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GB/T 21471-2008: Machining allowances and tolerances for steel open die forgings on hammer -- Shafts Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedure Status: Valid
Similar standardsGB/T 21471-2008: Machining allowances and tolerances for steel open die forgings on hammer -- Shafts---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT21471-2008 GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA ICS 77.140.85 J 32 Replacing GB/T 15826.6~15826.9-1995 Machining Allowances and Tolerances for Steel Open Die Forgings on Hammer – Shafts Issued on. FEBRUARY 28, 2008 Implemented on. AUGUST 1, 2008 Issued by. General Administration of Quality Supervision, Inspection and Quarantine; Standardization Administration of the People’s Republic of China. Table of ContentsForeword... 3 1 Scope... 4 2 Normative References... 4 3 Shafts without Steps... 4 4 Shafts with Steps... 7 5 Single Throw Crankshaft... 12 6 Forgings without Machining... 14 Appendix A (Informative) Example of Calculation of the Size of Open Die of Shafts without Steps... 16ForewordThis Standard revised GB/T 15826.6-1995 Machining Allowances and Tolerances for Steel Open Die Forgings on Hammer - Shaft without Steps, GB/T 15826.7-1995 Machining Allowances and Tolerances for Steel Open Die Forgings on Hammer - Shaft with Steps, GB/T 15826.8-1995 Machining Allowances and Tolerances for Steel Open Die Forgings on Hammer - Single Throw Crankshaft, and GB/T 15826.9-1995 Machining Allowances and Tolerances for Steel Open Die Forgings on Hammer - Forging without Machining. The major revised contents are as follows. --- Integrate GB/T 15826.6-1995, GB/T 15826.7-1995, GB/T 15826.8-1995, and GB/T 15826.9-1995 into one standard. --- Add table of contents and foreword. --- Add normative references. --- Delete the calculation examples in Section 3.4 of GB/T 15826.6-1995, and its content is given as "Appendix A". The Appendix A of this Standard is informative. This Standard was proposed by China Machinery Industry Federation. This Standard shall be under the jurisdiction of National Technical Committee on Forging of Standardization Administration of China. Drafting organizations of this Standard. Shanghai Hudong Forging Factory; and Pinghu Chenren Meter Co., Ltd. Chief drafting staffs of this Standard. Sun Changfen, and Dong Zhusheng. The historical editions replaced by this Standard are as follows. --- GB/T 15826.6-1995; --- GB/T 15826.7-1995; --- GB/T 15826.8-1995; --- GB/T 15826.9-1995. Machining Allowances and Tolerances for Steel Open Die Forgings on Hammer – Shafts1 ScopeThis Standard specifies the machining allowances and tolerances of open die forgings such as shafts without steps, shafts with steps, and single throw crankshaft, as well as the allowable limit deviations of forging without machining. This Standard applies to open die forgings of carbon steel and alloy steel with a carbon content not exceeding 0.9% and a total content of other alloy components not exceeding 4%. For open die forgings that exceed the range specified in this Standard, the allowances and tolerances shall be determined by negotiation between the supplier and the purchaser.2 Normative ReferencesThe provisions in following documents become the provisions of this Standard through reference in this Standard. For dated references, the subsequent amendments (excluding corrigendum) or revisions do not apply to this Standard, however, parties who reach an agreement based on this Standard are encouraged to study if the latest versions of these documents are applicable. For undated references, the latest edition of the referenced document applies. GB/T 21469 Machining allowances and tolerances for steel open die forgings on hammer - General requirement JB/T 9179.2 Machining allowance and tolerance of open die forgings on hydraulic press - Round shaft, square shaft and rectangular cross-section JB/T 9179.3 Machining allowance and tolerance of open die forgings on hydraulic press - Stepped shaft3 Shafts without Steps3.1 The dimensions of open die forgings of the shafts without steps with round, square, hexagonal, octagonal or rectangular (B/H≤5) cross-section shall be L＞2.5D (or A, B, S). 3.2 The machining allowance and tolerance of open die forgings of the shafts without steps shall comply with the provisions of Figure 1 and Table 1. 3.3 General description 3.3.1 When the ratio of the length of the two sides of the rectangular cross-section shaft without step B/H >2.5, the allowance α of H increases by 20%. 3.3.2 When the part size L/D (or L/B) >20, the allowance α increases by 30%. 3.3.3 The rest shall comply with the provisions of GB/T 21469. 3.3.4 For the rectangular cross-section shaft without step, the larger side B and the length L are used to find α in Table 1 to determine the allowances of L and B. The allowance α of H is determined by looking up the length L and the calculated value Hp = (B+H)/2 in Table 1. 3.3.5 For the determination of the forging size of rectangular cross-section shaft without step, Unit. mm4 Shafts with Steps4.1 The ratio of the total length L of open die forging of shaft with step with the circular cross- section to the maximum step diameter D (L/D) shall be greater than 2.5. 4.2 The machining allowance and tolerance of open die forgings of shafts with steps shall comply with the provisions of Figure 2 and Table 2. 4.3 General description 4.3.1 The allowance on the diameter and length of each step is determined according to the Unit. mm 4.3.2 When the ratio of the total length L to the diameter Di on certain position of the part is greater than 20, the allowance of the diameter Di shall be increased by 30%. 4.3.3 When the ratio of two adjacent diameters of a part is greater than 2.5, the diameter allowance of one part can be increased by 20% according to the principle of saving materials. 4.3.4 Whether the steps and L gear are forged or not shall be determined in accordance with 4.4. 4.3.5 Whether the end flanges and intermediate flanges are forged or not shall be determined in accordance with 4.5. 4.3.6 The rest shall comply with the provisions of GB/T 21469. 4.4 Forging conditions of steps and L gear 4.4.1 The forging conditions of steps or L gear on forgings shall comply with the provisions of Figure 3 and Table 3. 4.4.2 When the end step length L1 ≥1, it shall be forged. 4.4.3 When the middle step length L2 ≥0.81, it shall be forged.5 Single Throw Crankshaft5.1 If the crank height H (or D) of single throw crankshaft and eccentric shaft open die forgings is ≤500 mm, the crank length L shall be ≤ 600 mm. 5.2 The machining allowance and tolerance of single throw crankshaft and eccentric shaft forgings shall comply with the provisions of Figure 5 and Table 5. 5.3 General description 5.3.1 The machining allowance and tolerance of the crank part are determined according to the Unit. mm 5.3.2 The machining allowance and tolerance of the cylindrical part (shaft collar, shaft tail and flange) are determined according to the maximum diameter D and the total length of the part L1.α is increased by 20% according to 4-step shaft forgings. 5.3.3 Whether the step and L gear forged or not is determined according to 4.4.6 Forgings without Machining6.1 Forgings without machining are the ones with all or part of the surface not machined. 6.2 The limit deviation of forgings without machining is as follows. the deviation of cross- section diameter or height shall be in accordance with the provisions of Table 6; the deviation of inner hole diameter or L gear shall be in accordance with the provisions of Table 7; and the deviation of length shall be in accordance with the provisions of Table 8. ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. 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