1. Technical knowledge center
  2. Principles of selecting bearing fits
  3. Hole tolerance fields H7-H11
  4. Typical fits of bearing nodes
  5. Reconditioning tolerances of holes for pins and bushings
  6. DIN 471 / DIN 472 circlips
  7. Slide bushings – types and selection
  8. Installation and removal of bearings – technical principles

Introduction

Tolerance zones H7–H11 define the permissible dimensional deviations of holes in the basic hole system in accordance with ISO 286-2.

This system is widely used in machine construction, hole regeneration and in the selection of bearing, bushing and pin fits.

W polu tolerancji H dolna odchyłka wynosi 0, co oznacza, że rzeczywisty wymiar otworu nie może być mniejszy od nominalnego.

Base Hole System – Field H

In the basic hole system:

Lower deviation (EI) = 0
The upper deviation (ES) depends on the tolerance class (H7–H11)

Example:

Ø50 H7 hole
→ actual range: 50.000 mm – 50.025 mm

Hole tolerance table H7–H11 (mm)

Nominal diameter range [mm]H7H8H9H10H11
3 – 60 / +0.0120 / +0.0180 / +0.0300 / +0.0480 / +0.075
6 – 100 / +0.0150 / +0.0220 / +0.0360 / +0.0580 / +0.090
10 – 180 / +0.0180 / +0.0270 / +0.0430 / +0.0700 / +0.110
18 – 300 / +0.0210 / +0.0330 / +0.0520 / +0.0840 / +0.130
30 – 500 / +0.0250 / +0.0390 / +0.0620 / +0.1000 / +0.160
50 – 800 / +0.0300 / +0.0460 / +0.0740 / +0.1200 / +0.190
80 – 1200 / +0.0350 / +0.0540 / +0.0870 / +0.1400 / +0.220
120 – 1800 / +0.0400 / +0.0630 / +0.1000 / +0.1600 / +0.250
180 – 2500 / +0.0460 / +0.0720 / +0.1150 / +0.1850 / +0.290
250 – 3150 / +0.0520 / +0.0810 / +0.1300 / +0.2100 / +0.320
315 – 4000 / +0.0570 / +0.0890 / +0.1400 / +0.2300 / +0.360
400 – 5000 / +0.0630 / +0.0970 / +0.1550 / +0.2500 / +0.400
500 – 6300 / +0.0700 / +0.1100 / +0.1750 / +0.2800 / +0.440
630 – 8000 / +0.0800 / +0.1250 / +0.2000 / +0.3200 / +0.500
800 – 10000 / +0.0900 / +0.1400 / +0.2300 / +0.3600 / +0.560

Interpretation of the table

For the selected nominal diameter range:

  1. Read the upper deviation for a given tolerance zone.
  2. Add it to the nominal dimension.
  3. The resulting range determines the actual range of hole drilling.

Application in practice

H7 – used for bearing seats and precision fits.
H8 – general structural fits.
H9 – less stressed components.
H10–H11 – designs with lower precision requirements.

When regenerating holes for bushings and pins, the H7 or H8 field is most often used, depending on the required accuracy.

Reference to standards

Dimensional tolerances are specified in:

ISO 286-1 – Tolerances and Fits
ISO 286-2 – Numerical Deviations