1. What is called surface roughness?
A: Surface roughness refers to the micro-geometric features consisting of smaller pitches and peaks, and valleys on the machined surface of a part. It is a kind of micro-geometric shape error.
2. Surface roughness: How to produce?
A: The surface of the part formed by cutting or other methods, due to plastic deformation of the material in processing, mechanical vibration, friction and other reasons, there is always a geometric shape error.
3. What is the effect of surface roughness on parts?
A: surface roughness on the parts of friction and wear, fatigue strength, corrosion resistance and the nature of the fit between the parts have an important impact. 4.
4. At present, China’s “surface roughness” of the main national standards?
A: GB/T 3505 2000 surface roughness term surface and its parameters. GB/T 1031-1995 surface roughness parameters and their values. GB/T 131-1993 Mechanical Drawing surface roughness symbols, codes and their notes.
5. What is called the actual contour?
A: It is a plane and the actual surface of the intersection of the contour line. According to the different directions of intersection, it can be divided into transverse actual contour and longitudinal actual contour. In the evaluation and measurement of surface roughness, unless otherwise specified, usually according to the actual transverse contour, that is, perpendicular to the cross-section of the direction of the processing texture of the contour.
6. What is called sampling length?
A: The length of a datum line used to characterize surface roughness. The rougher the surface, the greater the sampling length should be. The sampling length is specified to limit and minimize the influence of other geometric errors on the surface roughness measurement results. In the sampling length range, generally including more than five contour peaks and contour valleys. The selected value of the sampling length is shown in GB/T 1031-1995 Surface roughness parameters and their values.
7. What is the evaluation length?
A: It is a length necessary for evaluating the profile, which may include one or several sample lengths. Due to the unevenness of the surface processing of parts, in order to fully and reasonably reflect the roughness characteristics of the surface to be measured, the need for several sampling lengths to assessed. Assessment of the length of the selected value, see GB/T 1031-1995 surface roughness parameters and their values.
8. What is called the baseline?
A: Evaluation of surface roughness parameters of the numerical size of a reference line called the baseline. There are two kinds of datum lines: the contour of the least squares line and the contour of the arithmetic mean line.
9. What is called the contour of the least squares line?
A: the contour of the least squares of the median is in the sampling length, so that the contour of each point on the contour of the square sum of the deviation of the line for the minimum.
10. What is called the contour of the arithmetic mean center line?
A: The arithmetic average of the contour of the center line is in the sampling length, the division of the actual contour for the upper and lower parts, so that the upper and lower areas are equal to the line.
11. What are the basic evaluation parameters?
A: three height parameters for the basic evaluation parameters, namely, the contour of the arithmetic mean deviation (Ra), micro-unevenness of ten points height (Rz) and the contour of the maximum height (Ry), the other three for the additional evaluation parameters, namely, the contour of micro-unevenness of the average distance (Sm), the contour of the average spacing of the single-peak (S) and the contour of the rate of the length of the support (tP).
12. What is called the contour arithmetic mean deviation (Ra)?
A: In the sampling length, the measured contour points to the contour of the median distance from the absolute value of the arithmetic mean. The Ra value is greater, the surface is rougher. Ra can objectively reflect the measured geometric characteristics of the contour. Ra value can be used to measure the motorized contour gauge, but not intuitive directly.
13. What is known as the micro-uniformity of ten points height (Rz)?
A: In the sampling length, the average of the five largest contour peak height and the average of the five largest valley depth and the larger the value of Rz, the rougher the surface. Rz is used to assess the surface roughness of the height parameter has a better intuitive, easy-to-measure value in optical instrumentation, but it reflects the geometric characteristics of the measured contour has limitations.
14. What is called the maximum height of the contour (Ry)?
A: In the sampling length, the contour of the peak line and the distance between the valley line. Peak and valley lines in the sampling length, parallel to the center line and through the contour of the highest and lowest point of the line, respectively. Parameter Ry, measurement is simple, when the measured surface is very small, not suitable for Rz, Rz evaluation, can be used for Ry.
15. Surface roughness height assessment parameters (Ra, Rz, Ry): How to determine the permissible value?
A: See GB/T 1031-1995 surface roughness parameters and their values.
