, conical)
- What dimensions are affixed to the drawing of a prismatic part?
- What drawings are called assembly drawings?
- What is shown on the assembly drawing?
- What does the specification contain?
- What are the dimensions on the assembly drawing?
- How should an assembly drawing be read?
Presentation of new material
In the design documentation, cylindrical parts are depicted as shown in Figure 10.
Rice. 10. Technical drawing and drawing of a simple cylindrical part.
When making drawings of simple parts that have a cylindrical shape, you can limit yourself to one main view. The diameter sign Ø and the center line in the image indicate the cylindrical shape of the part. Other views are shown only if the details have elements whose shape is difficult to show in one view (Fig. 11).
Cylindrical parts (made of wood and metal) often have such structural elements as chamfers, fillets, grooves, shoulders, etc. (Fig. 12), The dimensions of the chamfer in the drawing are indicated by a record of the typeZX45°, where3-height of the chamfer (in mm),45°- corner,under which it is performed.
MANUFACTURE OF CYLINDRICAL PARTS WITH HAND TOOLS
A cylindrical part (see Fig. 10) can be made by hand. First you need to prepare a workpiece - a square bar. If you can’t pick up a finished bar of the right size, you can saw off the workpiece from the board. The dimensions of the workpiece must include an allowance for processing. The side of square A should be approximately 2 mm larger than the diameter of the part to be manufactured, and the length of the bar L - about 20 mm more than its length (Fig. 15). At both ends of the workpiece, centers are found (as the point of intersection of the diagonals) and circles are drawn corresponding to the diameter of the part.
Then, on each layer of the workpiece, two marking lines are drawn along the edges using a thickness gauge. The thickness gauge is set to a size of 2⁄7 A (Fig. 16). An octagon is marked at the ends of the workpiece (Fig. 17). The workpiece is fixed on the workbench between the wedges. The ribs are cut with a planer to the marking lines and an octahedron is obtained. Its edges without marking are cut together until a hexahedron is obtained (Fig. 18). For the final rounding, the workpiece is cleaned with a rasp, removing the remaining ribs. It is advisable to carry out this operation in the device (Fig. 19).
The part thus obtained is cleaned with sandpaper (Fig. 20).
The required length of the part is obtained by sawing with a hacksaw in the fixture (Fig. 21).
Compliance of the diameter of a cylindrical part with a given size is checkedcaliper or caliper. This is a measuring tool in the form of a compass with arcuate legs (Fig. 22, a).
It is used to compare the diameters of parts with the dimensions taken along the ruler (Fig. 22.6, c).
It is advisable to obtain short cylindrical parts (up to 100 ... 150 mm long) by sawing into parts of a long part.
When marking a bar of square section, the thickness gauge is set to a size equal to ² / 7
sides of the square.
Practical work
1. Draw students' attention to compliance with safety regulations and caution in the manufacture of the product.
2. Warn against marking errors.
3. Show the progress of work, techniques, commenting on their actions. Protect from haste, direct to thoughtful work.
Behavior of the results of the lesson, viewing work, grading.
Let's see what and how we made, mentally go through the entire technological process - what was and what has become!
Viewing works, their analysis, grading. If someone did not have time, they will finish it in the next lesson.
Lesson Summary:
In general, all the good fellows! Now we know how to make a cylindrical product from a block of wood, how to be creative in translating a drawing or sketch into a product.
In the next lesson, we will cover the basics of designing and modeling a product.
Details Mechanical engineering and material processing1. What are the requirements for cylindrical surfaces?
