Standard tolerance level table
GB/T1804-2000 Limit deviation values of linear dimensions
Basic size segments
0.5-3 >3-6 >6-30 >30-120 >120-400 >400-1000 >1000～2000 >2000～4000
Precision f ±0.05 ±0.1 ±0.15 ±0.2 ±0.3 ±0.5
Medium m ±0.1 ±0.2 ±0.3 ±0.5 ±0.8 ±1.2 ±2
Rough c ±0.2 ±0.3 ±0.5 ±0.8 ±1.2 ±2 ±3 ±4
Coarsest v ±0.5 ±1 ±1.5 ±2.5 ±4 ±6 ±8
(GB/T1804-2000) Limit deviation values of chamfering radius and chamfering height dimensions
Basic size segments
0.5～3 >3～6 >6～30 >. 30
Precision f ±0.2 ±0.5 ±1 ±2
Medium m
Roughness c ±0.4 ±1 ±2 ±4
Coarsest v
Note: For the meanings of chamfering radius and chamfering height, see GB/T6403.4
(GB/1804-2000). Limit deviation values of angular dimensions
Tolerance class Length segment
～10 >10～50 >50～120 >120～400 >400
Precision f ±1° ±30′ ±20′ ±10′ ±5′
Medium m
Roughness c ±1°30′ ±1° ±30′ ±15′ ±10′
Most rough v ±3° ±2° ±1° ±30′ ±20′
(GB/T1184-1996) Unannotated tolerance values for straightness and flatness
Basic length range
≤10 >10～30 >30～100 & gt;100～300 >300～1000 >1000～3000
H 0.02 0.05 0.1 0.2 0.3 0.4
K 0.05 0.1 0.2 0.4 0.6 0.8
L 0.1 0.2 0.4 0.8 1.2 1.6
(GB/ T1184-1996)Perpendicularity unannotated tolerance value
Tolerance grade Basic length range
≤100 >100~300 >300~1000 >1000~3000
H 0.2 0.3 0.4 0.5
K 0.4 0.6 0.8 1
L 0.6 1 1.5 2
(GB/T1184-1996)Symmetry unnoted tolerance value
Basic length range
≤100 >100~300 >300~1000 >1000~3000
H 0.5
K 0.6 0.8 1
L 0.6 1 1.5 2
(GB/T1184-1996) Unannotated Tolerance Values of Circular Runout
Circular Runout Tolerance Value
H 0.1
K 0.2
L 0.5
Selection and Application of Tolerance Grades
Selection and Application of Tolerance Grades
Scope of Tolerance Grades and Examples
IT01 is used for particularly precise dimensioning references, such as particularly precise standardized blocks
IT0 is used for particularly precise dimensioning references and precision fit dimensions of special importance to astronautics. For example, particularly precise standard blocks, individual particularly important dimensions of precision machine parts, proofreading inspection of IT6 grade shaft gages for proofreading gages
IT1 Used for precision dimensional transfer reference, high-precision measuring tools, particularly important for individual precision fit dimensions. For example, high-precision standard gages, checking gages for IT7 to IT9 grade shaft gages, and individual, particularly important dimensions of precision machine parts
IT2 is used for high-precision measuring tools, and particularly important dimensions of precision fits. For example, inspection of IT6 to IT7 level workpiece gages with dimensional manufacturing tolerances, checking and inspection of IT8 to IT11 level shaft gages with checking plug gages, and the dimensions of individual particularly important precision machine parts
IT3 is used for precision measuring tools, high-precision precision fits for small-sized parts, as well as shaft diameters and housing bores that fit with C-class rolling bearings. For example, inspection gages for workpieces of classes IT8 to IT11 and proofreading gages for shafts of classes IT9 to IT13, machine tool spindles mated with the inner ring bores of particularly precise P4 rolling bearings (diameters up to 100mm), journals of precision and high-speed machinery, housing bores mated with the outer rings of P4 radial ball bearings, and particularly precise individual bores of navigational instruments in the aeronautical and marine industries. Small size parts of the accuracy of the fit.
