Hole & Shaft Tolerances Deviations And Fits – ISO 286

Designation of the tolerance class

General

The tolerance class shall be designated by the combination of an upper-case letter(s) for holes and lowercase letters for shafts identifying the fundamental deviation and by the number representing the standard tolerance grade.

EXAMPLE (ISO 286): H7 (holes), h7 (shafts). “H” and “h” indicate the tolerance position, while “7” represents the tolerance grade.

Size and its tolerance

A size and its tolerance shall be designated by the nominal size followed by the designation of the required tolerance class (ISO 286), or shall be designated by the nominal size followed by + and/or − limit deviations (see ISO 14405).

In the following examples the indicated limit deviations are equivalent to the indicated tolerance classes.

EXAMPLE:

ISO 286

ISO 14405

32 H7

+0.025

80 js15

80 ± 0.6

100 g6

100

-0.012

-0.034

Figure 1: Hole tolerance position

Hole tolerance deviations: A, B, C, CD, D, E, EF, F, FG, G, H, JS, J, K, M, N, P, R, S, T, U, V, X, Y, Z, ZA, ZB, ZC.

Figure 2: Shaft tolerance position

Shaft tolerance deviations: a, b, c, cd, d, e, ef, f, fg, g, h, js, j, k, m, n, p, r, s, t, u, v, x, y, z, za, zb, zc.

Selection of tolerance classes

Whenever possible, the tolerance classes should be chosen from those corresponding to the classes for holes and shafts given in Figures 3 and 4, respectively. The first choice should preferably be made from the tolerance classes, shown in the frames.

The tolerance classes of Figures 3 and 4 apply only to general purposes which do not require a more specific selection of tolerance classes. Keyways, for example, require a more specific selection.

Figure 3: Hole tolerance class selection

General purposes hole tolerance class: A11, B11, C10, C11, D9, D10, D11, E8, E9, E10, F7, F8, F9, G6, G7, H6, H7, H8, H9, H10, H11, JS6, JS7, JS8, K6, K7, K8, M6, M7, M8, N6, N7, N8, P6, P7, P8, R6, R7, R8, S6, S7, T6, T7, U7, X7.

Figure 4: Shaft tolerance class selection

General purposes shaft tolerance class: a11, b9, b11, c9, c11, d8, d9, d10, e7, e8, e9, f6, f7, f8, g5, g6, h5, h6, h7, h8, h9, h10, h11, js5, js6, js7, k5, k6, k7, m5, m6, m7, n5, n6, n7, p5, p6, p7, r5, r6, r7, s5, s6, s7, t5, t6, t7, u6, u7, x6.

Determination of a fit

General

There are two possibilities to determine a fit. Determination of a fit either by experience or by calculating the permissible clearances and/or interferences derived from the functional requirements and the production possibilities of the mating parts.

A fit between mating features shall be designated by

the common nominal size;
the tolerance class for the hole;
the tolerance class for the shaft.

EXAMPLE 52 H7/g6

Selection of the fit system

The first decision to be made is whether to adopt the “hole-basis fit system” (hole H) or the “shaft-basis fit system” (shaft h). However, it has to be noted, that there are no technical differences regarding the function of the parts. Therefore the choice of the system should be based on economic reasons.

The “hole-basis fit system” should be chosen for general use. This choice would avoid an unnecessary multiplicity of tools (e.g. reamers) and gauges.

The “shaft-basis fit system” should only be used where it will convey unquestionable economical advantages (e.g. where it is necessary to be able to mount several parts with holes having different deviations on a single shaft of drawn steel bar without machining the latter).

Figure 5: Preferable fits of the hole-basis system

Hole-basic fit system:

Clearance fits: H6/g5, H6/h5, H7/f6, H7/g6, H7/h6, H8/e7, H8/f7, H8/h7, H8/d8, H8/e8, H8/f8, H8/h8, H9/d8, H9/e8, H9/f8, H9/h8, H10/b9, H10/c9, H10/d9, H10/e9, H10/h9, H11/b11, H11/c11, H11/d10, H11/h10.
Transition fits: H6/js5, H6/k5, H6/m5, H7/js6, H7/k6, H7/m6, H7/n6, H8/js7, H8/k7, H8/m7.
Interference fits: H6/n5, H6/p5, H7/p6, H7/r6, H7/s6, H7/t6, H7/u6, H7/x6, H8/s7, H8/u7.

Figure 5: Preferable fits of the shaft-basis system

Shaft-basic fit system:

Clearance fits: G6/h5, H6/h5, F7/h6, G7/h6, H7/h6, E8/h7, F8/h7, H8/h7, D9/h8, E9/h8, F9/h8, H9/h8, E8/h9, F8/h9, H8/h9, D9/h9, E9/h9, F9/h9, H9/h9, B11/h9, C10/h9, D10/h9, H10/h9.
Transition fits: JS6/h5, K6/h5, M6/h5, JS7/h6, K7/h6, M7/h6, N7/h6.
Interference fits: N6/h5, P6/h5, P7/h6, R7/h6, S7/h6, T7/h6, U7/h6, X7/h6.

Determination of a specific fit by calculation

In certain special functional cases, it is necessary to calculate the permissible clearances and/or interferences derived from the functional requirements of the mating parts. The clearances and/or interferences and the span of the fit obtained from that calculation have to be transformed into limit deviations and if possible into tolerance classes.

