International Tolerance Grade level and application on it

refer to wikipedia,IT Grade refers to the International Tolerance Grade of an industrial process defined in ISO 286. This grade identifies what tolerances a given process can produce for a given dimension.
International Tolerance grades are calculated as following:


where :

• T is the tolerance in micrometres [µm]
• D is the geometric mean dimension in millimeters [mm]
• ITG is the IT Grade, a positive integer.

Decide the level of precision of the level known as the resilience level, the national standard is separated into 20 grades, from IT01, IT00, IT1, IT2 ~ IT18. The littler the number, the higher the resilience level (machining exactness), the littler the admissible scope of variety (resistance esteem), and the more noteworthy the trouble of machining. In particular, you can question the mechanical outline manual, the diverse fundamental measurements utilizing a similar resilience level, the resistance range is likewise unique.

International Tolerance Grade Chart

Basic Size (mm)		INTERNATIONAL  TOLERANCE GRADES
		IT1	IT2	IT3	IT4	IT5	IT6	IT7	IT8	IT9	IT10	IT11	IT12	IT13	IT14	IT15	IT16	IT17	IT18
above	Up to (include)	TOLERANCE
		micrometer									milimeter
-	3	0.8	1.2	2	3	4	6	10	14	25	40	60	0.1	0.14	0.25	0.4	0.6	1	1.4
3	6	1	1.5	2.5	4	5	8	12	18	30	48	75	0.12	0.18	0.3	0.48	0.75	1.2	1.8
6	10	1	1.5	2.5	4	6	9	15	22	36	58	90	0.15	0.22	0.36	0.58	0.9	1.5	2.2
10	18	1.2	2	3	5	8	11	18	27	43	70	110	0.18	0.27	0.43	0.7	1.1	1.8	2.7
18	30	1.5	2.5	4	6	9	13	21	33	52	84	130	0.21	0.33	0.52	0.84	1.3	2.1	3.3
30	50	1.5	2.5	4	7	11	15	25	39	62	100	160	0.25	0.39	0.62	1	1.6	2.5	3.9
50	80	2	3	5	8	13	18	30	46	74	120	190	0.3	0.46	0.74	1.2	1.9	3	4.6
80	120	2.5	4	6	10	15	20	35	54	87	140	220	0.35	0.54	0.87	1.4	2.2	3.5	5.4
120	180	3.5	5	8	12	18	23	40	63	100	160	250	0.4	0.63	1	1.6	2.5	4	6.3
180	250	4.5	7	10	14	20	25	46	72	115	185	290	0.46	0.72	1.15	1.85	2.9	4.6	7.2
250	315	6	8	12	16	23	27	52	81	130	210	320	0.52	0.81	1.3	2.1	3.2	5.2	8.1
315	400	7	9	13	18	25	32	57	89	140	230	360	0.57	0.89	1.4	2.3	3.6	5.7	8.9
400	500	8	10	15	20	27	36	63	97	155	250	400	0.63	0.97	1.55	2.5	4	6.3	9.7
500	630	9	11	16	22	32	40	70	110	175	280	440	0.7	1.1	1.75	2.8	4.4	7	11
630	800	10	13	18	25	36	44	80	125	200	320	500	0.8	1.25	2	3.2	5	8	12.5
800	1000	11	15	21	28	40	50	90	140	230	360	560	0.9	1.4	2.3	3.6	5.6	9	14
1000	1250	13	18	24	33	47	56	105	165	260	420	660	1.05	1.65	2.6	4.2	6.6	10.5	16.5
1250	1600	15	21	29	39	55	78	125	195	310	500	780	1.25	1.95	3.1	5	7.8	12.5	19.5
1600	2000	18	25	35	46	65	92	150	230	370	600	920	1.5	2.3	3.7	6	9.2	15	23
2000	2500	22	30	41	55	78	110	175	280	440	700	1100	1.75	2.8	4.4	7	11	17.5	28
2500	3150	26	36	50	68	96	135	210	330	540	860	1350	2.1	3.3	5.4	8.6	13.5	21	33

