ISO 4468:2020

Overview - ISO 4468:2020 (Gear hobs - Accuracy requirements)

ISO 4468:2020 specifies accuracy requirements and inspection methods for general-purpose gear hobs (modules 0.5 to 40). It covers hobs used to produce gears conforming to ISO 53 and ISO 54 and applies to both spur and helical gears, including solid (monobloc) and inserted-blade hobs. The standard defines graded precision classes (4A, 3A, 2A, A, B, C, D - with 4A the highest precision) and gives permitted tolerances for both elemental and composite (line-of-action) tests.

Keywords: ISO 4468, gear hobs accuracy, hob tolerances, gear hobbing, spur gears, helical gears

Key technical topics and requirements

• Module range and scope: Applies to hobs of module 0.5–40 intended for ISO 53/54 gears. Nominal hob dimensions are referenced to ISO 2490 (Annex A).
• Accuracy grades: Seven precision grades (4A → D) for elemental hob features; grade selection determines tolerance factors.
• Elemental vs composite tests: Two inspection groups are provided:
  • Elemental tests (measuring individual hob features)
  • Composite (line-of-action) tests (measurements taken along the cutting edge) If no prior agreement exists, a hob is accepted into the specified grade if it meets either test method.
• Test types (examples):
  • Radial runout of hub diameter and tips of teeth
  • Axial runout of hub face
  • Straightness and radial alignment over cutting depth
  • Adjacent and total spacing of cutting faces (gashes)
  • Gash lead deviation, tooth profile deviation, tooth thickness and addendum differences
  • Lead deviations (adjacent, one axial pitch, three axial pitches)
  • Line-of-action adjacent and total deviations
• Tolerance derivation and adjustments: Tolerances are computed from defined base values and graded multipliers. Oversize hobs (outside diameter larger than Annex A) require increasing standard tolerances by a factor equal to half the percent oversize.
• Measurement practice: The manufacturer selects the measurement method and calibrated equipment unless otherwise agreed; standard bore tolerances and alignment checks (reference mandrel) are specified.

Practical applications - who uses ISO 4468

• Hob manufacturers - to design, manufacture and certify hob accuracy and supply to agreed precision classes.
• Gear manufacturers and machine shops - to specify hob quality for achieving required gear performance.
• Quality / metrology engineers - to set inspection routines, select test methods (elemental vs line-of-action), and interpret tolerance results.
• Procurement and compliance teams - to write purchase specifications and acceptance criteria for cutting tools.

Related standards

• ISO 53, ISO 54 (gear tooth systems)
• ISO 2490 (hob nominal dimensions - Annex A reference)
• ISO 286-2, ISO 1122-1, ISO 2768-1 (referenced for tolerances and terminology)

ISO 4468 is essential for consistent, repeatable hob quality that supports accurate gear generation and predictable gear performance.