ISO Tolerance Bands

The tolerance of size is normally defined as the difference between the upper and lower dimensions.

The need for tolerances to be identified on drawings is vital to allow assembly of parts in the desired way and interchangeability of parts as required in modern manufacturing methods.

ISO 286 implements 20 grades of accuracy to satisfy the requirements of different industries.

  • IT01,  IT0,   IT1,  IT2,   IT3,  IT4,  IT5,  IT6.. Production of gauges and instruments.
  • IT5,  IT6,  IT7,  IT8,  IT9,  IT10,  IT11,  IT12.. Precision and general Industry.
  • IT11,  IT14,   IT15,  IT16.. Semi finished products
  • IT16,  IT17,  IT18.. Structural Engineering
  • Examples in using above tables..

    Note: The tolerance band T is an absolute length value it does not have a negative value.

    Hole Dia 110mm H11,...

    Nearest zero ( El )= 110mm + 0mm = 110,000mm ..

    Furthest from zero ( ES )= 110mm + (0+ T=0,220)=110,220mm

    Resulting limits 110,000/110,220

    Shaft 110mm e9...
    Nearest zero ( es ) = 110mm - 0,072=109,928mm...

    Furthest from zero ( ei ) = 110mm - (0,072 + T=0,087) = 109,841mm

    Resulting limits 109,928/109,841

    Note for the tolerance bands which can be either side of zero, (J,K,N,j )

    The diagrams provided with the table clearly show calculation needed.e.g. consider Hole 300K7.

    T= 52 micrometres (0,052mm). Limit nearest zero ( K ) ES = 16 micrometres = (0,016mm)

    Limit furthest from zero ( K ) El = (0,016- 0,052)= -0,036

    Limits therefore (300 -0,036) = 299,964..and ...300+0,016= 300,016 limits 299,964/300,016 tolerance band in micrometres = (m-6) based on ISO 286  IT Grades 1 to 14  


    ISO Tolerance Band "T " 0 to 315mm

    Nominal Sizes (mm)
    over1361018305080120 180250
    inc.361018305080120180250315
    IT GradeTolerance Grade T
    10.8111.21.51.522.53.54.56
    21.21.51.522.52.53 4578
    322.52.53445681012
    434456 7810121416
    545689111315182023
    668 91113161922252932
    71012151821253035404652
    81418222733394654637281
    925303643526274 87100115130
    104048587084100120140160185210
    116075 90110130160190220250290320
    12100120150180210250300350400 460520
    13140180220270330390460540630720810
    14250300360 430520620740870100011501300

    ISO Tolerance Band "T " 315 to 3150mm

    Nominal Size
    Over25031540050063080010001250160020002500
    Inclusive315400 500630800100012501600200025003150
    IT GradeTolerance Grade T
    16789 10111315182226
    289101113151821253036
    3 1213151618212429354150
    4161820222528333946 5568
    52325273236404755657896
    63236404450 56667892110135
    7525763708090105125150175210
    881 8997110125140165195230280330
    9130140155175200230260310 370440540
    10210230250280320360420500600700860
    11320360400 44050056066078092011001350
    12520570630700800900105012501500 17502100
    1381089097011001250140016501950230028003300
    14130014001550 17502000230026003100370044005400