Foreword
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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard is a revision of QB/T 1024-2007 Black leads for mechanical pencils.
In addition to a number of editorial changes, the following technical changes have been made with respect to QB/T 1024-2007:
——The requirements and test methods of leads with nominal diameter of 1.3mm are added (see 3.2, Clause 4 and Clause 6);
——The item name of flexural strength is modified (see 4.2 and 6.2; 4.1 and 5.1 of Edition 2007);
——The requirements and test method for the migration element content in the leads are added (see 4.8 and 6.8);
——The environmental conditions are added (see Clause 5);
———The marking is modified (see 8.1; 7.1 and 7.2 of Edition 2007);
This standard was proposed by the China National Light Industry Council.
This standard is under the jurisdiction of National Technical Committee on Writing Instrument of Standardization Administration of China (SACTC 378).
The previous editions of this standard are as follows:
——QB/T 1024-2007;
——QB/T 1024-1991.
Black leads for mechanical pencils
1 Scope
This standard specifies the classification, requirements, test methods, inspection rules as well as marking, packaging, transportation and storage of black leads for mechanical pencils.
It is applicable to black leads for mechanical pencils (hereinafter referred to as “leads”).
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies.
GB/T 191 Packaging - Pictorial marking for handling of goods
GB/T 2828.1 Sampling procedures for inspection by attributes - Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection
GB/T 12654 Writing paper
GB 21027 Request in common use of security for student's articles
3 Product classification
3.1 According to the main bonding material used, the leads may be divided into two types (namely, “P” type and “C” type), “P type” means resin type graphite lead; while “C” type means clay type graphite lead.
3.2 Leads are divided into 7 types according to nominal diameter and 12 types according to hardness. See Table 1 for the nominal diameter and hardness corresponding to “P” type and “C type” leads.
Table 1 Corresponding nominal diameters and hardness marks for different leads
Type Nominal diameter/mm Hardness mark
P 0.35a, 0.5, 0.7, 1a, 1.3 and 1.4 6H, 5H, 4H, 3H, 2H, H, F, HB, B, 2B, 3B and 4B
C 2
a Lead package may be marked with 0.3 and 0.9 (if applicable).
4 Requirements
4.1 The diameter and length of leads shall meet those specified in Table 2.
Table 2 Diameter and length of leads In mm
4.2 The bending strength of leads shall meet those specified in Table 3.
Table 3 Bending strength of leads In MPa
4.3 The density (absorbance) of leads shall meet those specified in Table 4.
Table 4 Density (absorbance) of leads
4.4 The smoothness (coefficient of friction) of leads shall meet those specified in Table 5.
Table 5 Smoothness (coefficient of friction) of leads
4.5 The wear of leads shall meet those specified in Table 6.
Table 6 Wear of leads In mm/m
4.6 The curvature of leads shall not be greater than 0.5mm.
4.7 The appearance of leads shall be straight, round and smooth, and free from bend.
4.8 The migration element content in leads shall meet the requirements of GB 21027.
Foreword i
1 Scope
2 Normative references
3 Product classification
4 Requirements
5 Environmental conditions
6 Test methods
7 Inspection rules
8 Marking, packaging, transportation and storage
