Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 6414-1999 Castings - System of Dimensional Tolerances and Machining Allowances. The following technical changes have been made with respect to GB/T 6414-1999.
——Part dimensional tolerances for castings are modified;
——Generally attainable tolerance grades for various alloy castings in mass production as specified in Table A.1 are modified;
——"Table 1 Abbreviations" is added;
——Tables 3~7 are added;
——Tolerance grades in Table A.1 and Table A.3 are modified;
——Original Annex C is deleted and new Annexes C, D and E are added.
This standard has been redrafted and modified in relation to ISO 8062-3:2007 Geometrical Product Specifications (GPS) - Dimensional and Geometrical Tolerances for Moulded Parts - Part 3: General Dimensional and Geometrical Tolerances and Machining Allowances for Castings.
This standard is adjusted largely in structure with respect to ISO 8062-3:2007; the comparison table for chapter and article numbers between this standard and ISO 8062-3:2007 is listed in Annex E.
The technical differences between this standard and ISO 8062-3:2007 as well as their reasons are as follows:
——Nominal dimension of casting and figures are added in "Chapter 3 Terms and Definitions";
——"Chapter 4 Dimensioning" is added;
——"Chapter 5 Tapered Features" is added;
——Illustrations for machining allowance in Chapter 10 are added.
The following editorial changes have been made in this standard:
——This standard is renamed as "Castings - Dimensional Tolerances and Geometrical Tolerances and Machining Allowances".
This standard was proposed by and is under the jurisdiction of the National Technical Committee on Foundry of Standardization Administration of China (SAC/TC 54).
The previous editions of this standard are as follows:
——GB/T 6414-1986; GB/T 6414-1999.
Castings - Dimensional Tolerances and Geometrical Tolerances and Machining Allowances
1 Scope
This standard specifies those requirements for castings including terms and definitions of dimensional tolerance, geometrical tolerance and machining allowance as well as dimension indication method, dimensional tolerance grade, geometrical tolerance grade, required machining allowance grade and the indications on the drawing.
It is applicable to castings produced by various casting methods.
2 Normative References
The following documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the normative document (including any amendments) applies.
GB/T 131 Geometrical Product Specifications (GPS) - Indication of Surface Texture in Technical Product Documentation
GB/T 1182 Geometrical Product Specifications(GPS) - Geometrical Tolerancing - Tolerances of Form, Orientation, Location and Run-out
GB/T 1800.1 Geometrical Product Specifications (GPS) - Limits and Fits - Part 1: Bases of Tolerances, Deviations and Fits
GB/T 1800.2 Geometrical Product Specifications (GPS) - Limits and Fits - Part 2: Tables of Standard Tolerance Grades and Limit Deviations for Holes and Shafts
GB/T 4458.5 Mechanical Drawings - Indication of Tolerances for Size and of Fits
GB/T 5611 Foundry Terminology
GB/T 16892 Geometrical Tolerancing Indication of Non-rigid Parts
GB/T 17851 Geometrical Product Specifications (GPS) - Geometrical Tolerancing - Datums and Datum System
GB/T 24744 Geometrical Product Specifications (GPS) - Drawing Indications for Moulded Parts in Technical Product Documentation (TPD)
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 5611 and the followings apply.
3.1
nominal dimension of casting
design dimension of a rough casting before machining (see Figure 1), including the necessary machining allowance (see Figure 2)
Figure 1 Drawing Indications
Figure 2 Dimensional Tolerances and Limit of Dimension
3.2
dimensional casting tolerance
allowable variation value of casting dimension. The tolerance is equal to the absolute value of the difference between the maximum limit of dimension and the minimum one and it is also equal to the absolute value of the difference between the upper deviation and the lower one
3.3
surface mismatch (shift)
mismatch of joint faces of different casting parts due to misplacement in the mould closing
3.4
required machining allowance; RMA
reserved metal allowance on rough casting to eliminate the influence of casting on the surface by subsequent machining and to obtain the desired characteristic and the necessary dimensional precision
3.5
draft
taper on mould or core box parallel to the pattern drawing direction, for facilitating the removal of a mould from a casting mould, or a core from a core box
4 Dimensioning
With the exception of dimensioning of wall thickness (where a dimensional chain composed of two dimensions is allowable), chain dimensioning shall be avoided.
5 Tapered Features
5.1 Where the design requires the position for a taper (if any draft), the tolerance symmetrically distributed along the surface shall be adopted (see Figure 3).
5.2 Generally, increasing materials, decreasing materials or taking the average in the drawing shall be specified on the taper, which are expressed as taper + [Figure 3 a)], taper – [Figure 3 b)] and taper ± [Figure 3 c)] correspondingly.
5.3 Special surface draft which is differ from the general draft arrangement in the drawing shall be separately indicated on the surface and the indication shall be in accordance with GB/T 131; for example .
5.4 For dimensions required machining, "draft +" shall be adopted, irrespective of the general technical requirements for draft, in order to obtain the final dimension.
Foreword i
1 Scope
2 Normative References
3 Terms and Definitions
4 Dimensioning
5 Tapered Features
6 Abbreviations
7 Tolerance Grades
8 Surface Mismatch (SMI)
9 Wall Thickness Tolerance
10 Required Machining Allowance (RMA)
11 Indication on Drawings
Annex A (Normative) Casting Tolerance
Annex B (Informative) Application of General Geometrical Tolerances for Castings
Annex C (Informative) Datums for General Geometrical Tolerances
Annex D (Normative) Required Machining Allowance Grade (RMAG)
Annex E (Informative) Comparison for Chapter and Article Numbers Between this Standard and ISO 8062-3:
