This standard specifies the general requirements for the machining allowances and tolerances of steel free forgings on hammers and their use. This standard applies to free 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 free forgings that exceed the scope specified in this standard, the allowances and tolerances shall be determined by negotiation between the supplier and the buyer. GB/T 15826.1-1995 General requirements for machining allowances and tolerances of steel free forgings on hammers GB/T15826.1-1995 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Machining allowances and tolerancesfor steel open die forgings on hammerGeneral reguirement
1 Subject content and scope of application
GB/T 15826.1—1995
This standard specifies the general requirements for the machining allowances and tolerances for steel open die forgings on hammer (hereinafter referred to as allowances and tolerances) and their use.
This standard is applicable to open 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 forgings beyond the scope specified in this standard, the allowances and tolerances shall be determined by negotiation between the supplier and the buyer. 2 Reference Standards
GB8541 Forging Terminology
3 Terminology
3.1 The definitions of basic dimensions, tolerances, steps, shoulders, black forgings and forging drawings of forgings shall be in accordance with the provisions of GB8541. 3.2 Machining Allowance
In order to give parts a certain machining size and surface roughness, a layer of metal for machining is left on the forgings at the part that needs to be machined on the surface of the part, which is called machining allowance (see Figure 1). 3.3 Residual Block
In order to simplify the shape of forgings and the forging process, some metal larger than the machining allowance is added to certain places of the forgings. This added metal is called residual block (see Figure 1).
3.4 ​​Blue
If the length of the step on the forging is less than 0.5 times of its own diameter, and this diameter is greater than 1.5 times of the diameter of the two adjacent ends, this step is called blue (see Figure 1). 3.5 Concave ridge
When the diameter of a part of a forging (or the cross-sectional dimension of a non-circular forging) is smaller than the diameter of the two adjacent parts (or the cross-sectional dimension is smaller), the part is called a concave ridge (see Figure 1).
Approved by the State Administration of Technical Supervision on December 13, 1995 and implemented on August 1, 1996
4 General description
Machining allowance
GB/15826.1-1995
4.1 The machining allowance and tolerance specified in this standard are divided into two grades. Grade F is used for forgings of general precision;
E is used for forgings of higher precision.
Note: Grade E often requires special tools and increases forging processing costs, so it is used for larger batch production. Flange
4.2 Unless otherwise specified, the shape and position tolerances of free forgings shall not be greater than the tolerance values ​​specified in this standard. 4.3 The machining allowances and tolerances specified in this standard are applicable to forgings made from rolled products. When forging with steel ingots, the allowances and upper deviations (lower deviations for inner holes and stoppers) are allowed to be increased by 50% according to the values ​​in this standard. 4.4 The allowances specified in this standard do not include the allowances for rough machining of machining chucks, heat treatment chucks, materials for physical and chemical inspections, and final heat treatment (quenching and tempering, etc.). These allowances should be increased according to the requirements of the purchaser. 4.5 For shaft parts (including smooth shafts, stepped shafts and crankshafts), the length dimensions of forgings can be rounded to 0 and 5 mm according to the principle of 2 minus 3 in, 7 back out and 8 in.
4.6 Method of drawing forging drawings
The outer shape of the forging is represented by a thick solid line, and the wheel line of the part is represented by a double-dotted line. The basic dimensions and tolerances of the forgings are marked above the dimension lines, and the dimensions of the parts are marked in brackets below the dimension lines (see Figure 2). t
Additional Notes:
This standard is proposed by the Ministry of Machinery Industry of the People's Republic of China. The National Forging Standardization Technical Committee is responsible for this standard. 58016
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This standard was drafted by Shanghai Mechanical and Electrical Industry Administration and other units. 530
The main drafters of this standard are Dong Zhusheng, Pan Baimao, Lv Xiancheng, Zhang Bingji and Xie Huazhen. H
From the date of implementation of this series of standards, the original JB4249-86 "Mechanical Processing Residues and Tolerances of Hammer Steel Free Forgings" standard will be invalid. 226
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