Overview
ISO 8667:1992 - Commercial vehicles and buses - Cross-tooth gearbox flanges, type T - defines the nominal dimensions, tolerances and designation rules for type T cross-tooth (form‑locking) gearbox flanges used on heavy commercial vehicles and buses. The standard ensures interchangeability between mating flanges and connected drivetrain components by specifying the critical dimensional and tolerance parameters that affect fit, alignment and assembly.
Key topics and technical requirements
- Scope and purpose: Specifies the dimensions and tolerances that affect interchangeability of type T cross‑tooth gearbox flanges and their mating elements on commercial vehicles and buses.
- Form‑locking tooth interface: Flanges use interlocking teeth that engage at about 70° to provide self‑centering and torque transmission by the tooth profile rather than by friction on bolts.
- Bolt count and sizes: Type T design reduces bolt number and size compared with conventional flanges (document cites problems with large fasteners such as M16 tightened to ~300 Nm). This lowers assembly torque requirements and simplifies maintenance.
- Designation rules: Flanges compliant with the standard are identified by the standard reference, type code T and the flange dimension (example: “Flange ISO 8667 – T 150”).
- Dimensional and tolerance tables: Nominal dimensions and tolerances for key diameters, tooth segments and assembly features are given in the standard. The document also permits specific optional features (e.g., additional grooves for forged parts; optional seven‑groove layout for some sizes).
- Manufacturing and measurement: Guidance covers production methods (milling with special cutters for small series; broaching for large series) and measurement controls including module error limits (example module errors: unit 0.02, global 0.03, between‑teeth 0.02) and specified surface finish requirements.
- Interchangeability controls: Measurement locations and runout/flatness checks are specified to guarantee interchangeability across manufacturers.
Applications and users
- Who uses it: OEMs (truck and bus manufacturers), transmission and driveline suppliers, aftermarket parts manufacturers, fleet maintenance engineers, quality/inspection teams and standards/engineering departments.
- Practical benefits:
- Faster assembly/disassembly and simplified maintenance for heavy vehicles and special vehicles requiring rapid drivetrain changes.
- Improved shaft alignment and reduced play compared with traditional bolted flanges.
- Lower axial loads on bolts because torque is carried by tooth engagement, enabling smaller fasteners.
- Typical use cases: Gearbox-to-driveshaft couplings in heavy trucks, buses and special‑purpose vehicles where space constraints and maintenance speed are critical.
Related standards
- ISO 7646 and ISO 7647 - flanges type A and S (referenced in the ISO 8667 introduction) - for other gearbox flange types used on commercial vehicles.
Keywords: ISO 8667, cross‑tooth gearbox flange, type T, commercial vehicles, buses, flange dimensions, interchangeability, gearbox coupling, transmission flanges.
