Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D1814-70 – Standard Test Method Technical Guide
📐 Apparatus and Gage Requirements
The ASTM D1814-70 (Reapproved 2021) standard specifies two types of gages for measuring leather unit thickness: a spring-type gage and a standard wedge-type gage. The spring-type gage features a flat presser foot and anvil with a diameter of 0.4 ± 0.025 inches (10.2 ± 0.6 mm) and a spring that exerts a force of 1 lbf at a reading of 2 ounces and 2 lbf at a reading of 12 ounces. The wedge-type gage has legs graduated alternatively from 1 to 14 and 1½ to 13½ irons, with an enclosed angle of about 4° and a thickness of 0.425 ± 0.005 mm, preferably made from stainless steel. These gages enable rapid measurement for quality control and specification conformance.
| 🟦 Gage Type | 📏 Parameter | 🎯 Specification |
|---|---|---|
| Spring-Type | Presser foot diameter | 0.4 ± 0.025 in (10.2 ± 0.6 mm) |
| Spring-Type | Spring force at 2 oz | 1 lbf (4.45 N) |
| Spring-Type | Spring force at 12 oz | 2 lbf (8.9 N) |
| Wedge-Type | Leg graduations | 1 to 14 and 1½ to 13½ iron |
| Wedge-Type | Angle between legs | ~4° |
| Wedge-Type | Leg thickness | 0.425 ± 0.005 mm |
Note: The spring-type gage is designed for rapid measurement of leather other than sole leather, while the wedge-type gage is specifically for sole leather thickness in irons.
⚙️ Test Procedure and Measurement Requirements
For leather other than sole leather, the test specimen must be the full unit. Position the leather between the anvil and presser foot of the spring-type gage, ensuring full contact with the anvil. Compress the thumb lever until the gage reads approximately 15 ounces, then release it to allow the presser foot to snap onto the leather. Record the thickness to the nearest 0.1 mm or estimate to the nearest ¼ ounce. Repeat this measurement at no less than five equally spaced locations along and approximately 6 inches (150 mm) from the backbone of the unit. For sole leather, the wedge-type gage is used to measure thickness directly in irons according to the gage’s graduations.
Tip: Ensure measurements are taken at the specified distance from the backbone to standardize results and avoid edge effects.
📊 Units, Conversions, and Reporting Standards
Thickness measurements of leather units can be reported in millimetres, ounces, or irons. The standard mandates that inch-pound units are regarded as standard, with SI units provided for information. Common conversions include: 1 ounce = 1/64 inch (0.0156 in) = 0.396 mm, and 1 iron = 1/48 inch (0.0208 in) = 0.53 mm. Ounces are typically used for shoe upper leather, while irons are used for sole leather. Proper unit selection is critical for specification compliance and industry communication.
| 📐 Unit | ⚡ Equivalent in Inches | 📏 Equivalent in mm |
|---|---|---|
| 1 Ounce | 1/64 in (0.0156 in) | 0.396 mm |
| 1 Iron | 1/48 in (0.0208 in) | 0.53 mm |
Important: Always report the unit used for thickness measurements. For specification conformance, ensure conversion accuracy when comparing values in different units.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D1814-70? This test method covers the measurement of thickness of units of all types of leather but is not suitable for measuring test specimens.
💡 How are measurements taken with the spring-type gage? The leather is placed between the anvil and presser foot, the lever is compressed to 15 oz and released, and the thickness is read to 0.1 mm or ¼ oz, with at least five measurements along the backbone.
⚡ What are the standard units for leather thickness? Thickness can be reported in millimetres, ounces (for shoe upper leather), or irons (for sole leather), with defined conversions.
📌 What apparatus is required for this test? A spring-type gage for non-sole leather and a wedge-type gage for sole leather, each with specific dimensions and graduations as detailed in the standard.