16. Surface roughness of the symbol, the code for 
, what is its meaning?
A: The basic symbols indicate that the surface can be obtained by any method. When no roughness parameter values or relevant instructions (eg, surface treatment, local heat treatment conditions, etc.) are added, it only applies to simplify the code labeling.
17. Surface roughness of the symbol, code for 
, what is its significance?
A: The basic symbol plus a short stroke, indicating that the surface is obtained by removing the material. For example: turning, milling, drilling, grinding, shearing, polishing, corrosion, EDM, gas cutting and so on.
18. Surface roughness of the symbol, code for 
, what is its significance?
A: The basic symbol plus a small circle, indicating that the surface is obtained by methods that do not remove the material. For example: casting, forging, stamping deformation, hot rolling, cold rolling, powder metallurgy and so on. Or it is used to maintain the original supply condition of the surface (including maintaining the condition of the previous process).
19. Surface roughness of the symbol, code for 
, what is its significance?
A: The upper limit of Ra is 3.2μm for the surface roughness obtained by any method.
20. Surface roughness of the symbol, code for 
, what is its meaning?
A: The surface roughness obtained by the method of removing material, Ra’s upper limit value is 3.2μm.
21. Surface roughness of the symbol, code for 
, what is its meaning?
A: The surface roughness obtained by the method of not removing material, Ra’s upper limit value is 3.2μm.
22. Surface roughness of the symbol, code for 
, what is its meaning?
A: The surface roughness obtained by the method of material removal, Ra’s upper limit value is 3.2μm, Ra’s lower limit value is 1.6μm.
23. Surface roughness of the symbol, code for 
, what is its meaning?
A: The surface roughness obtained by any method, the upper limit value of Ry is 3.2μm.
24. Surface roughness of the symbol, code for 
, what is its meaning?
A: The surface roughness obtained by the method of not removing material, the upper limit value of Rz is 200μm.
25. Surface roughness of the symbol, code for 
, what is its meaning?
A: The surface roughness obtained by the method of removing material, the upper limit value of Rz is 3.2μm, and the lower limit value of Rz is 1.6μm.
26. Surface roughness of the symbol, code for
, what is its meaning?
A: The surface roughness obtained by the method of removing material, the upper limit value of Ry is 3.2μm, and the lower limit value of Ry is 12.5μm.
27. What should be noted when labeling surface roughness?
A: height parameter selection Ra, the labeling can be omitted from its code, the selection of Ry, Rz, the code can not be omitted. Drawings given on the surface roughness code are the completion of the surface requirements, generally only need to note the symbols and parameters that can be allowed. Suppose the surface function of the part has special requirements (processing texture, machining allowance and other additional requirements). In that case, it can be marked around the basic symbols of the relevant parameters or generation (symbols).
28. How to draw the surface roughness symbol?
A: As shown in Figure 1.
d’ = h/10 H = 1.4h h is font height.
29. What are the surface roughness labeling methods? Example 1.
A. As shown in Figure 2.
The surface roughness surrogate (symbol) shall be noted on visible contour lines, dimension lines, dimension boundaries, or their extensions. The tip of the symbol must point from outside the material to the surface.
30. What are the surface roughness labeling methods? Example 2.
A. As shown in Figure 3.
Center hole work surface, keyway work surface, chamfering, rounded surfaces, you can simplify the labeling.
31. What are the surface roughness labeling methods? Example 3.
A: As shown in Figure 4.
Gears, involute splines, threads and other work surfaces are not drawn when the tooth (tooth) shape of the labeling method.
32. Surface roughness labeling methods? Example 4.
A: As shown in Figure 5.
The same surface has different surface roughness requirements, must be drawn with a thin solid line of the demarcation line, and note the corresponding surface roughness of the symbols and dimensions.
33. Surface roughness labeling methods? Example 5.
A: As shown in Figure 6.
Need to indicate the local heat treatment or local plating and coating, should be drawn with a thick dotted line and labeled with the corresponding size of the range, but also can be written in the requirements of the surface roughness symbols.
34. Surface roughness labeling methods? Example 6.
A: As shown in Figure 7.
