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This post was last edited by 3968668 on 2011-7-25 at 21:39. Tolerances for shape and position (excerpted from GB1182－84－80). Symbols for form and position tolerances; Classification: Shape tolerances, Position tolerances. Items include straightness, flatness, roundness, cylindricity, parallelism, perpendicularity, inclination, coaxiality, symmetry, positional accuracy, circular runout, total runout. Symbols: http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image001.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image002.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image003.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image004.gif http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image005.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image006.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image007.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image008.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image009.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image010.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image011.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image012.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image013.jpg. Tolerances for roundness and cylindricity in μm; Legend for the primary parameter d(D): http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image014.jpg. Tolerance grades; Primary parameter d(D) in mm; Examples of applications: >6～10, >10～18, >18～30, >30～50, >50～80, >80～120, >120～180, >180～250, >250～315, >315～400, >400～500. 5, 1.5, 2, 2.5, 2.5, 3, 4, 5, 7, 8, 9, 10. Fit surfaces for E and C grade rolling bearings, shaft journals in general reducers, and spindles in ordinary machine tools. 6 2.5 3 4 4 5 6 8 10 12 13 15 7 4 5 6 7 8 10 12 14 16 18 20 Pistons of jacks or hydraulic cylinders; journals of water pumps and reducers; distribution mechanisms in hydraulic drive systems. 8 6 8 9 11 13 15 18 20 23 25 27 9 9 11 13 16 19 22 25 29 32 36 40 Sliding bearings used in cranes and winches, etc. 10 15 18 21 25 30 35 40 46 52 57 63 Tolerances for straightness and flatness, in μm. Main parameter L. Illustration: http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image015.jpg Tolerance classes; main parameter L in mm; application examples: ≤10, >10–16, >16–25, >25–40, >40–63, >63–100, >100–160, >160–250, >250–400, >400–630. 5 2 2.5 3 4 5 6 8 10 12 15 Machine tool guides with ordinary precision. 6 3 4 5 6 8 10 12 15 20 25 7 5 6 8 10 12 15 20 25 30 40 Support surfaces of bearing housings; housing of reducers; mating surfaces of shaft support bearings. 8 8 10 12 15 20 25 30 40 50 60 9 12 15 20 25 30 40 50 60 80 100 Support surfaces of auxiliary mechanisms and manual machinery; connecting surfaces of hydraulic fittings and flanges. 10 20 25 30 40 50 60 80 100 120 150 Tolerances for parallelism, perpendicularity, and angularity, in μm. Main parameters L, d (D). Illustration: http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image016.jpg Tolerance classes; main parameters L, d (D) in mm; application examples: ≤10, >10–16, >16–25, >25–40, >40–63, >63–100, >100–160, >160–250, >250–400, >400–630. 5 5 6 8 10 12 15 20 25 30 40 Perpendicularity applies to the shafts of engines and flanges of clutches; shoulders on housings fitted with D- and E-grade bearings as well as C- and D-grade bearings. 6 8 10 12 15 20 25 30 40 50 60 Parallelism applies to working surfaces of drilling jigs with medium precision; centerlines of holes in gearbox housings with precision levels 7–10. 7 12 15 20 25 30 40 50 60 80 100 Perpendicularity applies to the axes of holes in housings fitted with F- and G-grade bearings; centerlines of holes in conical-shaft reducers connected via h6 and g6 fits. 8 20 25 30 40 50 60 80 100 120 150 Parallelism applies to end faces of bearing caps in heavy machinery; drive shafts in manual transmission systems. Tolerances for coaxiality, symmetry, circular runout, and total runout, in μm. Main parameters d(D), B, L. Illustration: http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image017.jpg Tolerance classes; main parameters d (D), B, L in mm; application examples: >3–6, >6–10, >10–18, >18–30, >30–50, >50–120, >120–250, >250–500. 5 3 4 5 6 8 10 12 15 Mating surfaces of gear shafts with precision levels 6 and 7; high-precision fast-running shafts; shaft sleeves for machine tools with higher precision. 6 5 6 8 10 12 15 20 25 7 8 10 12 15 20 25 30 40 Mating surfaces of gear shafts with precision levels 8 and 9; high-speed shafts with ordinary precision (below 100 r/min); main drive shafts less than 1 m in length; mating holes of drums and rolling surfaces of guide wheels in lifting and transport equipment. M 12 15 20 25 30 40 50 60 Surface roughness. Application ranges of Ra values for surface roughness; roughness codes; finish codes; surface shapes and characteristics; processing methods; application ranges. Ⅰ Ⅱ Illustration: http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image018.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image019.jpg Burrs removed; surfaces maintained in their original supplied condition after casting, forging, stamping, hot rolling, or cold rolling. Illustration: http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image020.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image021.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image022.jpg Slight tool marks visible; surfaces after rough turning, planing, vertical milling, face milling, or drilling. Illustration: http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image023.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image024.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image025.jpg Processing traces clearly visible; relatively precise rough-machined surfaces such as turned end faces and chamfers. Illustration: http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image026.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image027.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image028.jpg Processing traces barely noticeable; non-mating surfaces of unimportant parts such as end faces and chamfers of shafts and covers; side surfaces of gears and pulleys; upper and lower surfaces of flat keys and keyways; relief grooves on shafts or holes. Illustration: http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image029.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image030.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image031.jpg No processing traces visible; mating surfaces of parts with IT12 tolerance level such as covers, sleeves, etc., which are joined to other parts but do not form a fit; non-working surfaces of gears; working surfaces of keys and keyways; friction surfaces between shafts and felt rings. Illustration: http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image032.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image033.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image034.jpg Direction of processing traces discernible; mating surfaces of parts with IT8–IT12 tolerance levels such as working surfaces of pulleys; tooth surfaces of gears with ordinary precision; holes in housings mated with low-precision rolling bearings. Illustration: http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image035.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image036.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image037.jpg Direction of processing traces barely discernible; mating surfaces of parts with IT6–IT8 tolerance levels ； Fit surfaces with gears, worm gears, sleeves, etc ； Shaft journal paired with high-precision rolling bearings ； Working surfaces of gears with grade 7 precision ； Working surface of the sliding bearing bushing ； Tooth surfaces of worms with 7–8 grade precision: http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image038.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image039.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image040.jpg. It is not possible to determine the direction of the machining marks. Grinding, lapping, superfinishing; mating surfaces of parts with IT5 and IT6 tolerances, as well as shaft journals used in conjunction with rolling bearings of C grade precision ； Working surfaces of gears with precision grades 3, 4, and 5: http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image039.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image041.jpg http://www.mapeng.net/Files/UpLoadfiles/20101111liu/match.files/image042.jpg Darkly glossy surface; super-machining; surfaces of machine guides ； Working surface of hydraulic drive that requires sealing ； Outer surface of the plug ； Inner surface of the working cylinder. Note: 1. The roughness code I represents the first type of transition. It takes the value from the first series of the next closest grade in the new national standard; for example, if the original surface finish rating (under the old standard) is ▽5, then the maximum allowable value for Ra is 6.3. Therefore, without affecting the original surface roughness requirements, using this value is beneficial for processing. 2. The roughness code II represents the second type of transition method. It takes the value from the first series of the nearest higher grade specified in the new national standard; for example, if the original surface finish is ▽5, the maximum allowable value for Ra is 3.2. Therefore, using this value increases the requirements for the original surface roughness as well as the processing cost.