IT4 is used for precision measuring tools, high-precision precision fits and P4 and P5 grade rolling bearing fits for shaft diameters and housing bores. For example, inspection of IT9 to IT12 level workpiece with the gauge and proofreading IT12 to IT14 level shaft with the proofreading gauge, and P4 level bearing hole (hole diameter >100mm) and with the P5 level bearing hole with the spindle of the machine tool, precision machinery and high-speed mechanical journals, and P4 level bearings with the machine tool housing holes, diesel engine piston pins and piston pin seat aperture, high-precision (level 1 to 4) Gear reference hole or shaft diameter, aviation and marine industry with special precision instruments of the aperture
IT5 for the fit tolerance requirements are very small, shape tolerance requirements are very high under the regulations, this type of tolerance level can make the nature of the fit is relatively stable, equivalent to the old national standard in the highest precision for the machine tool, engine and instrumentation in the particularly important with the size of the general mechanical application is less. For example, the inspection of IT11 to IT14 level workpiece with the gauge and proofreading IT14 to IT15 level shaft with the proofreading gauge, and P5 level rolling bearing with the machine tool box hole, and E level rolling bearing hole with the machine tool spindle, precision machinery and high-speed mechanical journal, machine tool tailstock sleeve, high-precision indexing plate journal, indexing head spindle, precision screw reference journal, high-precision boring bushing outer diameter, and so on; Engine in the spindle instrumentation in the precision hole fit, 5 precision gears of its hole and 5, 6 precision gears of the reference shaft
IT6 with the surface of a high degree of uniformity requirements to ensure a high degree of fit properties, the use of stable and reliable, equivalent to the old national standard of the 2-level shafts and 1 level of precision holes, widely used in the mechanical important with, for example, inspection of the IT12 to IT15 level workpieces. For example, inspection of IT12 to IT15 level workpieces and proofreading IT15 to IT16 level shaft with the proofreading gauge; with E-class bearings to match the shell holes and roller bearings to match the machine tool spindle journals, machine tool manufacturing in the assembled bronze worm gears, wheel housing OD mounting gears, worm gears, couplings, pulleys, cam journals; machine tool screw bearing journals, rectangular spline diameter of the centering, rocker drilling machine columns, etc.; the machine tool fixture guides the outer diameter dimensions, precision instruments in the Outside diameter size, precision instruments in the precision shaft, aviation and marine instrumentation in the precision shaft, automated instrumentation, postal and telecommunications machinery, watches in the particularly important shaft, the engine in the outer diameter of the cylinder liner, crankshaft journal, piston pin, connecting rod bushings, connecting rod and the outer diameter of the axle shaft tile; 6 accuracy of the reference hole of the gears and the accuracy of the reference journal of the gears of the 7, 8, special precision such as the top diameter of the gears of the precision of the 1 or 2
IT7 is widely used in general machinery, the application of conditions similar to IT6, but the precision is slightly lower, equivalent to the old national standard of intermediate precision shafts or level 2 precision hole tolerance. For example, the inspection of IT14 to IT16 level workpiece with the gauge and proofreading IT16 level shaft with the proofreading gauge; machine tools in the assembled bronze worm wheel rim aperture, couplings, pulleys, cams and other apertures, machine tool chuck seat holes, rocker arm drilling machine rocker arm holes, lathe screw bearing holes, machine tool chuck guides the inner hole, the engine in the connecting rod holes, piston holes, hinged studs positioning holes; the important components of textile machinery, printing and dyeing machinery require Important parts in textile machinery, printing and dyeing machinery in the higher requirements of the parts, precision instruments with precision holes, electronic computers, electronic instruments, meters, important holes, automation instrumentation in the important holes, 7, 8 precision gear reference holes and 9, 10 precision gear reference shaft
IT8 in the mechanical manufacturing belongs to the medium precision, in the instrument, instrumentation and watch manufacturing, because the basic In the instrument, instrument and clock manufacturing, because of the basic size is small, so it belongs to the higher precision range, in agricultural machinery, textile machinery, printing and dyeing machinery, bicycles, sewing machines, medical equipment in a wide range of applications. For example, the inspection of IT16 level workpiece with the gauge, bearing housing bushings along the width of the dimensions of the fit, the watch across the tooth axis, pawl dial wheel with the clamping plate of the radio instrumentation in the general fit,