Parts of continuous surfaces and repeated elements (holes, grooves, teeth …… etc.) of the surface and with a fine solid line connection discontinuous a surface, its generation (symbols) marked only once.
35. surface roughness labeling methods? Example 7.
A: As shown in Figure 8.
Most of the surface of the parts require the same, in the upper right corner of the uniform labeling, and add the word “the rest”. In order to simplify the labeling, or location restrictions, can be marked to simplify the code, you can also use the omitted method, but it must be near the title bar to explain the meaning of this simplified code (symbol). The use of uniform labeling and simplified labeling, their code and text description should be on other surfaces of the graph of the code and text 1.4 times.
36. Surface roughness parameters and the provisions of the position of the note, how to provide?
A: As shown in Figure 9.
37. How to choose the surface roughness?
A: The choice of surface roughness should not only meet the functional requirements of the use of the surface of the part, but also consider the economy of processing.
38. Determine the surface roughness by analogy. The height parameters are generally selected according to which principles?
A: On the same part, the surface roughness value of the working surface should be less than the non-working surface. The surface roughness value of the friction surface should be less than the non-friction surface, the rolling friction surface’s surface roughness value should be less than the sliding friction surface, at high speeds of movement, the unit pressure surface roughness value should be small. The surface of the cyclic load and easy to cause stress concentration (such as rounded corners, grooves) surface roughness value should be selected smaller. With the nature of the combination of high requirements of the surface, with a small gap with the surface and the requirements of a reliable connection, subject to heavy loads, such as the surface of the interference fit, should take a smaller surface roughness value. With the same nature, the smaller the size of the part, the smaller the surface roughness value should be. The same level of accuracy, small size than large size, the shaft is smaller than the hole surface roughness value. For the surface, its size tolerance, shape tolerance, and surface roughness should, in general, there is a certain correspondence.
39. Surface roughness Ra for 50 ~ 100μm, the surface shape of what features, and how to apply?
A: The surface shape is characterized by clearly visible knife marks, applied to the rough machining surface, generally rarely used. Casting, forging, and gas cutting blanks up to this requirement.
40. Surface roughness Ra for 25μm, the surface shape of what features, and how to apply?
A: The surface shape is characterized by visible knife marks, applied to the rough machining surface, generally rarely used. Casting, forging, and gas cutting blanks up to this requirement.
41. Surface roughness Ra 12.5μm, the surface shape of what features, and how to apply?
A: The surface shape is characterized by microscopic cutter marks, applied to the rough machining surface is more accurate at the first level, a wider range of applications, such as shaft end face, chamfer, screw holes and rivet holes in the surface, the contact surface of the washer, and so on.
42. Surface roughness Ra for 6.3μm, the surface shape of what features, and how to apply?
A: The surface shape is characterized by visible machining marks, applied to semi-rough machining surfaces, non-contacting free surfaces such as brackets, boxes, clutches, pulley sides, cam sides, etc., surfaces in contact with bolt heads and rivet heads, receding grooves of all shafts and holes, and the bonding surfaces of general masking plates.
43. When the surface roughness Ra is 3.2μm, what are the characteristics of the surface shape, and how can they?
A: The surface shape is characterized by the slightest trace of machining, used in semi-finishing surface, box, bracket, cover, sleeve and other parts connected to other parts without the matching requirements of the surface, the need for blue surface, the need for knurling pre-machined surfaces, non-contact spindle all the external surfaces. Turning and other basic cutting methods are used to achieve a more economical surface roughness value.
44. Surface roughness Ra for 1.6μm, the surface shape characteristics, and how to apply?
A: The surface shape is characterized by the inability to see the machining traces, applied to the surface of the surface quality requirements of high, medium-sized machine tool table (general accuracy), combined machine tool spindle box and the cover surface of the combination of the surface of the medium-sized flat belt pulleys and triangular belt pulleys, the bushing sliding bearings pressed into the hole, the general rotation of the low-speed journals. Aviation, aerospace products, and some important parts of the non-coordinated surface.
45. Surface roughness Ra for 0.8μm, the surface shape of what characteristics, and how to apply?
A: The surface shape is characterized by the direction of discernible machining traces, used in medium-sized machine tools (general precision) sliding guide surface, guide plate, cylindrical pin and taper pin surface, general precision dials, need to be chrome-plated and polished external surface, medium-speed rotation of the journal, positioning pins pressed into the hole and so on. It is a common value with the surface, medium and heavy equipment, important in the place, grinding processing economy.
