EN 320 Particleboard and fibreboard Screw Axial Withdrawal Test

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EN 320 Standard | Axial Screw Pull-Out Resistance Test for Particleboard & Fibreboard | Our Compliant Testing Equipment

EN 320 Particleboards and fibreboards — Determination of resistance to axial withdrawal of screws is the official European test standard we fully support with our custom-built axial screw withdrawal testing machine.

This European norm defines a standardized laboratory test procedure to measure axial screw withdrawal resistance, also referred to as axial pull-out force, needed to pull calibrated standard screws out of particleboard, medium-density fibreboard (MDF) and high-density fibreboard (HDF) panels. Our universal testing machine paired with dedicated EN 320 screw pull-out fixtures delivers precise, repeatable force measurement that fully meets all specimen setup, axial loading and data recording rules laid out in EN 320.

Keywords: EN 320 screw withdrawal tester, axial screw pull-out test machine for MDF HDF particleboard, wood panel fastener resistance testing equipment, axial pull-out force test for fibreboard, EN 320 compliant UTM fixture, MDF screw holding strength measurement, European standard wood composite screw withdrawal test

Test Principle

The core principle is to measure the peak uniaxial tensile force needed to pull a standardized ST4.2 tapping screw axially out of conditioned particleboard/fibreboard specimens. Load is applied strictly parallel to the screw’s central axis without bending torque. Two test modes simulate real assembly scenarios:

Face withdrawal: Screw embedded vertically into the flat panel surface

Edge withdrawal: Screw embedded into vertical board edges (only boards ≥15 mm)

The maximum recorded force directly quantifies the panel’s screw holding capacity.

EN 320 Particleboard and fibreboard Screw Axial Withdrawal Test

Test Specimen Info

Item	Requirement
Sampling	Per EN 326-1 (sampling, cutting, inspection — Part 1)
Dimensions	Square (75 ± 1) mm side — note: ISO 27528 says "at least 75 × 50 mm rectangle," EN 320 fixes a square.
Quantity	5 test pieces per sample board
Conditioning	(20 ± 2)°C, (65 ± 5)% RH to constant mass (≤ 0.1% mass change over 24 h); test within 1 h of removal
Pilot hole	Ø (2.7 ± 0.1) mm, depth (19 ± 1) mm, drilled perpendicular at midpoints of one face + two adjacent edges (edges only if board ≥ 15 mm)

Test Equipment required for EN 320 Screw Withdrawal Test:

Universal Testing Machine	Applies increasing axial load to underside of screw headvia a stirrup; restrains test piece; measures max load to ±1% accuracy.
Screw withdrawal test fixture	Jig with central bore for face testing on boards thinner than 15 mm (prevents specimen bending during pulling).
Screw withdrawal test fixture	Standard open slot jig for boards ≥15 mm for both face and edge tests Mandatory clearance rule: No jig support within 15 mm of the embedded screw perimeter.
Stirrup fixture with parallel slot	Fits the screw shank to transfer pure axial tensile load to the screw head without lateral offset.

Key Test Parameters & Mandatory Test Stipulations

Pilot hole specification:

Pre-drilled pilot hole diameter: 2.7 ±0.1 mm; hole depth: 19 ±1 mm. Holes are drilled perpendicular to the test surface, at the geometric midpoint of the specimen face and adjacent vertical edges (edges only for ≥15 mm boards).

Embedment depth: Uniform 15 ±0.5 mm of complete screw thread buried into the panel for both face and edge tests.

Fixture clearance: Minimum 15 mm distance between jig supports and the embedded screw’s outer edge.

Loading speed: Constant crosshead movement rate of (10 ±1) mm/min until screw pull-out failure.

Data recording precision: Maximum withdrawal force recorded to the nearest 10 N.

Step-by-Step General Test Procedures of EN 320:

Step 1: Specimen Conditioning & Pilot Hole Drilling

After 24-hour interval weighing to reach constant mass, drill standard 2.7 mm diameter pilot holes at the centre of the specimen face, plus midpoints of two adjacent edges (only for boards ≥15 mm). All hole depth is controlled to 19 ±1 mm.

Step 2: Screw Insertion

Drive the ST4.2 reference screw into each pilot hole to achieve exactly 15 ±0.5 mm full thread embedment inside the panel substrate. For thin boards (<15 mm), the unthreaded screw tip extends through the board’s reverse side.

