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D4704-13 – Standard Test Method Technical Guide
📐 Specimen Geometry, Sampling, and Conditioning Requirements
The ASTM D4704-13 test method establishes a standardized procedure for determining the tongue tear strength of finished leather by measuring the force required to propagate a tear through a specimen cut perpendicular to its surface.
Unless otherwise specified, leather must be sampled in accordance with Practice D2813. The specimen itself is a precisely cut rectangle measuring 1 in. × 4 in. (25.4 mm × 101.6 mm) at the full thickness of the leather. A 3⁄16 in. (4.76 mm) diameter hole is located on the longitudinal axis, exactly 1 in. (25.4 mm) from one end. The specimen is then split longitudinally from the hole to the unsplit end, creating two distinct tongues. The orientation of the long axis relative to the backbone must be recorded (Section 6.2).
Prior to testing, all specimens must be conditioned in the atmosphere described in Practice D1610.
⚙️ Test Procedure and Apparatus Specifications
The testing machine must conform to the requirements detailed in Test Method D2209. The thickness of the specimen is determined using a dead-weight thickness gauge as described in Test Method D1813.
Thickness is measured to the nearest 0.001 in. (0.01 mm) along the long axis between the hole and the unsplit end. The gauge foot must be adjacent to the hole but must not overlap it (Section 8.1).
For the test, one tongue is clamped securely in each grip. The long axis of each tongue must align in the direction of motion of the movable grip. The grip faces must be positioned approximately 2 in. (50.8 mm) from the hole, which represents the common base of the two tongues (Section 8.2).
📊 Measured Properties and Their Significance
The primary result is the Tongue Tear Strength, defined in Section 3.1.1 as the load required to tear the leather between the tongues. Understanding the tearing strength of the sample is a critical factor in determining the suitability of the material for its intended end use (Section 4.1). Results are reported in accordance with the standard units stipulated in Section 1.2, where inch-pound units are regarded as standard.
| 🟦 Physical Configuration | 📐 Requirement |
|---|---|
| Specimen Dimensions | 1 in. × 4 in. (25.4 mm × 101.6 mm) |
| Hole Diameter | 3⁄16 in. (4.76 mm) |
| Hole Position from End | 1 in. (25.4 mm) |
| Grip Distance from Hole | ~2 in. (50.8 mm) |
| 🎯 Measurement & Process | ⚡ Standard |
|---|---|
| Thickness Precision | 0.001 in. (0.01 mm) |
| Thickness Gauge Type | Dead-weight (D1813) |
| Conditioning Practice | D1610 |
| Sampling Practice | D2813 |
⚠️ Important Scope Limitation: Per Section 1.1, this test method is intended for determining the tearing strength of leather and specifically does not apply to wet blue.
💡 Procedural Guidance: When measuring thickness per Section 8.1, ensure the gauge foot is placed adjacent to, but does not overlap, the 3⁄16 in. hole. This prevents erroneous measurements due to edge deformation or hole geometry.
❓ Frequently Asked Questions
🔍 What is the formal definition of Tongue Tear Strength?
It is defined in Section 3.1.1 as the load required to tear the leather between the two tongues formed by splitting the leather perpendicular to its surface.
💡 Can this standard be