Overview
ISO 20168:2016 - Resistance welding - Locking tapers for electrode holders and electrode caps specifies the geometric dimensions and tolerances for spot‑welding electrode holders and electrode caps that use a locking taper (traditionally called a Fisher taper). The standard ensures consistent fit, interchangeability and reliable electrical/mechanical contact where the cap engages the holder.
Key topics and requirements
- Scope: Defines dimensions and tolerances for electrode holders and spot‑welding electrode caps when a locking taper is used.
- Locking taper definition: A taper that produces a tight fit between holder and cap; the standard notes the taper angle relationship (document reference: difference in taper angles as given in the standard) and shows the engagement point at the skirt of the cap.
- Specified taper angles:
- Electrode holders: 2° 58′ 54″
- Electrode caps: 2° 56′ 53″
- Dimension sets: Table 1 provides recommended dimensions (and recommended maximum electrode force depending on cap hardness) for commonly used nominal sizes - 13 mm, 16 mm and 20 mm.
- Designation rules:
- Electrode holders: designated as ISO 20168 – [nominal diameter] (example: ISO 20168 – 20).
- Electrode caps: designated per ISO 5821 but prefixed with ISO 20168 to indicate a locking taper cap (example format shown in the standard).
- Material and marking:
- Materials to be used are referenced to ISO 5182 (materials for electrodes and ancillary equipment).
- Packaging must be marked with full designation and material used.
- Normative references include ISO 5182, ISO 5821 and ISO 17677‑1; bibliography cites related GPS and taper standards.
Applications
- Standardizes manufacturing and inspection of spot welding electrode holders and caps for resistance welding equipment.
- Ensures interchangeability of parts from different suppliers, reducing machine downtime and simplifying spare‑parts inventory.
- Improves mechanical stability and electrical contact reliability in spot welding operations where a locking taper is used.
- Useful for quality control, dimensional inspection, tooling design and procurement specifications.
Who should use this standard
- Welding equipment and electrode cap manufacturers
- Welding engineers, production and maintenance teams in automotive, appliance and metal fabrication industries
- Quality assurance teams, purchasing/specification writers and standards/ compliance personnel
Related standards
- ISO 5182 - Materials for electrodes and ancillary equipment
- ISO 5821 - Spot welding electrode caps
- ISO 17677‑1 - Resistance welding vocabulary (spot, projection and seam welding)
Keywords: ISO 20168:2016, resistance welding, locking taper, electrode holders, electrode caps, spot welding, dimensions and tolerances, welding standards, Fisher taper.