Step 3: Specimen Mounting & Positioning

Secure the specimen into the metal jig following two positioning rules:

a) No jig contact within 15 mm of the embedded screw;

b) Test surface is perfectly perpendicular to the axial pulling load direction.

For boards thinner than 15 mm, the central bore jig must be used to support the thin specimen and eliminate bending interference.

Step 4: Axial Load Application

Clamp the screw head under the machine’s stirrup fixture, apply tensile load at a steady crosshead speed of 10 ±1 mm/min along the screw central axis until the screw fully pulls free from the panel.

Step 5: Data Capture & Result Calculation

Record peak maximum load for each face and edge screw (edge test skipped for boards <15 mm). Calculate average withdrawal force across the 5 replicate specimens as the final test result for the panel grade.

Related Test Standard:

ASTM D1761	Standard Test Methods for Mechanical Fasteners in Wood and Wood-Based Materials
ISO 27528	Wood-based panels - Determination of resistance to axial withdrawal of screws
EN 1382	Timber Structures - Test methods - Withdrawal capacity of timber fasteners
GOST R 57176	Timber structures. Test methods for withdrawal capacity of timber fasteners
BS 6948	Methods of test for mechanically fastened joints in timber and wood-based materials
GB/T 17657	Test methods of evaluating the properties of wood-based panels (equivalent to ASTM D1037 domestic implementation standard)
ASTM D143	Small Clear Timber Specimen Mechanical Test Methods
ASME B18.6.1	Inch-Series Wood Screw Specification
ASTM D1037	Test Methods for Wood-Base Fiber and Particle Panel Materials

Industry Application Fields

EN 320 is the primary test standard for European wood composite supply chains:

European furniture & flat-pack cabinet manufacturing: Kitchen units, wardrobes, desks, ready-to-assemble furniture sold in EU/EEA markets

Construction interior sector: Particleboard/MDF wall panels, shelving, interior joinery, flooring underlay

Wood panel factory quality control: In-line production inspection, new board formulation R&D, batch release certification

Third-party EU testing laboratories & product certification bodies: Mandatory test for CE marking compliance of particleboard/fibreboard products

Raw material procurement: Material comparison for furniture manufacturers sourcing European wood panels

EN 320 vs ISO 27528 Quick Comparison

items	EN 320:2011	ISO 27528:2009
Scope	Particleboard + fibreboard only	All wood-based panels (includes plywood, OSB)
Screw	Fixed: ST 4.2 × 38 mm (EN ISO 1478)	Choice: application screwor Annex A reference screw
Specimen	(75 ± 1) mm square	≥ 75 × 50 mm rectangle
Thickness floor	Edge test ≥15 mm; face test <15 mm allowed w/ jig	Panel ≥15 mm (or glue up); face + edge both tested
Embedment	Fixed (15 ± 0.5) mm complete thread	Face ≥11 ± 0.5 mm; Edge ≥15 ± 0.5 mm
Pilot hole	Fixed Ø 2.7 ± 0.1 mm, depth 19 ± 1 mm	Per panel-maker / screw-maker / fallback rule
Loading	(10 ± 1) mm/min (fixed crosshead)	Rate such that F_maxin (60 ± 30) s
Results (thin)	<15 mm face → N/mm (÷ thickness)	Glue-up to 15 mm, no N/mm convention
Edge reporting	Mean of 2 edges per piece	Separate; orthogonal directions kept apart
Normative family	EN 326-1, EN ISO 1478	ISO 16999, ISO 9424, ISO 2074, ISO 17064

WDW Series Computer Control Electronic Universal Testing Machine made by UNITEDTEST range from 100N to 600KN load capacity with various models like single columns, table type, door frame type etc., is used to perform tension, compression, flexure/bending, shearing, peeling etc., test for metal and nonmetal specimens.

Screw withdrawal test fixture, also widely named screw pull-out jig execute the accurate maximum screw withdrawal resistance (screw holding strength) test results for furniture, construction timber and engineered wood labs. Conform with ASTM D1761, ISO 27528 stabdard,

Q1: What is the core purpose of EN 320:2011?

