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D1694-95 – Standard Test Method Technical Guide
📐 Thread Geometry and Form
This specification establishes the geometric requirements for a dedicated 60° stub thread system designed specifically for fiberglass (glass-fiber-reinforced thermosetting-resin) pipe. As defined in the standard, fiberglass pipe is a tubular product containing glass fiber reinforcements embedded in or surrounded by cured thermosetting resin. The composite structure may contain aggregate fillers, thixotropic agents, pigments, or dyes, and may include thermoplastic or thermosetting liners or coatings. The thread form follows the American National Standard 60° stub thread geometry, as modified and strictly defined by the specific figures and tables within this document.
Regarding assembly, the male thread may be preceded by a cylindrical pilot. The pilot length must equal exactly two thread pitches, and its outside diameter must be equal to or less than the theoretical thread diameter if the thread were extended to the end of the pilot. The geometry of the gages used to inspect this thread is also defined in detail, with the gage form conforming to Fig. 2 of the standard and tolerances listed in the relevant tables.
📏 Dimensional Specifications and Tolerances
The specification governs pipe sizes from 1½ to 20 inches in diameter. All sizes within this range are required to have a consistent thread configuration of exactly 8 threads per inch. The thread is required to have a taper of 1 in 32 on the diameter. The fundamental pitch is uniformly specified at 0.125 inches (3.175 mm).
Precision in manufacturing is critical for proper thread engagement. The standard imposes strict tolerances on the thread lead: ±0.003 inches per inch of thread length, with a cumulative lead tolerance of ±0.006 inches. The theoretical dimensions for the pipe thread are detailed in Table 1 of the standard, while the dimensions and tolerances for the required gaging are detailed in Tables 2 and 3.
| 🟦 Thread Configuration Parameter | 📏 Specification |
|---|---|
| Applicable Pipe Diameter Range | 1½ to 20 inches |
| Required Thread Count | 8 threads per inch |
| Fundamental Thread Pitch | 0.125 in (3.175 mm) |
| Thread Taper (on Diameter) | 1 in 32 |
| Thread Form Angle | 60° Stub |
| Lead Tolerance (Per Inch) | ±0.003 in (±0.076 mm) |
| Lead Tolerance (Cumulative) | ±0.006 in (±0.152 mm) |
🔬 Precision of Measurement
The standard provides specific indexes of precision for the measurement of these threads, based on documented industry experience and defined as a 2S value in strict accordance with Practice E 177.
Two primary measurement methods are formally recognized. The multi-operator-specimen-day precision for a standard micrometer caliper is established at ±0.001 inches (0.025 mm). Similarly, a single-optical comparator with micrometer head readout, evaluated under the same multi-operator-specimen-day conditions, also demonstrates a precision of ±0.001 inches (0.025 mm).
| 🎯 Measurement Tool / Method | ⚡ Index of Precision (2S) |
|---|---|
| Micrometer Caliper | ±0.001 in (0.025 mm) |
| Optical Comparator with Micrometer Head Readout | ±0.001 in (0.025 mm) |
⚠️ No International Equivalent: As explicitly stated in the standard (Note 1), there is no similar or equivalent ISO standard for this 60° stub thread system. Products manufactured to ASTM D1694 are unique to this specification and require dedicated gaging that exactly conforms to the standard’s figures and dimensional tables.
💡 Primary Units: It is a controlling requirement of this specification that the values stated in inch-pound units are to be regarded as the standard. Any values provided in parentheses (e.g., millimeters) are for informational purposes only and do not represent the primary standard for compliance.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D1694?
ASTM D1694 specifically covers the geometry and dimensions of a tapered 60° stub thread system designed for glass-fiber-reinforced thermosetting-resin pipe, commonly referred to as fiberglass pipe.
💡 What are the key dimensional requirements for the thread?
The standard mandates 8 threads per inch with a fundamental pitch of 0.125 inches. The thread must have a taper of 1 in 32 on the diameter. Strict lead tolerances of ±0.003 inches per inch and ±0.006 inches cumulative are required.
⚡ How is measurement precision established for this standard?
The standard follows Practice E 177 and defines precision using a 2S index. For both a micrometer caliper and an optical comparator with a micrometer readout head, the multi-operator-specimen-day precision is ±0.001 inches (0.025 mm).
📌 Are there ISO equivalents for this 60° stub thread?
No. Per Note 1 embedded in the standard, there is no similar or equivalent ISO standard. This specific 60° stub thread is a unique American National Standard tailored for fiberglass pipe systems and requires dedicated gaging.