JB/T 7974-1999 This standard is a revision of JB/T 7974-95 "Cast Iron Plate". During the revision, editorial modifications were made according to relevant regulations, and the technical content remained unchanged. This standard specifies the types and dimensions, technical requirements, inspection methods, marking and packaging of cast iron plates with accuracy levels of "000", "00", "0", "1", "2" and "3". This standard is applicable to cast iron plates with working surfaces of 1600mm×100mm～4000mm×2500mm (length×width). This standard was first issued in 1985 as GB 4986-85 and adjusted to JB/T 7974-95 in April 1966. JB/T 7974-1999 Cast Iron Plate JB/T7974-1999 Standard download decompression password: www.bzxz.net

ICS25.060.20
Standard of the Machinery Industry of the People's Republic of China
JB/T7974-1999
Cast iron plate
Castiron surface plate
Published on May 20, 1999
National Bureau of Machinery Industry
Implemented on January 1, 2000
JB/T7974-1999
This standard is revised on the basis of JB/T7974-95 "Cast iron plate". The technical content of this standard is consistent with that of JB/T7974-95, and it has only been re-edited according to relevant regulations. This standard replaces JB/T7974-95 from the date of implementation. This standard is proposed and managed by the National Technical Committee for Standardization of Measuring Tools and Instruments. The responsible drafting units of this standard are: Chengdu Tool Research Institute, Wafangdian Machine Tool Factory, Lianghe Inspection Factory, Shangzhi County, Heilongjiang Province. The main drafter of this standard is Lai Wenxiang.
This standard was first issued in 1985 as GB4986-85 and was adjusted to JB/T7974-95 in April 1996.1
Mechanical Industry Standard of the People's Republic of China
Cast iron surface plate
Cast iron surface plate
JB/T 7974-1999
Replaces JB/T7974--95
This standard specifies the type and size, technical requirements, inspection methods, marking and packaging of cast iron surface plates with accuracy grades of 000, 00, 0, 1, 2 and 3. This standard applies to cast iron surface plates (hereinafter referred to as plates) with working surfaces of 160mm×100mm-4000mm×2500mm (length×width).
Cited Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised. Parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T1184—1996 Specifications for shape and position tolerances without tolerances 3 Definitions
This standard adopts the following definitions.
3.1 Plate
A plane reference device used for workpiece inspection or marking, also known as a platform. 3.2 Main fulcrum
When the plate contacts the mounting base or special bracket during processing, verification and use, it is used as the main supporting part. The supporting force at this time is in a static state.
3.3 Auxiliary fulcrum
When the plate is in use, it is a fulcrum added to prevent overturning due to the offset of the load center of gravity or harmful deformation due to excessive load. The support reaction force on the auxiliary support point should be smaller than the support reaction force on the main support point. 4 Type and size
4.1 The type of the flat plate is shown in Figure 1. The figure is for illustration only and does not represent the detailed structure. 4.2 The distribution of the main support points of the ribbed plate is shown in Figure 2. The auxiliary support points shown in the figure are set to prevent the flat plate from tilting due to the shift of the center of gravity during use. The auxiliary support points that cause harmful deformation due to excessive load shall be designed by the designer, but the number shall be kept to a minimum. The auxiliary support surface and the main support surface should not be on the same plane to facilitate the adjustment of the support reaction force of the auxiliary support points. 4.3 The basic dimensions of the flat plate are specified in Table 1. Approved by the State Bureau of Machinery Industry on May 20, 1999 and implemented on January 1, 2000
Support surface
Auxiliary fulcrum
a (length)
(e,f0.2)a
JB/T7974—1999
(0.1~0.2)a
Marking position
Main fulcrum
a (length)
160×100
160×160||tt ||250 × 160 | | tt | | 250 × 250 | | tt | | 400 × 250 | | tt | 1250×1250
1600×1000
1600×1600
2500 × 1600
4000×2500
5Technical requirements
Basic dimensions
Allowable deviation
JB/T79741999
Main dimensions
Basic dimensions
Allowable deviation
(reference)
5.1 The working surface of the flat plate shall not have defects such as sand holes, pores, cracks, slag inclusions, shrinkage, scratches, bumps, rust spots, etc. that seriously affect the appearance and performance.
5.2 The casting surface of the flat plate should be cleaned of molding sand and flat, and the paint should be firmly applied. 5.3 On the working surface of the flat plate with an accuracy grade of 0 to 3, sand holes with a diameter of less than 15mm are allowed to be blocked with the same material, and its hardness should be less than the hardness of the surrounding materials. The number of sand holes blocked on the working surface should not exceed 4, and the distance between the sand holes should not be less than 80mm. 5.4 The flat plate shall be made of high-quality fine gray cast iron or alloy cast iron, and its working surface hardness shall be 170-220HB. 5.5 The working surface of the flat plate shall usually be scraped. For the working surface of the level 3 flat plate processed by scraping, the maximum allowable value of the surface roughness R is 5μm.
