JB/T 7977-1999 This standard is a revision of JB/T 7977-95 "Cast Iron Ruler". During the revision, editorial changes were made according to relevant regulations, and the technical content remained unchanged. This standard specifies the type and size, technical requirements, inspection methods, marking and packaging of cast iron rulers with accuracy levels of "00", "0", "1" and "2". This standard is applicable to cast iron rulers with a working surface of 400 to 6300 mm. This standard was first issued in 1977 as JB 2214-77, revised to GB 6318-86 in April 1986, and adjusted to JB/T 7977-95 in April 1996. JB/T 7977-1999 Cast Iron Ruler JB/T7977-1999 Standard download decompression password: www.bzxz.net

ICS25.060.20
Standard of the Machinery Industry of the People's Republic of China
JB/T7977-1999
Castiron Straight Edge
Published on May 20, 1999
National Bureau of Machinery Industry
Implemented on January 1, 2000
JB/T7977—1999
This standard is revised on the basis of JB/T7977--95 "Castiron Straight Edge". This standard is consistent with the technical content of JB/T7977—95, and has only been re-edited according to relevant regulations. This standard replaces JB7977-95 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 unit of this standard: Chengdu Tool Research Institute. The main drafters of this standard: Cui Wenxiang, Zhang Yunsheng, and Sun Shikai. This standard was first issued in 1977 as JB2214-77, revised to GB6318-86 in April 1986, and adjusted to JB/T7977-95 in April 1996.
Standard of the Machinery Industry of the People's Republic of China
Cast iron straightedge
Cast iron straightedge
Replaces JB/F7977-95
This standard specifies the type and size, technical requirements, inspection method marking and packaging of cast iron straightedges with accuracy grades of 00, 0, 1 and 2.
This standard applies to cast iron straightedges with a working surface length of 400~6300mm (hereinafter referred to as straightedges). 2
This standard adopts the following definitions.
2.1 Straightedge
A measuring instrument with a flat measuring surface used to measure the plane shape error of a workpiece. 3 Types and dimensions
3.1 The type of the square foot is shown in Figure 1 (the figure is for illustration only and does not represent the detailed structure). The public plane of the side rain is the upper working surface, and the middle is made up of the mother working surface, leaving L (length) and the positive working surface. The supporting foot and the supporting surface are measured by the bridge shape. 1E=2L/9 is the optimal supporting distance height, thereby determining the standard supporting position C (degree) H (height) when the level ruler is inspected. The public plane of the continental surface is B (width) C (width) The public plane of the measuring surface is the public plane of the measuring surface. The edges of the working surface should be blunted, and the angle of the steel level ruler should not be greater than 0.1C×45° or the radius of the four corners should not be greater than 0.1C, but the maximum should not exceed 2mm. Figure 1 Flat Ruler
Approved by the State Bureau of Machinery Industry on May 20, 1999, and implemented on January 1, 2000
JB/T 7977—1999
3.2 The type of the two supporting feet of the bridge-shaped flat ruler is shown in Figure 2 (the figure is only for illustration and does not show the detailed structure). One end supporting foot (front leather)
3.3 The basic dimensions of the flat ruler are specified in Table 1. Specifications
1600°
I-shaped and ear-shaped flat rulersbzxZ.net
Note: For the dimensions with "*", it is recommended to make them into I-shaped flat rulers. 4 Technical requirements
Figure 2 Supporting feet
≥100
≥150
≥150
The other supporting feet (manufacturing parts)
Bridge-shaped flat feet
≥180
≥180
≥400
≥600
4.1 The working surface and side surfaces of the flat feet shall not have defects such as sand holes, pores, cracks, slag inclusions, shrinkage, etc. that seriously affect the appearance and performance. 4.2 The casting surface of the flat feet shall be cleaned of molding sand, flat, and firmly painted; the machined surface shall not have defects such as scratches, scratches, rust, etc. that seriously affect the performance.
4.3 The flat feet shall be made of high-quality fine gray cast iron or alloy cast iron, and the hardness of the working surface and side surfaces shall be 170~220HB. 2
JB/T7977-1999
The surface of the flat ruler should be scraped. For the side of the level 1 and level 2 flat ruler that is machined, the maximum allowable value of the surface roughness R is 2.5μm.