IT9 application conditions are similar to IT8, but the accuracy of lower than the IT8 when used than the old national standard level 4 precision tolerance value is slightly larger. For example, machine tools and holes in the outer diameter of the bushing, the manipulator and the shaft, idling pulley and the shaft, the shaft of the control system and bearings, etc., textile machinery, printing and dyeing machinery in the general fit with the parts, the engine in the oil pump bore, the inner hole of the valve guide, the flywheel and flywheel bushing with the general size of automation instrumentation, the requirements of the watch in the parts of the size of the unnotched tolerance, the key width of the key in the joint with the dimensions, the key width with the dimensions, and the key width of the key. Typewriters in the moving parts of the fit size
IT10 application conditions are similar to IT9, but the requirements of the accuracy is lower than the IT9 when used, equivalent to the old national standard of the 5 level of precision tolerances. For example, electronic instruments and meters in the bracket fit, navigation instruments in the insulating bushing holes and converging ring bushing shaft, typewriters in the riveted parts of the size of the fit, the basic size of the watch is less than 18 mm when the general requirements of the size of the unannotated tolerance, and greater than 18 mm requires higher unannotated tolerance dimensions, the engine in the oil seal retaining ring holes with the crankshaft pulley hub with the dimensions of the fit
IT11 Widely used in the gap is large, and there are significant changes will not cause danger, can also be used to match the lower precision, assembly allows a larger gap, equivalent to the old national standard of precision tolerance of 6. For example, the flange stop and holes on the machine tool, slider and slip gear, grooves, etc.; agricultural machinery, locomotive carcase parts and stamping parts, watch manufacturing in the unimportant parts, watch manufacturing tools and equipment in the unnotated tolerance size, textile machinery in the rougher activities with the printing and dyeing machinery in the requirements of the lower with the size of the grinder in the manufacture of threaded couplings and rough dynamic couplings, do not make Measuring reference for the gear top circle diameter tolerance
IT12 fit accuracy requirements are very low, there is a large gap after assembly, suitable for basically no fit requirements of the parts, the requirements of the higher limit deviation of the dimensions of the unannotated tolerance, than the old national standard of precision tolerance of the 7th level is slightly smaller. For example, non-matching dimensions and inter-process dimensions, engine separator rod, watch manufacturing process equipment in the unnotated tolerance dimensions, the computer industry in the metal processing of the unnotated tolerance dimensions of the limit deviation, the machine tool manufacturing industry, wrench holes and the wrench seat coupling, etc.
IT13 Application conditions are similar to those of IT12, but it is slightly larger than the old national standard tolerance of precision grade 7. For example, non-matching dimensions and inter-process dimensions, computer, typewriter in the cutting parts and disc holes, two holes in the center distance of the center of the unannotated tolerance dimensions
IT14 For non-matching dimensions and dimensions that are not included in the dimensional chain, equivalent to the old national standard of precision tolerance of grade 8. For example, in machine tools, automobiles, tractors, metallurgical machinery, mining machinery, petrochemical, electrical machinery, electrical appliances, instruments, aviation and navigation, medical equipment, clocks and watches, bicycles, sewing machines, paper and textile machinery and other machined parts in the limit deviation of the unannotated tolerance dimensions
IT15 is used for the non-coincidental dimensions and the dimensions that are not included in the dimensional chain, which is equivalent to the old national standard of precision tolerances of grade 9. Tolerance. For example, for stamping parts, wood mold casting parts, and heavy machine tool manufacturing, the limit deviation of dimensions with unannotated tolerance when the basic size is larger than 3,150 mm
IT16 is used for non-matching dimensions and is equivalent to the old national standard precision tolerance of class 10. For example, the dimensions of cast parts in typewriters, the dimensions of the outer dimensions of cases in the radio manufacturing industry, the general dimensions of the outer dimensions of surgical instruments, the dimensions used for bending and extension machining, the dimensions of wooden parts in textile machinery, the dimensions of plastic parts, the dimensions of wood mold manufacturing and free forging
IT17 IT18 For non-matching dimensions, equivalent to the old national standard tolerance of grade 11 or 12 precision for plastics molding. dimensions, general external dimensions in surgical instruments, tolerances for dimensions for cold work and welding