46. Surface roughness Ra for 0.4μm, the surface shape of what characteristics, and how to apply?
A: The surface shape characteristics for the direction of the micro-discrimination machining traces, applied to medium-sized machine tools (to improve accuracy) sliding guide surface, the working surface of the slide bearing, fixture positioning elements and the main surface of the drill bush, crankshaft and camshaft work journals, indexing plate surface, high-speed work under the journal and the working surface of the bushing, etc..
47. When the surface roughness Ra is 0.2μm, what are the characteristics of the surface shape, and how can they be?
A: The surface shape is characterized by the direction of indistinguishable processing traces, used in precision machine tools spindle taper hole, the top taper surface, small diameter precision mandrels and shafts of the combination of surfaces, piston piston pin holes, the requirements of airtight surfaces and support surfaces, aviation engine blades leaf pots and the back of the leaf.
48. Surface roughness Ra for 0.1μm, the surface shape of what characteristics, and how to apply?
A: The surface shape is characterized by a dark glossy surface, applied to precision machine tool spindle box and sleeve with the hole, the instrument in use to bear the friction of the surface, such as rails, groove surface, etc., the surface of the hole for hydraulic transmission, the valve’s working surface, the inner surface of the cylinder, the surface of the piston pin and so on. General mechanical design boundary values. Grinding is very uneconomical.
49. Surface roughness Ra for 0.05μm, the surface shape of what characteristics, and how to apply?
A: The surface shape is characterized by a bright, glossy surface, used in special precision rolling bearing raceway, ball and roller surface, gauge in an intermediate precision clearance with the surface of the parts, the measuring surface of the gauge, and so on.
50. Surface roughness Ra for 0.025μm, the surface shape of what characteristics, and how to apply?
A: The surface shape is characterized by a mirror-like glossy surface, which is applied to the raceway, ball and roller surfaces of special precision rolling bearings, the mating surfaces of the plunger and plunger sleeve in high-pressure oil pumps, and the bonding surfaces to ensure a high degree of airtightness.
51. Surface roughness Ra for 0.012μm, the surface shape of what characteristics, and how to apply?
A: The surface shape is characterized by a matte mirror, applied to the measuring surface of the instrument, the working surface of the high precision clearance parts in the gauge, and a size of more than 100mm of the working surface of the gauge block.
52. Surface roughness Ra for 0.008μm, the surface shape of what characteristics, and how to apply?
A: The surface shape is characterized by a mirror, which is applied to the working surface of measuring blocks, the measuring surface of high-precision measuring instruments, and the metal mirror surface of optical measuring instruments.
53. When the surface roughness Ra is >10~40μm, what are the economic processing methods?
A: Economic processing methods for rough turning, rough planing, rough milling, drilling, burr filing, and sawing.
54. When the surface roughness Ra is >5~10μm, what are the economic processing methods?
A: economic processing methods for turning, planing, milling, boring, drilling, and rough reaming.
55. Surface roughness Ra> 2.5 ~ 5μm, the economic processing methods for which?
A: economic processing methods for turning, planing, milling, boring, grinding, pulling, rough scraping, and rolling.
56. Surface roughness Ra> 1.25 ~ 2.5μm, the economic processing methods for which?
A: economic processing methods for turning, planing, milling, boring, grinding, pulling, scraping, pressing, milling teeth.
57. Surface roughness Ra> 0.63 ~ 1.25μm, the economic processing methods for which?
A: economic processing methods for turning, boring, grinding, pulling, scraping, reaming, grinding rolling.
58. Surface roughness Ra> 0.32 ~ 0.63μm, the economic processing methods for which?
A: Economic processing methods for fine reaming, fine boring, grinding, scraping, and rolling.
59. Surface roughness Ra> 0.16 ~ 0.32μm, economic processing methods for which?
A: economic processing methods for grinding, honing, grinding ultra-finishing.
60. Surface roughness Ra> 0.08 ~ 0.16μm, the economic processing methods for which?
A: Economic processing methods for fine grinding, grinding, and ordinary polishing.