1. cylindricity, straightness;2. straightness generatrix, cylindricity, roundness, coaxiality;,
3. roundness, coaxiality, straightness;
2. What is a feed motion?
1. this is the movement of the cutter along the workpiece;2. this is the translational movement of the cutter, which ensures continuous cutting into new layers of metal;
3. this is the cutting surface when processing;
3. What is called the front angle?
1. angle between front and back surface;2. the angle between the front surface and the plane perpendicular to the cutting plane;
3. angle between the front surface and the cutting plane;
4. What tool is used to finish the hole?
1. drill;2. countersink;
3. sweep;
5. The class of shafts includes parts in which:
1. the length is much larger than the diameter;2. length is much less than the diameter;
3. length is equal to diameter;
6. Things to consider when using limbs:
1. the presence of lubrication;2. the number of marks on the limb;
3. the presence of backlashes;
7. What kind of thread is characterized by a triangular pitch, a profile angle of 60˚
1. metric;2. inch;
3. trapezoidal,
8. What is an allowance?
1. a layer of metal removed from the workpiece;2. a layer of metal for processing;
3. a layer of metal that is removed from the workpiece in order to obtain a part from it;
9. What is called the geometry of the cutter?
1. cutter angles;2. shape of the front surface;
3. the value of the angles of the head of the cutter and the shape of the front surface;
10. What steels are called alloyed?
1. steel smelted in electric furnaces;2. steel containing alloying elements;
3. steels smelted in open-hearth furnaces
11. Why is a three-jaw chuck called self-centering?
1. Three cams converge to the center and diverge at the same time and ensure accurate centering of the workpiece;2. basing on the outer cylindrical surface;
3. coincidence of the axis of the workpiece with the axis of rotation of the spindle;
12. How are cylindrical shank drills attached?
1. in the tailstock quill using cams;2. in the tailstock quill using a drill chuck;
3. in the tailstock quill using a template;
13. Workpieces, what parts are installed and fixed on the centers?
1. shaft blanks for fine turning;,2. shaft blanks, the length of which exceeds the diameter by 10 times;
3. shaft blanks, the length of which exceeds the diameter by 5 or more times;
14. How is the permissible overhang of the cutter from the tool holder calculated?
1. 1.2 N (cutter holders);2. 1.5 N (toolholders);
3. 1 N (cutter holders);
15. Quality is:
1. an interval of sizes that change according to a certain dependence;2. a set of tolerances corresponding to the same degree of accuracy for all nominal sizes in a given interval;
3. a list of sizes that have the same tolerance value;
16. Which of the following machine components converts the rotational movement of the lead screw into a rectilinear translational movement of the caliper?
1. guitar machine tool;2. machine apron;
3. feed box.
17. What should be the gap between the handpiece and the circle on the grinding machine:
1. no more than 6mm;2. no more than 3 mm;
3. not less than 10 mm,
18. Which of the following methods is more appropriate to obtain a conical surface (chamfer) on the cone of the rod for threading with a die:
1. by turning the upper slide of the caliper2. wide cutter;
3. displacement of the tailstock body;
19. What affects the tool life:
1. coolant quality, tool geometry;2. cutting speed;
3. tool material, workpiece material, coolant quality;
20. What surface accuracy and roughness can be obtained by drilling?
1. 5 class of accuracy, 3 roughness;2. 3 class of accuracy, 5 roughness;
3. 4 class of accuracy, 2 roughness;
21. Causes for the hole to move away from the axis of rotation:
1. end runout;2. cutting edges of various lengths;
3. displacement of the axis of centers;
22. What determines the allowance left for deployment:
1. from the diameter of the reamer;2. on the diameter of the hole, the material being processed;
3. from the processed material;
23. Cast iron - an alloy of iron with carbon, containing:
1. more than 6.67% carbon;2. more than 2.14% carbon;
3. less than 0.8% carbon;
24. How many dimensions must be indicated on the drawing for a truncated cone:
1. two;2. three;
3. four;
25. What are the shafts according to the shape of the outer surfaces:
1. stepped, oval;2. smooth, stepped;
3. smooth, conical;
26. Determine the hole tolerance Æ 40 N 7 (0.025; -0.007):
1. 0,032;2. 40,025;
3.39,075;
27. Shaft radial runout is the result?:
1. spindle runout;2. incorrect installation of the cutter;
3. wrong choice of cutting modes;
28. Brass is an alloy:
1. copper with tin;2. copper with zinc;
3. copper with chromium;
29. What elements are distinguished on the working part of the scan:
1. cutting edge, shank, intake cone;2. gauge part, cutting edge, shank;
3. cone, intake cone, gauge part;
30. Determine the angle of sharpening of the cutter, if the front cutting angle is 15, the main clearance angle is 8:
1. 67 ;2. 82 ;
3. 75 ;
31. Replacement wheels guitar is designed for:
1. to change the number of revolutions of the spindle;2. to transfer rotation to the lead screw;
3. to adjust the machine to the required feed;
32. What is the main alloying element of high speed steel:
1. chrome;2. cobalt;
3. tungsten;
33. What is the lethal current:
1. 0.1 A;2. 0.5 A;
3. 1 A;
34. What surface is used as an installation base in the manufacture of complex disks:
1. inner surface;2. outer surface;
3. outer surface, as well as ledges and recesses;
35. What is meant by the main dimensions of the machine:
1. workpiece diameter;2. overall dimensions of the machine;
3. height of centers and distance between centers;
36. What are the types of chips:
1. fracture, chipping, drain;2. fracture, chipping, deformation;
3. chipping, breaking, cutting;
37. What does the feed for threading correspond to:
1. thread pitch;2. diameter for threading;
3. thread length;
