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GB/T 39542.3-2025: Mechanical pencils for technical drawings - Part 3: Black leads - Bending strengths of HB leads
Status: Valid GB/T 39542.3: Evolution and historical versions
| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivered in | Standard Title (Description) | Status | PDF |
| GB/T 39542.3-2025 | English | 214 |
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Mechanical pencils for technical drawings - Part 3: Black leads - Bending strengths of HB leads
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GB/T 39542.3-2025
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| GB/T 39542.3-2020 | English | 114 |
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Mechanical pencils for technical drawings - Part 3: Black leads - Bending strengths of HB leads
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Basic data | Standard ID | GB/T 39542.3-2025 (GB/T39542.3-2025) | | Description (Translated English) | Mechanical pencils for technical drawings - Part 3: Black leads - Bending strengths of HB leads | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | Y50 | | Classification of International Standard | 97.180 | | Word Count Estimation | 10,175 | | Date of Issue | 2025-05-30 | | Date of Implementation | 2025-05-30 | | Older Standard (superseded by this standard) | GB/T 39542.3-2020 | | Issuing agency(ies) | State Administration for Market Regulation, China National Standardization Administration | GB/T 39542.3-2025: Mechanical pencils for technical drawings - Part 3: Black leads - Bending strengths of HB leads
---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
ICS 97.180
CCSY50
National Standard of the People's Republic of China
Replaces GB/T 39542.3-2020
Technical drawing mechanical pencil
Part 3.Bending strength of black lead core HB lead core
(ISO 9177-3.2022, IDT)
Released on 2025-05-30
2025-05-30 Implementation
State Administration for Market Regulation
The National Standardization Administration issued
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 3 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 39542.3-2020 "Mechanical pencils for technical drawing - Part 3.Bending strength of black lead HB lead"
Compared with GB/T 39542.3-2020, in addition to structural adjustments and editorial changes, the main technical changes are as follows.
--- The lead type has been changed (see 4.2, 4.2 of the 2020 edition).
This document is equivalent to ISO 9177-3.2022 "Mechanical pencils for technical drawing - Part 3.Bending strength of black lead HB".
Please note that some of the contents of this document may involve patents. The issuing organization of this document does not assume the responsibility for identifying patents.
This document was proposed by China Light Industry Federation.
This document is under the jurisdiction of the National Technical Committee for Standardization of Pen Manufacturing (SAC/TC378).
This document was drafted by. Harbin Tiantan Pencil Co., Ltd., Shangzhi Pearl Pen Co., Ltd., Foshan Sanshui Yongsheng
Huawen Stationery Co., Ltd., Beifa Group Co., Ltd., Heshan Jiayi Stationery Industrial Co., Ltd., Heilongjiang Taibi Stationery Co., Ltd.,
Shanghai Chenguang Stationery Co., Ltd. and Zhejiang Hongxing Stationery Co., Ltd.
The main drafters of this document. Zhang Xiaoliang, Jin Shuangxi, and Long Shuiyun.
The previous versions of this document and the documents it replaces are as follows.
---First published in 2020 as GB/T 39542.3-2020;
---This is the first revision.
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 quality of black lead for mechanical pencils suitable for technical drawing
Require.
--- 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 flexural strength.
Technical drawing mechanical pencil
Part 3.Bending strength of black lead core HB lead core
1 Scope
This document specifies the bending strength and test method of black lead with hardness grade HB for use in technical drawing mechanical pencils.
2 Normative references
This document has no normative references.
3 Terms and definitions
The following terms and definitions apply to this document.
ISO and IEC maintain terminology databases used for standardization at the following websites.
3.1
Bending strength
The lead core strength is obtained by measuring the lead core from bending to the breaking point using the prescribed test method and calculation formula.
4 Bending strength
4.1 General
The bending strength of HB lead cores used in mechanical pencils shall be tested in accordance with Chapter 5 and shall comply with the requirements of 4.2.
4.2 Bending strength of HB black lead of mechanical pencil
The bending strength (σ) should not be less than the corresponding value of each nominal diameter specified in Table 1.
Table 1 Bending strength of HB lead for mechanical pencils
Lead core type Nominal diameter/mm Minimum bending strength (σ)/MPa
Resin (P)
0.35a 240
0.5 190
0.7 160
1a 95
Clay (C) 2 70
a Usually, the pencils and packaging can be marked as 0.3 and 0.9.Users should note that the new standardized mark is fully applicable to the old mark.
For a mechanical pencil, the reverse is true, i.e. 0.35 and 1 correspond to 0.3 and 0.9 respectively.
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