Hole & Shaft Tolerances Lookup Tool

Hole Tolerance (mm)

0.000

Standard tolerance class

Standard hole tolerance class

Synoptic representation of tolerance classes for holes for basic sizes less than or equal to 500 mm

Position A: A9, A10, A11, A12, A13
Position B: B8, B9, B10, B11, B12, B13
Position C: C8, C9, C10, C11, C12, C13
Position CD: CD6, CD7, CD8, CD9, CD10
Position D: D6, D7, D8, D9, D10, D11, D12, D13
Position E: E5, E6, E7, E8, E9, E10
Position EF: EF3, EF4, EF5, EF6, EF7, EF8, EF9, EF10
Position F: F3, F4, F5, F6, F7, F8, F9, F10
Position FG: FG3, FG4, FG5, FG6, FG7, FG8, FG9, FG10
Position G: G3, G4, G5, G6, G7, G8, G9, G10
Position H: H1, H2, H3, H4, H5, H6, H7, H8, H9, H10, H11, H12, H13, H14, H15, H16, H17, H18
Position JS: JS1, JS2, JS3, JS4, JS5, JS6, JS7, JS8, JS9, JS10, JS11, JS12, JS13, JS14, JS15, JSl6, JS17, JS18
Position J: J6, J7, J8
Position K: K3, K4, K5, K6, K7, K8, K9, K10
Position M: M3, M4, M5, M6, M7, M8, M9, M10
Position N: N3, N4, N5, N6, N7, N8, N9, N10, N11
Position P: P3, P4, P5, P6, P7, P8, P9, P10
Position R: R3, R4, R5, R6, R7, R8, R9, R10
Position S: S3, S4, S5, S6, S7, S8, S9, S10
Position T: T5, T6, T7, T8
Position U: U5, U6, U7, U8, U9, U10
Position V: V5, V6, V7, V8
Position X: X5, X6, X7, X8, X9, X10
Position Y: Y6, Y7, Y8, Y9, Y10
Position Z: Z6, Z7, Z8, Z9, Z10, Z11
Position ZA: ZA6, ZA7, ZA8, ZA9, ZA10, ZA11
Position ZB: ZB7, ZB8, ZB9, ZB10, ZB11
Position ZC: ZC7, ZC8, ZC9, ZC10, ZC11

Synoptic representation of tolerance classes for holes for basic sizes greater than 500 mm and less than or equal to 3150 mm

Position D: D6, D7, D8, D9, D10, D11, D12, D13
Position E: E6, E7, E8, E9, E10
Position F: F6, F7, F8, F9
Position G: G6, G7, G8
Position H: H1, H2, H3, H4, H5, H6, H7, H8, H9, H10, H11, H12, H13, H14, H15, H16, H17, H18
Position JS: JS1, JS2, JS3, JS4, JS5, JS6, JS7, JS8, JS9, JS10, JS11, JS12, JS13, JS14, JS15, JS16, JS17, JS18
Position K: K6, K7, K8
Position M: M6, M7, M8
Position N: N6, N7, N8, N9
Position P: P6, P7, P8, P9
Position R: R6, R7, R8
Position S: S6, S7, S8
Position T: T6, T7, T8
Position U: U6, U7, U8

Standard shaft tolerance class

Synoptic representation of tolerance classes for shafts for basic sizes less than or equal to 500 mm

Position a: a9, a10, a11, a12, a13
Position b: b9, b10, b11, b12, b13
Position c: c8, c9, c10, c11, c12
Position cd: cd5, cd6, cd7, cd8, cd9, cd10
Position d: d5, d6, d7, d8, d9, d10, d11, d12, d13
Position e: e5, e6, e7, e8, e9, e10
Position ef: ef3, ef4, ef5, ef6, ef7, ef8, ef9, ef10
Position f: f3, f4, f5, f6, f7, f8, f9, f10
Position fg: fg3, fg4, fg5, fg6, fg7, fg8, fg9, fg10
Position g: g3, g4, g5, g6, g7, g8, g9, g10
Position h: h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11, h12, h13, h14, h15, h16, h17, h18
Position js: js1, js2, js3, js4, js5, js6, js7, js8, js9, js10, js11, js12, js13, js14, js15, js16, js17, js18
Position j: j5, j6, j7, j8
Position k: k3, k4, k5, k6, k7, k8, k9, k10, k11, k12, k13
Position m: m3, m4, m5, m6, m7, m8, m9
Position n: n3, n4, n5, n6, n7, n8, n9
Position p: p3, p4, P5, P6, P7, p8, P9, P10
Position r: r3, r4, r5, r6, r7, r8, r9, r10
Position s: s3, s4, s5, s6, s7, s8, s9, s10
Position t: t5, t6, t7, t8
Position u: u5, u6, u7, u8, u9
Position v: v5, v6, v7, v8
Position x: x5, x6, x7, x8, x9, x10
Position y: y6, y7, y8, y9, y10
Position z: z6, z7, z8, z9, z10, z11
Position za: za6, za7, za8, za9, za10, za11
Position zb: zb7, zb8, zb9, zb10, zb11
Position zc: zc7, zc8, zc9, zc10, zc11

Synoptic representation of tolerance classes for shafts for basic sizes greater than 500 mm and less than or equal to 3150 mm

Position d: d7, d8, d9, d10, d11
Position e: e6, e7, e8, e9, e10
Position f: f6, f7, f8, f9
Position g: g6, g7, g8
Position h: h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11, h12, h13, h14, h15, h16, h17, h18
Position js: js1, js2, js3, js4, js5, js6, js5, js7, js8, js9, js10, js11, js12, js13, js14, js15, js16, js17, js18
Position k: k6, k7, k8, k9, k10, k11, k12, k13
Position m: m6, m7
Position n: n6, n7
Position p p6, p7, p8
Position r: r6, r7, r8
Position s: s6, s7, s8
Position t: t6, t7
Position u: u6, u7, u8