Aplication Area

Tolerarance level	Application and example
IT01	For special precision size transmission benchmarks, such as special precision standard mass
IT0	Used in the special precision of the size of the transmission reference and aerospace is particularly important in the precision with the size. For example, the special precision of the standard block, the individual is particularly important precision mechanical parts size, proofreading IT6 level shaft gauge gauge calibration
IT1	For precision size transmission benchmarks, high precision measuring tools are particularly important for extremely precise fit sizes. For example, high-precision standard gauges, proofreading of IT7 to IT9-class shaft gauge gauges, individually important precision mechanical parts dimensions
IT2	For high-precision measurement tools, particularly important precision fit size. Such as the size of the IT6 to IT7 grade gauges Manufacturing tolerances, proofreading of IT8 to IT11 grade shaft gauges, individually important precision mechanical parts Dimensions
IT3	For precision measurement tools, small parts of the precision of precision and with C-class rolling bearing with the shaft diameter and shell aperture. For example, check the IT8 to IT11 grade workpiece gauge and proofreading IT9 to IT13 class shaft gauge with the calibration gauge, and particularly sophisticated P4-type rolling bearing ring hole (diameter to 100mm) match the machine spindle, precision machinery and high-speed mechanical Journal, and P4-type radial ball bearing outer ring to match the shell aperture, aviation and navigation industry in the navigation equipment on the special precision of the individual small size parts with the accuracy.
IT4	For precision measurement tools, high precision precision and P4 level, P5 grade rolling bearing with the shaft diameter and shell aperture. For example, check the IT9 to IT12 grade workpiece gauges and proofreading IT12 to IT14 class shaft gauge gauge with the A4 level bearing hole (aperture> 100mm) and with the P5-class bearing hole matching machine spindle, precision machinery and high-speed mechanical Shafts, countershafts compatible with P4 bearings, piston rods for piston rods and piston pins, high precision (Class 1 to 4) gears for reference or shaft diameter, special precision for aircraft and marine applications Aperture
IT5	Used to meet the tolerance requirements are very small, high tolerance requirements of the Ordinance, such a tolerance level can make the degree of compatibility more stable, the equivalent of the old GB in the highest precision for the machine, engine and instrumentation is particularly important with the size, General machinery in the application of less. For example, check the IT11 to IT14 class workpiece gauges and proofreading IT14 to IT15 class shaft gauge gauge with the P5 level rolling bearing matching machine box hole, and E-level rolling bearing hole matching machine spindle, precision machinery and high-speed mechanical Shaft, machine tailstock sleeve, high-precision indexing journal, dividing head spindle, precision screw reference journal, high-precision boring sets of outside diameter; engine spindle instrument in the precision hole with the 5 Precision precision gears and their 5 and 6 precision gears of the reference axis
IT6	With a high uniformity of the surface requirements, to ensure a very high with the nature of the use of stable and reliable, equivalent to the old GB grade 2 axis and a precision hole, widely used in mechanical important for example, test IT12 to IT15 Class workpiece gauges and proofreading IT15 to IT16 class shaft gauge gauge; with E-class bearing matching housing hole and roller bearing with the matching of the machine tool spindle, machine tool manufacturing bronze worm gear, wheel shell diameter installation Gears, worm gears, couplings, pulleys, cam journals; machine tool nose support journal, rectangular spline centering diameter, radial drilling machine columns, etc .; machine fixture guide pieces of the outer diameter, precision instruments Precision shafts, precision axes in aeronautical and navigational instruments, automated instruments, post and telecommunications machinery, particularly important shafts in the watch, outside cylinder bore, crankshaft main journal, piston pin, connecting rod bushing, connecting rod and shaft Diameter; 6-level precision gear reference hole and 7, 8 precision gear reference journal, especially precision, such as 1 or 2 precision gear top circle diameter
IT7	Widely used in general machinery, the application of IT6 similar, but the accuracy is slightly lower, equivalent to the old national standard precision axis or 2 precision hole tolerance. Such as inspection of IT14 to IT16 grade workpiece gauges and proofreading IT16 grade shaft gauges calibration tool gauge; machine assembly in the bronze worm wheel rim diameter, coupling, pulley, cam and other aperture, machine chuck hole, radial drilling machine The crank hole of the lathe, the inner hole of the machine chuck guide, the connecting rod hole in the engine, the piston hole, the hinge stud positioning hole; the important parts in the textile machinery, the printing machinery Electronic equipment, electronic instruments, instruments in the important hole, automatic instrument in the important hole, 7, 8 precision gear reference hole and 9, 10 precision gears, precision instruments, precision instruments, Datum axis