61. Surface roughness Ra> 0.01-0.08μm, the economic processing methods for which?
A: Economic processing methods for ultra-fine grinding, fine polishing, and mirror grinding.
62. Surface roughness Ra is ≤ 0.01μm, the economic processing methods for which?
A: The economic processing method is mirror grinding, ultra-fine grinding.
63. Thread surface roughness parameter value Ra how to choose?
A: Ra is 0.4~0.8μm when the accuracy grade of coarse thread is 4.
Ra is 0.8μm when the accuracy grade of coarse thread is 5.
Ra is 1.6~3.2μm when the accuracy grade of coarse thread is 6.
Ra is 0.2~0.4μm when the accuracy grade of fine thread is 4.
Ra is 0.8μm when the accuracy grade of fine thread is 5. Ra is 0.8μm when the accuracy grade of fine thread is 5. 0.8μm.
Ra is 1.6~3.2μm for fine thread common thread accuracy class 6.
64. How to choose the surface roughness parameter Ra for the key bond?
A: Ra is 0.2~0.5μm when the bond is in the form of a key, moving along the hub groove.
Ra is 0.2~0.4μm when the bond is in the form of a key, moving along the shaft groove.
Ra is 1.6μm when the bond is in the form of a key, moving along the hub groove.
Ra is 1.6μm when the bond is in the form of a shaft groove, moving along the hub groove.
Ra is 0.4~0.8μm when the bond is in the form of a shaft groove, moving along the hub groove.
Ra is 0.4~0.8μm when the bond is in the form of a key, moving along the hub groove. Ra is 0.4~0.8μm when the bond is in the form of a key, moving along the hub groove. The Ra is 1.6μm for the combined form of the shaft groove and immovable.
The Ra is 0.4~0.8μm for the combined form of the hub groove and moving along the hub groove.
The Ra is 1.0μm for the combined form of the hub groove and moving along the shaft groove.
The Ra is 1.6~3.2μm for the combined form of hub groove and immovable.
Note: The Ra of the non-working surfaces is all 6.3μm.
65. How to choose the surface roughness parameter Ra for a rectangular spline?
A: Inner spline, outer diameter, Ra is 6.3μm.
Inner spline, inner diameter, Ra is 0.8μm.
Inner spline, key side, Ra is 3.2μm.
Outer spline, outer diameter, Ra is 3.2μm.
Outer spline, inner diameter, Ra is 0.8μm.
Outer spline, key side, Ra is 0.8μm.
66. How to choose the gear surface roughness parameter Ra?
A: Ra is 0.2~0.4μm when the part of the gear surface accuracy grade 5.
Ra is 0.4μm when the part of the gear surface accuracy grade 6.
Ra is 0.4~0.8μm when the part of the gear surface accuracy grade 7.
Ra is 1.6μm when the part of the gear surface accuracy grade of 8.
Ra is 3.2μm when the part of the gear surface accuracy grade 9.
Ra is 6.3μm when the part of the gear surface accuracy grade of 10. Ra is 6.3 μm when the accuracy class is 10.
Ra is 0.8~1.6 μm when the accuracy class is 5.
Ra is 1.6~3.2 μm when the accuracy class is 6.
Ra is 1.6~3.2 μm when the accuracy class is 7.
Ra is 1.6~3.2 μm when the accuracy class is 8.
Ra is 1.6~3.2 μm when the accuracy class is 9. Ra is 1.6~3.2 μm when the accuracy class is 9. Ra is 3.2~6.3 μm for external circle accuracy grade 9.
Ra is 3.2~6.3 μm for external circle accuracy grade 10.
Ra is 0.4~0.8 μm for endface accuracy grade 5.
Ra is 0.4~0.8 μm for endface accuracy grade 6.
Ra is 0.8~3.2 μm for endface accuracy grade 7. Ra is 0.8~3.2 μm for endface accuracy grade 6. Ra is 0.8~3.2 μm for endface accuracy grade 8. Ra is 0.8~3.2 μm for endface accuracy grade 7. For endface accuracy class 8, Ra is 0.8~3.2 μm.
For endface accuracy class 9, Ra is 3.2~6.3 μm.
