Overview
ISO 500-1:2014 specifies general requirements for rear-mounted power take-offs (PTOs) of types 1, 2, 3 and 4 on agricultural tractors with a track setting wider than 1 150 mm. The standard covers PTO classification, nominal speeds, safety requirements, and the required dimensions for the master shield (PTO shield) and surrounding clearance zone. It replaces the 2004 edition and complements ISO 500-2 (narrow-track tractors) and ISO 500-3 (PTO geometry).
Key topics and requirements
- PTO classification: Rear-mounted PTOs are classified into four types (1–4) with defined nominal rotation characteristics and spline geometries.
- Rotation direction: PTO rotation is specified as clockwise when viewed from the rear of the tractor (exceptions for ground-driven reverse operation noted).
- Nominal speeds and multiple ratios: The standard addresses nominal PTO speeds and requires safeguards where multiple gearbox ratios are provided so inadvertent shifting (especially into a higher-speed ratio) cannot occur.
- Engaged/speed indicator: A means must be provided to indicate when the PTO is operating and which nominal speed is selected.
- Master shield (PTO shield):
- Must be supplied and fixed to the tractor by the manufacturer (equivalent protection devices are permitted if they provide the same safety level and include an attachment point for immobilising the driveline guard).
- May include a movable section to facilitate shaft connection; moving parts must resist unintentional displacement.
- If usable as a step, the shield must withstand a 1 200 N static vertical load without permanent deformation.
- Optional non-rotating cover may be provided for when the PTO is not in service.
- Shield opening and clearance-zone dimensions: The standard specifies dimensional control values for shield openings and the PTO clearance zone. Example values from Table 2:
- Opening “a”: Type 1 & 2 = 80 mm; Type 3 = 95 mm; Type 4 = 105 mm
- “m”: 125 mm (types 1–2) and 150 mm (types 3–4)
- “p”: 290 mm (types 1–2) and 360 mm (types 3–4)
- Other control dimensions (SRr, k, n, r, angles α/β/γ) are defined in the standard.
Applications and users
- Manufacturers of agricultural tractors and driveline components (PTO shafts, shields, hitches) use ISO 500-1 to design compliant rear PTO interfaces.
- Agricultural equipment designers, safety engineers, test labs, and regulatory authorities reference it for product safety, type approval, and conformity assessment.
- Useful for service technicians and fleet managers to understand safe connection clearances and protective device requirements.
Related standards
- ISO 500-2 (narrow-track tractors)
- ISO 500-3 (PTO dimensions and spline geometry)
- ISO 5673-2 (PTO driveline usage and clearance)
- ISO 6489 (tractor drawbar/attachment interfaces)
- ISO 789-1 / OECD Code 2 (PTO power test methods)
For full technical details and official figures, consult the published ISO 500-1:2014 document from ISO.