GB/T 1804-2000General tolerances - Tolerances for linear and angular dimensions without individual tolerance indications (English PDF)

Foreword

This Standard is formulated through amendment made to GB/T 1804-1992 "General

tolerance - Tolerances for linear and angular dimensions without individual tolerance

indications" and GB/T 11335-1989 "Limit deviations of angle without tolerance

indication" according to the international standard ISO 2768-1.1989 "General tolerance

- Part 1.Tolerances for linear and angular dimensions without individual tolerance

indications". It shall be technically equivalent to this Standard.

In this way, it shall enable the general tolerance standard for dimensions without

individual tolerance indications of China to be as identical or equivalent to the

international standard as possible, so as to adapt to the international trade,

technological and economic exchanges, as well as the demands for adoption of

international standards for rapid development.

In comparison with the original GB/T 1804 and GB/T 11335, this Standard has added

4 clauses, namely normative reference, definitions, general principles and

determination, and also changed the title of the standard.

This Standard has replaced GB/T 1804-1992 and GB/T 11335-1989 from the date of

implement.

Annex A of this Standard is an informative annex.

This Standard is proposed by State Bureau of Machine Building Industry.

This Standard shall be under the jurisdiction of National Technical Committee of

Standardization for Geometrical Production Specification and Verification.

Drafting organization of this Standard. Mechanical Engineering Research Institute.

Main drafters of this Standard. Li Xiaopei and Yu Hanqing.

1 Scope

This Standard specifies tolerance classes and limit deviations of general tolerances for

linear and angular dimensions without individual tolerance indications.

This Standard applies to the dimensions of parts that are produced by metal removal,

it also applies to the dimensions of parts that are formed from sheet metal. The

dimensions of non-mental materials or other process method may also reference to

this Standard.

This Standard only applies for the following dimensions which do not have an individual

tolerance indication.

a) linear dimensions (e.g. external sizes, internal sizes, step sizes, diameters,

radius, distances, rounding radius and chamfer heights);

b) angular dimensions, including angular dimensions usually not indicated, e.g.

right angles (90°); excluding the angles as mentioned in GB/T 1184, or angles

of uniform polygons;

c) linear and angular dimensions produced by machining assembled parts.

This Standard does not apply for the following dimensions.

a) linear and angular dimensions which are covered by reference to other

standards on general tolerances;

b) auxiliary dimensions indicated in brackets;

c) theoretically exact dimensions indicated in rectangular frames.

2 Normative references

The following standards contain provisions which, through reference in this text,

constitute provisions of this Standard. At the time of publication, the editions indicated

were valid. All standards are subject to revision, and parties to agreements based on

this Standard are encouraged to investigate the possibility of applying the most recent

editions of the standards indicated below.

GB/T 1800.1-1997 Limits and fits - Bases - Part 1.Terminology

GB/T 1184-1996 Geometrical tolerancing - Geometrical tolerances for features

without individual tolerance indications (eqv ISO 2768-2.1989)

GB/T 4249-1996 Tolerancing principle (eqv ISO 8015.1985)

GB/T 6403.4-1986 Rounding and chamfered of parts

3 Definitions

4 General principles

When selecting the tolerance class of the general tolerance for dimensions without

individual tolerance indications on drawings, the respective customary workshop

accuracy shall be taken into consideration and the corresponding technical documents

or standards shall give specific specifications.

5 Tolerance class and limit deviations of general tolerances

General tolerances are divided into 4 classes, namely fine f, medium m, coarse c and

very coarse v. Corresponding tolerance class and limit deviation are given according

to linear and angular dimensions without individual tolerance indications

6 Method for general tolerance indication on drawings

If general tolerances in accordance with this Standard shall apply, the number of this

Standard and the code of tolerance class shall be indicated near the title block on

drawings or in technical requirements and technical documents (such as industrial

standards). For example, when medium class is selected, it shall be indicated as the

following.

7 Determination

Unless otherwise stated, workpieces exceeding the general tolerance shall not lead to

automatic rejection provided that the ability of the workpiece to function is not impaired

(see clause A.5).

Annex A

(Informative)

Concepts behind general tolerance of linear and angular dimensions

A.1 All features on component parts always have a size and a geometrical shape. For

the deviation of size and for the deviations of the geometrical characteristics (form,

orientation and location) the function of the part requires limitations which, when

exceeded, impair this function. Therefore, certain tolerance requirements shall be

given when all features on component parts are indicated on drawings.

For features having no special requirement for functions, the general tolerances may

be given. The general tolerances can be applied in geometrical elements such as linear

dimensions, angular dimensions, form and location.

For features adopting general tolerances, it is not necessary to indicate the tolerance

separately on the drawings, but to give general explanations in the drawings, technical

requirements or technical documents (such as industrial standards).

A.2 The general tolerances of linear and angular dimensions are the tolerance that can

be guaranteed by machine tool equipment under normal process conditions in

workshops. Under normal maintenance and operation, it represents the customary

processing accuracy of workshops.

The tolerance value for the tolerance class of general tolerances shall comply with the

customary workshop accuracy. It shall select the corresponding tolerance class

according to the service requirements of component parts.

The general tolerances of linear dimensions are mainly used for low-accuracy unfitting

dimensions.

The inspections on the dimensions adopting general tolerances can usually be omitted

under the condition that the customary workshop accuracy is guaranteed.

A.3 Above certain tolerance values, there is usually no gain in manufacturing economy

by enlarging the tolerance. For example, a feature having a 35 mm diameter could be

manufactured to a high level of conformance in a workshop with "customary medium

accuracy". Specifying a tolerance of ± 1 mm would be of no benefit in this particular

workshop, as the general tolerance values of ± 0.3 mm would be quite adequate.

In cases where the function of a feature allows a tolerance equal to or larger than the

general tolerance values, it shall adopts general tolerances. Only when the function of

the feature allows a larger tolerance than the general tolerances, and the larger

tolerance will provide manufacturing economy (e.g. the depth of blind holes drilled at

assembly), the corresponding limit deviation shall be indicated individually adjacent to

the dimension.

However, if, for functional reasons, a feature requires a smaller tolerance value than

the "general tolerances", then corresponding limit deviations shall be indicated

individually adjacent to the dimension. This type of tolerance falls outside the scope of

general tolerances.

A.4 Using general tolerances leads to the following advantages.

A.5 The tolerance the function allows is often greater than the general tolerance. The

function of the part is, therefore, not always impaired when the general tolerance is

(occasionally) exceeded at any feature of the workpiece. Exceeding the general

tolerance should lead to a rejection of the workpiece only if the function is impaired.

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