For endface accuracy class 10, Ra is 3.2~6.3 μm.
67. How to choose the surface roughness parameter Ra of a worm gear?
A: Ra is 0.2μm when the worm part is the tooth surface accuracy grade of 5.
Ra is 0.4μm when the worm part is the tooth surface accuracy grade of 6.
Ra is 0.4μm when the worm part is the tooth surface accuracy grade of 7.
Ra is 0.8μm when the worm part is the tooth surface accuracy grade of 8.
Ra is 1.6μm when the worm part is the tooth surface accuracy grade of 9.
worm Ra is 0.2μm when the accuracy grade of the top of the tooth is 5.
Ra is 0.4μm when the accuracy grade of the top of the tooth is 6.
Ra is 0.4μm when the accuracy grade of the top of the tooth is 7.
Ra is 0.8μm when the accuracy grade of the top of the worm is 8.
Ra is 1.6μm when the accuracy grade of the top of the worm is 9.
Note: When the part of the worm is the Note: Ra is 6.3 μm for all worm shaft parts.
Ra is 0.4 μm for the worm gear part with gear face accuracy class 5.
Ra is 0.4 μm for the worm gear part with gear face accuracy class 6.
Ra is 0.8 μm for the worm gear part with gear face accuracy class 7.
Ra is 1.6 μm for the worm gear part with gear face accuracy class 8.
Ra is 3.2 μm for the worm gear part with gear face accuracy class 9. Ra is 3.2 μm.
Note: Ra is 3.2 μm for the worm gear part of the tooth root.
68. How to choose the surface roughness parameter Ra of the sprocket wheel?
A: Ra is 1.6~3.2μm when the working surface accuracy of the teeth is general.
Ra is 0.8~1.6μm when the working surface accuracy of the teeth is high.
Ra is 3.2μm when the accuracy of the bottom of the teeth is general.
Ra is 1.6μm when the accuracy of the bottom of the teeth is high.
Ra is 1.6~3.2μm when the accuracy of the top of the teeth is general.
Ra is 1.6~6.2μm when the accuracy of the top of the teeth is high. Ra is 1.6 to 6.3 μm for high accuracy top of the tooth.
69. How to choose the surface roughness parameter Ra of the pulley?
A: Part of the working surface of the pulley, pulley diameter ≤ 120mm, Ra 0.8μm.
Part of the working surface of the pulley, pulley diameter ≤ 300mm, Ra 1.6μm.
Part of the working surface of the pulley pulley pulley diameter > 300mm, Ra 3.2μm.
70. Hydraulic components surface roughness parameter value Ra: How to choose?
A: Part of the piston pump crank, piston, Ra 1.6 ~ 0.8μm.
Part of the connecting rod journal, shaft tile, center journal, Ra 0.4μm.
Part of the piston outer column surface, side surface, Ra 0.8μm.
Part of the piston pump connecting rod holes, cylinder cylinder, slide valve liner, plunger, piston, Ra 0.8 ~ 0.4μm.
Part of the slide valve, the high-pressure pump piston valve, the valve seat, Ra 0.8 ~ 0.4μm. Part of the slide valve, high-pressure pump ram, valve seat, Ra 0.8 ~ 0.4μm. Valve seat, Ra is 0.2~0.1μm.
71. How to choose the surface roughness parameter Ra for the mating surfaces of plain bearings?
A: For shaft tolerance class IT7-IT9, Ra is 0.2~3.2μm.
For shaft tolerance class IT11-IT12, Ra is 1.6~3.2μm.
For the hole tolerance class IT7-IT9, Ra is 0.4~1.6μm.
For the hole tolerance class IT11-IT12, Ra is 1.6~3.2μm.
72. How to choose the surface roughness parameter Ra of a conical bond?
A: The part is the sealing joint of the outer conical surface, Ra is ≤0.1μm.
The part is the centering joint of the outer conical surface, Ra is ≤0.2μm.
The part is the other joints of the outer conical surface, Ra is ≤1.6-3.2μm.
The part is the sealing joint of the inner conical surface, Ra is ≤0.2μm.
The part is the centering joint of the inner conical surface, Ra is ≤0.8μm.
