GB/T 14349-2026Press brakes - Testing of the accuracy (English PDF)

Foreword

This document was issued on 30 July 2026 by the State Administration for Market Regulation; Standardization Administration of the PRC and takes effect on 1 February 2027.

It is a GB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies.

It is classified under ICS 25.120.10 and Chinese classification J 62.

The document runs to 15 pages. The identification, the dates, the classification and the table of contents on this page are taken from the cover and the printed contents of the standard itself.

This document was drafted in accordance with GB/T 1.1-2020 "Directives for standardization - Part 1: Rules for the structure and drafting of standardizing documents".

This document replaces GB/T 14349-2011 "Press brake - Testing of the accuracy". Compared with the 2011 edition, apart from structural adjustments and editorial changes, the main technical changes are as follows:

-- the conditions for the testing of the working accuracy have been changed and the length of the test piece extended (see Table 1; Table 1 of the 2011 edition);

-- the conditions for the testing of the working accuracy have been changed and the thickness of the test piece extended (see Table 2; Table 2 of the 2011 edition);

-- the longitudinal length and the tolerance for the flatness of the table surface have been changed (see Table 3; Table 3 of the 2011 edition);

-- the longitudinal length and the tolerance for the parallelism of the horizontal supporting surface of the upper die seating to the table surface have been changed (see Table 5; Table 5 of the 2011 edition);

-- the tolerance for the perpendicularity of the ram stroke to the table surface has been changed (see Table 7; Table 7 of the 2011 edition);

-- the bend angle of the test piece in the working accuracy test has been changed (see Table 8; 4.2.1.1 of the 2011 edition);

-- the bend straightness of the test piece in the working accuracy test has been changed (see Table 9; 4.2.2.1 of the 2011 edition).

Attention is drawn to the possibility that some elements of this document may be the subject of patent rights. The issuing body assumes no responsibility for identifying them.

This document was proposed by the China Machinery Industry Federation.

It is under the jurisdiction of the National Technical Committee on Forging Machinery of Standardization Administration of China (SAC/TC 220).

The drafting organisations include Ruitie Machine Tool (Suzhou), Jiangsu Yawei Machine Tool, Anhui Donghai Yuxiang Intelligent Equipment, Aike (Suzhou) Machinery, Tianshui Forging Machine Tool Group, Jinan Foundry and Metalforming Machinery Testing, Hubei Sanhuan Forging & Pressing Equipment, Zhejiang Longwei Electric, Ningbo Baoheng Bearing Parts, Guangdong Quanqi Machinery Equipment and Ningbo Jiangbei Shengya Machinery.

This document was first issued in 1993 as GB/T 14349-1993 and first revised in 2011; the present edition is the second revision.

The document carries eight figures and nine tables: the conditions of the working accuracy test by test piece length and by thickness, the longitudinal and transverse flatness of the table surface, the parallelism of the upper die seating surface and of the ram supporting surface to the table surface, the perpendicularity of the ram stroke to the table surface, and the bend angle and the bend straightness of the test piece.

1 Scope

GB/T 14349 specifies how the accuracy of a press brake is tested, the machine that bends sheet metal between a punch and a die. It sets out the inspection requirements and the conditions under which the working accuracy is checked, including the length and the thickness of the test piece, and then covers geometric accuracy, that is the longitudinal and transverse flatness of the table surface, the parallelism of the upper die seating surface and of the ram supporting surface to the table, and the perpendicularity of the ram stroke, followed by working accuracy, measured on actual bent test pieces for bend angle and bend straightness. The distinction matters commercially: a machine can pass every geometric check and still not hold a bend angle across a two-metre part. The 2026 edition replaces GB/T 14349-2011, extending the length and thickness of the test pieces and revising the tolerance tables for flatness, parallelism, perpendicularity, bend angle and bend straightness. For a machine builder or a buyer this is the acceptance protocol a Chinese contract refers to.

2 Normative references

The contents of the following documents constitute indispensable provisions of this document through normative reference in the text. For dated references, only the edition corresponding to that date applies. For undated references, the latest edition, including all amendments, applies.

GB/T 8170 Rules of rounding off for numerical values and expression and judgement of limiting values.

GB/T 10923-2009 Forging machines - General rules for the inspection of accuracy.

JB/T 15403 Press brakes - Terminology.

3 Terms and definitions

The terms and definitions given in JB/T 15403 apply to this document.

4 Inspection requirements

4.1 General requirements

4.1.1 Before the accuracy inspection, the installation level of the press brake shall be adjusted; it shall not exceed 0.20 mm/1000 mm in either the longitudinal or the transverse direction.

4.1.2 The inspection of geometric accuracy shall be carried out under no-load conditions.

4.1.3 The inspection of geometric accuracy shall be carried out both before the idle running test and after the load test.

4.1.4 The working accuracy shall be inspected after the load test.

4.1.5 During the accuracy inspection, no mechanism or part affecting the accuracy shall be adjusted.

4.1.6 The accuracy inspection and the measuring instruments and gauges used for it shall comply with GB/T 10923.

4.1.7 The order of the accuracy inspections in this document does not represent the actual order of inspection; for convenience the inspections may be carried out in any order.

4.1.8 Where the actual measured length is less than the length specified for the tolerance, the tolerance shall be converted in proportion to the actual measured length, and the converted result rounded to the micrometre in accordance with GB/T 8170.

4.1.9 The accuracy inspection of the press brake shall be carried out with all the single-operation functions working normally.

4.1.10 Where no working accuracy grade is stated, the inspection is carried out to accuracy grade III as specified in 5.2.

4.2 Conditions for the testing of the working accuracy

4.2.1 The length of the test piece shall comply with Table 1, which relates the test piece length to the length of the table, in five bands from tables of 2000 mm or less up to tables of more than 8000 mm.

4.2.2 The width of the test piece shall not be less than 100 mm. The clause continues with the thickness of the test piece, given in Table 2, and with the remaining conditions of the test.

5 Accuracy testing

Clause 5 is organised as follows: 5.1 Geometric accuracy; 5.2 Working accuracy.