5.6 The flatness tolerance of the flat plate is as specified in Table 2. 5.7 The working surface of the flat plate shall be tested by coloring and grinding when the scraping process is adopted. The ratio of the contact point area displayed after grinding is as specified in Table 3: or the number of contact points in the square area of ​​25mm×25mm is as specified in Table 3, and the difference in the number of contact points in any 25mm×25mm shall not be greater than 5 points. In case of dispute, the ratio of the contact point area shall be used as the basis for evaluation. 5.8 For the working surface of the flat plate that is not convenient to be tested by coloring and grinding, its plane fluctuation shall be tested. The plane fluctuation of the working surface is as specified in Table 4.
160×100
250×160
250×250
400×250
400×400
630×630
800×800
1000×630
1000× 1000
1250x1250
1600×1000
1600×1600
2500×1600
4000×2500
Diagonal d
1The values ​​in the table are given at standard temperature 20C2Calculation formula:
000 level: 1x(1+
000 level:
000 level:
2×(1+
4×(1 +
1 level:
JB/T7974—1999
2:16x(1+
3 level:40×(1+
where:d-diagonal length of flat working surface, mm.a
flatness tolerance value
3The flatness tolerance within 0.02a (maximum 20mm) from the edge of the working surface is not counted, and any point shall not be higher than the working surface. Table 3
Test Item
Ratio of contact point area per unit area
Number of contact points in a 25mm25mm square area000
≥20%
Accuracy Level
≥16%
Note: The ratio of contact defect area or number of contact points within 0.02a (maximum 20mm) from the edge of the working surface is not counted, and any point shall not be higher than 1. Working surface. 5.9
Accuracy grade
Plane fluctuation of plate working surface
JB/T79741999
The perpendicularity tolerance of the plate side to the working surface and the perpendicularity tolerance of the two adjacent sides of the plate are both grade 12 specified in GB/T1184. The concentrated load area in the center of the flat working surface, the applied rated load and the allowable lifting value are specified in Table 5. Table 5
160×100
160×160
250×160
250x250
400×250
400×400
630×400
630×630
800×800
1000×630
1000×1000
1250x1250
1600×1000
1600 ×1600
2500×1600
4000x2500
Diagonal d
The plate should be demagnetized and stabilized.
The concentrated load area is the circle with center D
Rated load
Allowable deflection value
5.12On the two opposite sides of the plate, there should be threaded holes (or cylindrical holes) for installing handles or lifting rings, and the design of the device position should minimize the deformation caused by transportation.
5.13If threaded holes (or grooves) are set on the working surface of the plate, their position should not be higher than the working surface. 6 Inspection method
Ratio of contact point area
Apply a display agent on the working surface of the inspected flat plate, grind it on a flat plate with a precision level not lower than that of the inspected flat plate, and display obvious contact points on the inspected flat plate. Then, place a transparent thin plate (such as a plexiglass plate) with 400 small squares of 2.5mm×2.5mm in a range of 50mm×50mm on any position of the inspected flat plate working surface, and observe the proportion of the area occupied by the contact points in each square in turn (in units of JB/T7974-1999
1/10). Calculate the sum of the above proportions, and divide it by 4 to obtain the ratio of the contact point area of ​​the inspected part. In order to obtain a typical value, the ratio of the contact point area should be measured at another position, and the average of the two results should be calculated. 6.2 Plane fluctuation
Place the plane fluctuation meter on the working surface of the flat plate, and move the plane fluctuation meter along any straight line direction. The moving distance is half a month of the length of the diagonal of the flat plate, which should not be less than 200mm. The difference between the maximum and minimum values ​​on the indicator of the plane wave meter (division value is 0.001mm) is the plane wave amount of the working surface of the inspected flat plate. The plane wave meter is shown in Figure 3. Thin elastic sheet
on the scale
6.3 deflection
Place the detection device on the working surface of the inspected flat plate: when no load is applied, make the torsion spring comparator probe contact the working surface (to make the measurement accurate, a thin gauge block can be placed between the probe and the working surface) and record the reading. Then apply force according to the rated load specified in Table 5 and record the reading; the difference between the two readings is the deflection value of the working surface of the inspected flat plate under the rated load. The detection device is shown in Figure 4. 7 Marking and packaging
Method weight (carrier)
Comparison light instrument
7.1 The flat plate should be marked with:
a) Manufacturer's name or registered trademark;
b) Product name:
c) Specification and accuracy grade;
d) Product serial number and manufacturing date:bzxz.net
e) Standard number of this standard.
7.2 The flat plate packaging box should be marked with:
a) Manufacturer's name or registered trademark;
b) Product name:
c) Specification and accuracy grade;
d) Product serial number and manufacturing date;
e) Anti-vibration, waterproof, moisture-proof and other marks.
JB/T7974—1999
Practice code support bed
7.3 The flat plate should be treated with rust prevention and properly packed before packaging, and the product should not be damaged during transportation due to poor packaging. 7.4 After the flat plate is verified to meet the requirements of this standard, it should be accompanied by a product certificate: the product certificate should have the standard number of this standard and the product serial number.
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