The part is the other joints of the inner conical surface, Ra is ≤1.6-3.2μm. The part is the other joints of the inner conical surface, Ra is ≤0.2μm. For other joints on the inner conical surface, Ra is ≤1.6~3.2μm.
73. What are the labeling methods for surface roughness? Specification 1.
A: The direction of numbers and symbols in the surface roughness code must be labeled according to the following figure. As shown in Figure 10.
74. What are the methods of labeling surface roughness? Specification 2.
A. Surface roughness symbols with horizontal lines should be labeled as shown below. See Figure 11 shown.
75. What are the methods of labeling surface roughness? Specification 3.
A: The tip of the symbol must point to the surface from the outside of the material, the use of the most of a roughness code unified in the upper right corner of the drawing, preceded by “others” two words. As shown in Figure 12.
76. What are the methods of labeling surface roughness? Specification 4.
A: When all surface roughness requirements are the same, it can be uniformly noted in the upper right corner of the drawing. As shown in Figure 13.
77. What are the methods of labeling surface roughness? Specification 5.
A: When there are different surface roughness requirements on the same surface, the dividing line shall be drawn with a fine solid line. As shown in Figure 14.
78. What are the methods of labeling surface roughness? Specification 6.
A: The surface roughness designation of continuous surfaces and surfaces with repeating elements (holes, slots, teeth, etc.) and discontinuous surfaces connected by fine solid lines is labeled only once. As shown in Figure 15.
79. What are the methods of labeling surface roughness? Specification 7.
A: When the place is narrow or inconvenient to label, the code can lead to labeling. As shown in Figure 16.
80. What are the methods of labeling surface roughness? Specification 8.
A: To simplify the labeling or labeling position is restricted, you can mark the simplified code, can also be used to omit the note method (see below), but should be near the title bar to explain the meaning of the simplified code. Figure 17 shows.
81. What are the methods of labeling surface roughness? Specification 9.
A: need to be parts of local heat treatment or plating (coating), should be a thick dotted line to draw the range and mark the corresponding size, but also can be written in the requirements of the surface roughness symbols. As shown in Figure 18.
82. What are the methods of labeling surface roughness? Specification 10.
A: The surface roughness designation of the working surface of the center hole, the working surface of the keyway, the chamfer, and the fillet can be simplified and marked according to the following figure. As shown in Figure 19.
83. What are the methods of labeling surface roughness? Specification 11.
A: When gears, involute splines, threads and other working surfaces do not have drawn tooth (tooth) shapes, their surface roughness designations can be labeled in the following manner. As shown in Figure 20.
84. Surface roughness of the other labeling code for 
, what is its significance?
A: Sampling length should be labeled in the symbol of the long side of the horizontal line below the sampling length I = 2.5mm.
85. Surface roughness of the other labeling code for 
, what is its significance?
A: Roughness requirements by the specified processing methods can be labeled with text in the symbol of the long side of the horizontal line above.
86. Surface roughness of the other labeling code for 
, what is its significance?
A: The need to control the surface processing texture direction can be added to the right side of the symbol of the texture direction.
87. Surface roughness of the other labeling code for 
, what is its significance?
A: The Machining allowance should be marked on the left side of the symbol, indicating a machining allowance of 2mm.
88. Surface roughness of the other labeling code for 
, what is its significance?
A: The surface roughness value of the plating (coating) before the labeling.
89. Surface roughness of the other labeling code for 
, what is its significance?
A: It indicates the labeling of surface roughness after plating (coating) or other surface treatment.
90. What various functions are affected by the choice of surface roughness?
A: Surface roughness on a variety of functions: such as coefficient of friction, wear, fatigue strength, impact strength, corrosion resistance, contact stiffness and vibration resistance, clearance in the gap fit, interference fit in the bonding strength, measurement accuracy, thermal conductivity, electrical conductivity and contact resistance, sealing, bonding strength, paint performance, plating quality, resistance to fluid flow, the reflective properties of light, food hygiene, appearance, Quality of sprayed metal, lubrication during stamping of steel plates, etc.
