GB/T 39542.2-2025Mechanical pencils for technical drawings - Part 2: Black leads - Classification and dimensions (English PDF)

Foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for standardization work Part 1: Structure and drafting rules for standardization documents" Drafting.

This document is Part 2 of GB/T 39542 "Mechanical pencils for technical drawing". GB/T 39542 has published the following parts.

--- Part 1: Classification, dimensions, performance requirements and tests;

--- Part 2: Classification and dimensions of black lead cores;

--- Part 3: Bending strength of black lead core HB lead.

This document replaces GB/T 39542.2-2020 "Mechanical pencils for technical drawing - Part 2: Classification and dimensions of black lead cores" Compared with GB/T 39542.2-2020, in addition to structural adjustments and editorial changes, the main technical changes are as follows;

a) The definitions of black lead and hardness grade have been changed (see 3.1, 3.2, 3.1, 3.2 of the 2020 edition);

b) Change graphite lead core to clay lead core (see 3.1.2, 3.1.2 of the 2020 edition).

This document is equivalent to ISO 9177-2:2022 "Mechanical pencils for technical drawing - Part 2: Classification and dimensions of black lead cores". The following minimal editorial changes were made to this document.

--- A footnote is added to Table 2.

Introduction

Mechanical pencils are one of the most popular writing tools among consumers. Mechanical pencils are divided into general-purpose mechanical pencils according to different usage occasions. and technical drawing mechanical pencils to meet the evolving market needs. The third edition of ISO 9177-1 in 2016 changed the main elements of the standard name to The second edition of ISO 9177-2 and ISO 9177-3 in 2022 also made the same adjustment, and the technical content is only Limited to technical drawing mechanical pencils and their leads to distinguish them from general purpose mechanical pencils.

GB/T 39542 is intended to consist of three parts.

--- Part 1: Classification, dimensions, performance requirements and tests. The purpose is to establish the quality requirements for mechanical pencils suitable for technical drawing and test methods.

--- Part 2: Classification and dimensions of black lead. The purpose is to establish the basic qualities of black lead for mechanical pencils suitable for technical drawing. Quantity requirements.

--- Part 3: Bending strength of HB black lead. The purpose is to establish the HB black lead suitable for technical drawing mechanical pencils Requirements and test methods for core bending strength.

1 Scope

This document specifies the assortment and dimensions of black leads for mechanical pencils used for technical drawing.

This document applies to two types of black lead.

---Resin lead (marked with the letter "P");

---Clay lead (marked with the letter "C").

2 Normative references

The contents of the following documents constitute essential clauses of this document through normative references in this document.

For referenced documents without a date, only the version corresponding to that date applies to this document; for referenced documents without a date, the latest version (including all amendments) applies to This document.

ISO 128-2 Technical product documentation (TPD) General principles for drawing Part 2: Basic rules for drawing lines]

Note: GB/T 39542.1-2020 Mechanical pencils for technical drawing Part 1: Classification, dimensions, performance requirements and tests (ISO 9177-1:2016, IDT)

3 Terms and definitions

For the purposes of this document, the terms and definitions defined in ISO 9177-1 and the following apply.

ISO and IEC maintain terminology databases used for standardization at the following websites.