IT8	In the manufacture of machinery, medium precision, in the manufacture of instruments, meters and watches, the basic size is small, so it is a high precision range, in the agricultural machinery, textile machinery, printing and dyeing machinery, bicycles, sewing machines, medical equipment, The For example, the inspection IT16 grade workpiece with the gauge, bearing bushings along the width of the size of the match, the spine in the watch spike, pawl dial wheel and plywood with the radio in the general match,
IT9	The application conditions are similar to those of IT8, but the accuracy is lower than that of IT8, which is slightly larger than the old GB 4 precision tolerance. For example, the shaft diameter of the machine tool and the hole, the control pieces and the shaft, the idling pulley and the shaft, the control system shaft and the bearing cooperate, the textile machinery, the printing machinery in the general cooperation parts, the engine oil pump body hole, The combination of the inner hole, the flywheel and the flywheel sleeve, the general fit size in the automatic instrument, the size of the non-bearing tolerance of the higher part in the watch, the key width of the single key connection, the fit size of the moving parts in the typewriter
IT10	The application conditions are similar to those of IT9, but require less accuracy than IT9, which is equivalent to the 5-level accuracy of the old national standard. For example, the electronic equipment, instrumentation on the bracket, the navigation equipment in the insulating bushing hole and the exchange ring bushing shaft, typewriter rivets with the size of the basic size of the watch is less than 18 mm when the general requirements Of the size, and greater than 18 mm require a higher non-tolerance size, the engine oil seal hole and the crankshaft belt with the size of the hub
IT11	Widely used in the gap is large, and there is a significant change will not cause dangerous occasions, can also be used for low precision, after assembly to allow a larger gap, equivalent to the old GB 6 precision tolerance. For example, the machine on the machine with the hole and the hole, slider and slip gear, groove, etc .; agricultural machinery, locomotive car parts and stamping processing with parts, watches and clocks in the manufacture of unimportant parts, watch manufacturing tools and Equipment does not pay the size of the tolerance, the rough cooperation of textile machinery, printing and dyeing machinery requires a lower fit size, grinding machine manufacturing in the thread connection and rough dynamic coupling, not for the measurement of the benchmark with the top circle diameter tolerance
IT12	With the accuracy requirements are very low, after assembly has a large gap for basically no requirements of the site, requiring a higher tolerance is not the size of the tolerance limit, than the old GB 7 precision tolerance slightly smaller. For example, the size of non-mating dimensions and the size of the process, the size of the engine separation rod, the size of the process equipment in the manufacture of the watch, the limit deviation of the dimensioned dimension of the metalwork in the computer industry, the connection of the wrench hole and the wrench in the machine tool manufacturing Wait
IT13	The application conditions are similar to those of IT12, but are slightly larger than the accuracy of the old GB 7 precision. For example, the size of the non-matching and the size of the process, the computer, typing machine in the cutting parts and wafer holes, two-hole center distance from the tolerance
IT14	For non-mating size and not included in the size of the chain size, equivalent to the old GB 8-level accuracy tolerance. For example, in the machine, automobile, tractor, metallurgical machinery, mining machinery, petrochemical, electrical, electrical, instrumentation, aviation navigation, medical equipment, watches, bicycles, sewing machines, paper and textile machinery parts The limit deviation
IT15	For non-mating size and not included in the size of the chain size, equivalent to the old national standard 9-level accuracy tolerance. For example, stamping parts, wood mold parts, heavy machine manufacturing, when the basic size is greater than 3 150 mm when the size of the tolerance is not tolerance
IT16	For non-matching size, equivalent to the old national standard 10-level accuracy tolerance. For example, the size of the cast in the typewriter, the dimensions of the box in the radio manufacturing industry, the general dimensions in the surgical instrument, the dimensions of the bending and extension, the size of the woodwork in the textile machinery, the size of the plastic parts, the manufacture and freedom of the mold Forged size
IT17 ~ IT18	For non-matching size, equivalent to the old GB of 11 or 12-level accuracy of the tolerance for plastic molding size, surgical instruments in the general dimensions, cold and welding with the size of the tolerance