A1: EN 320:2011 is a European standard that defines a fixed, standardized test method to measure the maximum axial pull-out force needed to extract a specified ST4.2 tapping screw from particleboard and fibreboard (MDF/HDF). It evaluates two performance indicators: face screw withdrawal strength (for all board thicknesses) and edge screw withdrawal strength (only boards ≥15 mm thick). The test provides uniform mechanical data to assess screw holding capacity for European market compliance and product design.

Q2: What materials does EN 320 cover? Which panels are excluded?

A2: Covered: Particleboards and wood fibreboards (MDF, HDF) as defined in EN 309 and EN 316.

Excluded: OSB, plywood and other multi-layer engineered wood panels; these follow the global standard ISO 27528 instead of EN 320.

Q3: Why is the EN 320 test extremely important for particleboard and fibreboard manufacturers selling into the EU?

A3: Mandatory CE marking requirement: Particleboard and fibreboard placed on the European Economic Area (EEA) market must use EN 320 to demonstrate screw retention performance for CE certification, which is a legal market access prerequisite.

Unified cross-border testing benchmark: All EU member states follow identical fixed test parameters (standard screw, fixed pilot hole, consistent loading speed), eliminating inconsistent regional test results and enabling fair supplier comparison across Europe.

Predict end-product service life: Low screw withdrawal strength causes loose furniture joints, sagging shelves, or failed interior construction connections; EN 320 data quantifies this risk for designers.

Guide production optimisation: Factories adjust board density, resin content, fibre grading and pressing processes based on EN 320 results to upgrade screw holding performance of low-grade panels.

Support product specification compliance: Most European furniture and construction product standards reference EN 320 as the official test method for fastener retention performance.

Q4: What is the difference between face withdrawal and edge withdrawal in EN 320?

A4: Face withdrawal: Screw is inserted vertically into the flat surface of the specimen; this test is allowed for all board thicknesses.

Edge withdrawal: Screw is drilled perpendicular into the vertical edge of the panel; this test is only required for boards with thickness ≥15 mm.

In most cases, edge withdrawal strength is significantly lower than face withdrawal strength because panel edges have less uniform fibre compression and bonding, representing the weakest real-world screw installation position.

Q5: Can I use any regular wood screw for EN 320 testing, or is a fixed reference screw mandatory?

A5: A fixed standard screw is mandatory for all compliant EN 320 tests, no alternative screws are permitted for official certification:

Screw model: ST 4.2 × 38 mm tapping screw complying with EN ISO 1478

Thread pitch: 1.4 mm

Required embedded full thread length inside the panel: 15 ±0.5 mm

For thin boards (<15 mm), the incomplete threaded tip of the screw must protrude fully through the opposite side of the test piece.

Q6: What are the fixed mandatory pilot hole dimensions for EN 320?

A6: The pilot hole size is strictly defined with no flexibility:

Diameter: 2.7 ± 0.1 mm

Drilling depth: 19 ± 1 mm

Holes must be drilled perpendicular to the test surface at the midpoint of the specimen face, and midpoints of two adjacent edges (only for boards ≥15 mm).

Q7: How many test specimens are required for a valid EN 320 test batch?

A7: A minimum of 5 square test pieces shall be sampled and cut from each board, following sampling rules in EN 326-1. Five replicates reduce random test deviation and ensure statistically reliable average withdrawal force results. Each specimen is a square with side length 75 ± 1 mm.

Q8: What loading speed is specified for pulling screws in EN 320? How to record results?

A8: Crosshead movement rate: Constant (10 ± 1) mm/min until the screw pulls out completely.

Maximum withdrawal force shall be recorded to the nearest 10 N for each individual screw test.

Final result is the average peak load from all 5 replicate specimens for face and edge tests separately.

Q9: What is the 15 mm clearance rule in EN 320 positioning? Why is it required?

A9: The jig and support structure cannot make contact with the test piece within 15 mm of the outer perimeter of the embedded screw thread.

This rule avoids artificial stress concentration caused by jig compression against the panel near the screw, which would falsely raise or lower the measured pull-out force and create unrepeatable, inaccurate test data.

Q10: What will happen if my panel fails EN 320 screw withdrawal testing?

A10: The product cannot obtain valid CE marking and cannot be legally sold to EU/EEA markets.

Furniture manufacturers will reject the panel batch due to risk of joint failure during assembly and long-term use.

Manufacturers must adjust production parameters (density, resin, pressing time) and re-test to meet the required minimum withdrawal force thresholds defined in European product standards.

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