Overview
ISO 19957:2021 - "Footwear - Test methods for heels - Heel pin holding strength" specifies a standardized laboratory method to measure the force required to pull a single heel pin out of a heel. The procedure is used both to evaluate the intrinsic heel pin holding strength of heel materials (using a standard heel pin and controlled insertion) and to assess heel nailing in commercial production. This method applies to plastics and wooden heels for women’s footwear; it is not suitable for heels made from layered fibreboard or leather, or for low plastics heels for men’s footwear.
Key topics and technical requirements
- Scope and applicability: Measures pull-out force for a single standard heel pin to determine heel pin holding strength and to evaluate production heel nailing.
- Apparatus:
- Tensile testing machine conforming to ISO 7500-1, class 2, range ~0–2 000 N, traverse 40 mm/min ± 10 mm/min.
- Standard heel pin (length 18 ± 0.5 mm, buttress diameter ≥ 1.9 mm, specified buttress flanks and spacing).
- Heel nailing machine, small clamp/slotted hook, 2 mm metal rod for mounting.
- Sampling & preparation:
- Lab specimens: typically 3 heels × 6 pins (or 4 heels × 4 pins); when testing made shoes, prepare equivalent specimens where possible.
- Insertion control: use cellulose discs during pin insertion to ensure correct pin depth (5–8 mm of pin remaining).
- Attachment: drill ≈Ø2 mm hole through heel (typically 20–25 mm from top) for anchoring; alternate clamping for narrow/stiletto stems.
- Test procedure:
- Pull pin approximately parallel to shaft; record maximum load at removal.
- Traverse rate: 40 mm/min ± 10 mm/min.
- Measure penetration depth (d) with fine wire; inspect interior for cavities or incorrect insertion.
- Obtain at least 12 valid pull-out results for material assessment.
- Result expression:
- Heel pin holding strength h (N/mm) = F / (d − 4), where F = max pull-out load (N), d = measured depth (mm). Report averages and individual values.
Applications and users
ISO 19957:2021 is used for:
- Quality control and incoming inspection by footwear manufacturers.
- Production monitoring of heel nailing processes.
- Laboratory testing and material comparison for R&D and product development.
- Compliance documentation and failure analysis by test laboratories, material suppliers, and retailers.
Typical users: footwear manufacturers, test laboratories, material engineers, product designers, quality assurance teams.
Related standards
- ISO 7500-1 - Calibration and verification of static uniaxial testing machines (tension/compression), referenced for tensile machine requirements.
- ISO 19957:2021 is the second edition, revising ISO 19957:2004.
Keywords: ISO 19957:2021, heel pin holding strength, footwear testing, heel test method, tensile testing machine, standard heel pin, heel nailing, plastics heels, wooden heels.