38. How much carbon is contained in U12 steel?
1. 0,12%;2. 12%;
3. 1,2%;
39. Cementation is:
1. the process of saturating steel with zinc;2. the process of saturation of steel with carbon;
3. the process of saturation of steel with carbon and nitrogen;
45. Cutting speed increases if:
1. increase feed;2. increase the spindle speed;
3. increase the depth of cut;
4. Reduce feed and increase depth of cut
46. Determine the cutting speed when turning a part with a diameter of D = 60mm and the spindle speed n = 500rpm
1. 94.2 m/min;2. 83.6 m/min;
3. 125.7 m/min;
47. In a single production, when processing shaped surfaces, the following are used:
1. processing with a cone ruler;2. processing with through cutters while using longitudinal and transverse feed;
3. processing with a copier;
48. Indicate what limits the largest possible diameter of the workpiece to be machined:
1. spindle bore diameter;2.distance from the line of centers to the bed;
3. the distance between the chuck jaws and the centers;
49. Due to what type of processing is the hardening of the surface layer of the part achieved
1. grinding;2. running, rolling, smoothing;
3. riveting;
50. How much is the deployment allowance:
1. 0.5 - 1mm per line;2. 0.08 - 0.2 mm per side;
3. 0.5 - 0.8 mm per side;
The body parts of machines are the basic parts on which most of the machine units are installed, the accuracy of the relative position of which must be ensured both in statics and during operation of the unit under load. In accordance with the foregoing, body parts must have the required accuracy, have the necessary rigidity and vibration resistance, which ensures the required relative position of the connected parts and assemblies, the correct operation of mechanisms and the absence of vibrations.
The design of body parts, the material and the required accuracy parameters are determined based on the service purpose of the parts, the requirements for the operation of mechanisms and their operating conditions. This takes into account the technological possibilities of obtaining products of a given geometry and dimensions, configuration, the possibility of machining, etc.
Machine body parts can be divided into groups (Fig. 17.1). details
Rice. 17.1. Body part groups:
a) box-type - one-piece and detachable; b) with smooth inner
cylindrical surfaces; c) a body of complex spatial shape; d) parts with guide surfaces; e) details such as brackets, squares
of these groups have a certain commonality of service purpose, which means the presence of a set of identical surfaces and an identical design in form. This, in turn, determines the features of technological solutions that ensure the achievement of the required accuracy parameters in the manufacture of parts of each group.
First group- box-shaped parts in the form of a parallelepiped, the dimensions of which are of the same order. In most cases, the main bases of such housings are flat surfaces, and the auxiliary ones are the main holes and ends intended for basing shafts and spindles.
The design and dimensions of the cases determine the conditions for placing the necessary parts and mechanisms in them. They are equipped with ribs and partitions that ensure their rigidity. With the same purpose, bosses and tides, on which the main holes are located. Box-shaped cases can be one-piece or split; the parting plane can pass along the axes of the main holes.
