ISO 2857:1973/Amd 2:1986

Overview

ISO 2857:1973/Amd 2:1986 is an important amendment to the original ISO 2857:1973 standard, focusing on ground thread taps for ISO metric threads. Specifically, this amendment addresses the manufacturing tolerances on the threaded portion of taps designed for ISO metric threads with tolerances ranging from 4H to 8H and 4G to 6G. It covers both coarse and fine pitch thread types, ensuring precision and consistency in the production of cutting tools used in thread making.

Published by the International Organization for Standardization (ISO) in 1986, this amendment provides critical updates to measurement methods and tolerance values, promoting enhanced quality control and performance in thread tapping operations.

Key Topics

• Ground Thread Taps: Precision tools used for cutting ISO metric threads, designed to strict tolerances for smooth and accurate thread formation.
• Tolerance Classes 4H to 8H and 4G to 6G: Defines the acceptable dimensional variations for internal threads of various fit classes including both coarse and fine pitch threads.
• Manufacturing Tolerances on Threaded Portion: Specifies the permissible deviations on the threaded portion of the taps to ensure the quality and interchangeability of the threads produced.
• Pitch Tolerance Specifications:
  • Tolerance based on equivalent diametral error on pitch.
  • Measurement over a length of 7 thread pitches, correlating with the typical engagement length.
  • For thread pitches smaller than 1.5 mm, the measurement length is adjusted to approximately 50% of the total threaded length of the tap to allow compatibility with standard measurement practices.
• Updated Measurement and Tolerance Methods:
  • Amendment updates paragraph 4.5 on pitch tolerance.
  • Provides refined definitions that support industry-standard measuring procedures for thread taps.

Applications

ISO 2857:1973/Amd 2:1986 is highly relevant for manufacturers, quality control engineers, and technical designers involved in:

• Cutting Tool Production: Ensures factory-made ground thread taps meet international precision standards.
• Threaded Fastener Manufacturing: Supports the consistent production of threaded parts with reliable fits, particularly where ISO metric threads are employed.
• Quality Assurance and Inspection: Offers a clear framework for tolerance verification, helping reduce rejection rates and improving final product reliability.
• Mechanical Engineering and Assembly: Guarantees threading tools produce accurate threads, crucial for assembly tightness, wear resistance, and mechanical strength in machinery.
• Tool Standardization Efforts: Facilitates global harmonization of thread manufacturing standards, ensuring interchangeability across diverse markets and applications.

Related Standards

For complementary understanding and application, the following ISO standards are commonly associated with ISO 2857:1973/Amd 2:1986:

• ISO 965-1: Specifies general tolerances for ISO metric screw threads, including tolerance classes and pitch diameter limits.
• ISO 261 / ISO 262: Define the fundamental ISO metric thread profiles and series of preferred sizes.
• ISO 529: Covers tools for thread cutting – taps and dies.
• ISO 1502: Details the designation system for ISO metric screw threads.
• ISO 286: Provides guidance on fits and tolerances for mating parts, particularly useful in combination with thread standards.

Conclusion

ISO 2857:1973/Amd 2:1986 strengthens the quality framework for ground thread taps used in producing ISO metric threads by refining manufacturing and measurement tolerances. This amendment is essential for industries relying on accurate and reliable threading tools to maintain product consistency and performance. Adherence to these specifications enhances tool life, product interchangeability, and assembly integrity across various engineering and manufacturing sectors.