91. What is the effect of the choice of surface roughness on the nature of the fit?
A: Affects the reliability and stability of the performance of the fit. For a clearance fit, due to initial wear, the peak will soon wear away, so that the gap increases, for an overfill fit, assembly press fit, will also be squeezed wave peaks, reducing the actual effective interference, especially for small sizes with a more significant impact. Therefore, with the nature of the high stability requirements of the bonding surface, dynamic fit with a small gap surface, the requirements of the connection is firm and reliable, bear the load of large static fit Ra value should be low, the same tolerance level of small size than large size (especially 1 ~ 3 tolerance level), the same tolerance level of the shaft than the hole !” Value to be smaller, and with the same nature of the fit, the smaller the size of the part, the smaller its Ra value.
92. What is the impact of the choice of surface roughness on wear resistance?
A: The surface of the machined part, due to the existence of peaks and valleys, so in a contact surface where that is just some peak contact, thus reducing the contact area, and the specific pressure increases, wear increases. Therefore, friction surfaces than non-friction surfaces, rolling friction surfaces than sliding friction surfaces with high speed of movement, unit pressure of the friction surface Ra value is smaller.
93. What is the effect of the choice of surface roughness on the contact stiffness?
A: When the two surfaces are in contact, because the actual contact area is a part of the ideal contact area, the unit area of compressive stress increases, and when subjected to external forces, easy to produce contact deformation. Therefore, reducing the Ra value can improve the contact stiffness of the bond.
94. What is the effect of the choice of surface roughness on fatigue strength?
A: The rougher the surface of the part, the more sensitive to stress concentration, resulting in fatigue damage to the part. Therefore, the surface subject to cyclic loading and easy to cause stress concentration of the part, such as rounded corners, grooves, at a Ra value should is low. Surface roughness on the fatigue strength of the parts of a degree of influence on its material is different. The impact of cast iron is not very obvious, for the steel parts of the strength of the greater the impact of the stronger they are.
95. What is the impact of the choice of surface roughness on the impact strength?
A: The impact strength of the steel surface with the reduction of surface roughness Ra value improves, especially in the low temperature condition, especially obvious.
96. What is the impact of the choice of surface roughness on the measurement accuracy?
A: As the surface of the workpiece has microscopic unevenness, measurement, the measuring rod actually contacts the peaks, although the measurement force is not large, but the contact area is small, the force per unit area is not small, so it causes a certain contact deformation. As the surface micro-unevenness has certain peaks and valleys, such as the measurement, the measuring head, and the measured surface to be made between the relative sliding, which makes the measuring rod also measure the peaks and valleys of the surface up and down fluctuations, the impact of fluctuations in the display value also has fluctuations.
97. What is the impact of the choice of surface roughness on the sealing?
A: No relative sliding static sealing surface, a microscopic unevenness valley is too deep, so that the pre-pressurized sealing material can not be filled, leaving a gap, resulting in leakage. The rougher the surface, the more leakage. Relative sliding dynamic sealing surface, due to the relative movement, its microscopic unevenness is generally 4~5μm, for the storage of lubricants is more favorable, as the surface is too smooth, not only is it not conducive to the storage of lubricants, but also causes friction and wear. In addition, the sealing is also related to the direction of the processing texture.
98. What is the impact of the choice of surface roughness on corrosion resistance?
A: surface roughness of corrosive gases or liquids on the surface of the part is easy to accumulate, and on the surface layer of the part, exacerbating corrosion. Therefore, in the corrosive gases or liquids under the conditions of the surface of the parts to be small Ra value is required.
99. What is the impact of the choice of surface roughness on the quality of metal surface coating?
A: After the workpiece is galvanized, chromium, copper, the depth of its surface microscopic unevenness is doubled than before plating, while after nickel plating, it will be reduced by half than before plating. And because the rough surface can absorb the tensile stress generated by the cooling of the sprayed metal layer, it is not easy to produce cracks. Before the spraying of metal before the surface must be made to have a certain degree of roughness.
100. What is the impact of the choice of surface roughness on vibration and noise?
A: mechanical equipment, the surface roughness of the moving parts, and operation will produce vibration and noise, especially high-speed rolling bearings, gears and engine crankshafts, camshafts and other parts. This phenomenon is more obvious. Therefore, the smaller the surface roughness Ra value of the moving parts, the smoother and noisier the moving parts.