Second group- parts with smooth inner cylindrical surfaces, the length of which exceeds their diametrical dimensions. This group includes engine and compressor cylinder blocks, spool housings, pneumatic and hydraulic equipment, etc. In accordance with the official purpose, increased requirements are imposed on the internal cylindrical surfaces for the accuracy of diametrical dimensions and the accuracy of geometric shape. These surfaces usually wear out. Therefore, they are subject to high requirements for roughness and wear resistance.
Third group- body parts of complex spatial geometric shape. These are cases of gas and steam turbines, centrifugal pumps, collectors, tees, valves, etc.
Fourth group- body parts with guide surfaces - tables, carriages, sleds, calipers, sliders, faceplates, etc. During operation, these parts perform reciprocating or rotational movement along the guide surfaces, ensuring accurate relative movement of workpieces and tools.
Fifth group- body parts such as brackets, squares, racks, plates and covers. These parts combine the most simple in design products that act as additional supports to ensure the required accuracy of the relative position of individual mechanisms, shafts, gears.
The main bases by which housing parts are attached to beds, frames or other housings are in most cases flat surfaces or a combination of a flat surface and one or two base holes. In this case, basing schemes are most often implemented along three planes or along a plane and two holes. Auxiliary bases of body parts are the main holes, as well as flat surfaces and their combinations, which determine the position of various attached assemblies and parts - covers, flanges, etc.
Deviation from roundness- the greatest distance from the points of the real profile to the adjacent circle T roundness - the largest allowable deviation from roundness.
Roundness tolerance field- an area on a plane perpendicular to the axis of the surface of revolution or passing through the center of a sphere, bounded by two concentric circles spaced from one another at a distance equal to the roundness tolerance T.
Particular types of deviation from roundness- oval and cut.
Ovality - the real profile is an oval-shaped figure, the max or min diameters of which are in mutually perpendicular directions (running of the spindle of a lathe or grinding machine, unbalance of the part).
Cut - a real profile is a polyhedral figure with an even or odd number of faces. Occurs most often in centerless grinding - a change in the position of the instantaneous center of rotation of the part.
To determine deviations from roundness, one-, two- and three-point instruments, round gauges are used.
2. Longitudinal section.
Deviation of the profile of the longitudinal section- deviation from straightness and parallelism of the generators.
D 
differential parameters.
taper- deviation of the profile of the longitudinal section, in which the generatrices are rectilinear, but not parallel.
barrel shape- deviation of the profile of the longitudinal section, in which the generators are not straight and the diameters increase from the edges to the middle of the section.
FROM 
flatness- deviation of the profile of the longitudinal section, in which the generators are not straight and the diameters decrease from the edges to the middle of the section.
O 
cylindricity- the greatest distance from the points of the real surface to the adjacent cylinder. The concept of deviation from cylindricity characterizes the totality of deviations in the shape of the entire surface of the part.
Tolerance field - an area in space limited by two coaxial cylinders.
Deviation of the shape of flat parts.
Flatness deviations- the greatest distance from the points of the real surface to the adjacent plane within the normalized area.
Special cases- convexity, concavity.
When applying deviations from straightness and flatness, straightedges or gauge blocks are used.
There are two types of requirements for the shape of the surface:
1. The requirement for the shape of the surface in the drawing is not specified separately. In this case, it should be considered that all deviations of the surface shape in their magnitude should not exceed the size tolerance of a given element of the part.
2. The requirement for the shape of the surface is indicated on the drawing with a special sign. This means that the shape of the surface of this element must be made more accurately than its size and the amount of shape deviation will be less than the size tolerance value.
Complex parameters- parameters that impose requirements simultaneously on all types of surface shape deviations.
Private options- parameters that impose requirements on deviations that have a specific geometric shape.
In the process of processing parts, inaccuracies of the machine and elastic pressures cause random changes in dimensions, therefore, shape deviations are not pronounced (ovality, faceting, conicality, etc.), but have a complex appearance.
The profile of the machined surface is random, because the sizes of a detail in various combinations have various sizes. This difference in size is the deviation of the form.