4.5 The straightness tolerance of the flat ruler surface and the straightness tolerance of any 200mm are specified in Table 2. Table 2
Any 200
! The values ​​in the table are given at a standard temperature of 20℃. 2 Calculation formula:
00 level: 0.6×(1+
0 level:
1x(1 +
Where: L-square foot.1. Length of work surface, mm. Precision
Straightness tolerance valueum
Grade 1: 2×(1+
Grade 2.4xt±-
3The straightness tolerance within 0.01L (maximum 10mm) from the edge of the work surface is not counted, and any point shall not be higher than the work surface. 20
Square foot The work surface should be color-coated and ground by scraping process. The ratio of the contact point area shown after grinding is shown in Table 3. Provisions: 46
or the number of contact points in a 25mm×25mm square area is as specified in Table 3, and the difference in the number of contact points in any 25mm×25mm area should 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. 4.7 The parallelism tolerance of the upper working surface and the lower working surface of the I and II-shaped straight ruler, the parallelism tolerance of the working surface of the bridge-shaped straight ruler and the supporting surface of the support foot, and the perpendicularity tolerance of the side of the straight ruler to the T-surface are as specified in Table 4. 3
JB/T 7977—1999
Ratio of contact point area within a unit area of ​​25mm×50mmNumber of contact points within an area of ​​25mm×25mm
≥16%
Note: The ratio of contact point area or the number of contact points within 0.01Z (generally 10mm) from the edge of the working surface is not counted, and any point shall not be higher than 1 working surface.
Parallelism tolerance of upper working surface and lower working surface (or supporting surface), etc.
Vertical tolerance of side surface to working surface||tt| |Note: The parallelism tolerance is 1.5 times the linear seat tolerance in Table 2: The trueness tolerance is 5 times the straightness tolerance in Table 2. 4.8
When the support point of I and II-shaped rulers is moved from the standard support position to the maximum support distance position, the natural deflection of the ruler is as specified in Table 5. 4.9 The ruler should be demagnetized and stabilized. 4.10 The side of I and II-shaped rulers should be marked with the standard support position; the end of the ruler should have a hanging or lifting device, and the device should be as far away from the standard support position as possible.
Note: The natural deflection of the ruler should not exceed 10μm/m. Inspection method
Straightness of working surface
JB/T7977—1999
Natural deflection
Use equal height blocks to support the 1.Ⅱ-shaped ruler at the standard support mark 2L/9 away from both ends of the ruler. Select an appropriate bridge plate according to the length of the ruler's working surface (generally 8 to 10 steps, with a span of 50 to 500mm). Then place the bridge plate at one end of the ruler and put a reflector or level. Fixed on the bridge plate; the bridge plate is gradually moved from one end of the ruler to the other end according to the span. Each time a span is moved, the position reading is read from the autocollimator with a graduation value of 1\ (or 0.005mm/m) or the electronic level with a graduation value of 0.001mm/m (the first-level ruler with a working surface length greater than 500mm can use the image level with a graduation value of 0.01mm/m, and the second-level ruler can use the frame level with a graduation value of 0.02mm/m); the difference between the maximum and minimum values ​​is the straightness error of the ruler working surface. The straightness error of any 200mm of the working surface can be determined by selecting a 50mm or 100mm bridge plate and inspecting it within any 200mm according to the above method. For rulers with a working surface width greater than 60mm, they should be inspected according to the flatness requirements, and their flatness tolerance value should not be greater than the straightness tolerance value specified in Table 2. The inspection method is shown in Figure 3. 13
5.2 Contact point area ratio
Apply a display agent to the working surface of the inspected ruler, grind it on a flat plate or ruler with a precision not less than that of the plate, and obvious contact points will be displayed on the working surface of the inspected ruler. Then use a transparent thin JB/T7977-1999
plate (such as a plexiglass plate) with 200 small squares of 2.5mm×2.5mm engraved within the range of 50mmx25mm, and place it at any position on the working surface of the inspected ruler, and observe the ratio of the area occupied by the contact points in each square in turn (in units of 1/10). Calculate the sum of the above ratios and divide it by 2 to get the ratio of the contact point area of ​​the inspected part. 5.3. Verticality of the side facing the working surface
Place the ruler on the flat plate, and make the dial with a scale of 0.001mm pass through the standard circle and zero on the standard square. Then, in the same way, make the dial base close to one side of the ruler. At this time, the reading of the dial gauge is the verticality error of the side. Similarly, check the verticality error of the other side and take the maximum error value (see Figure 4). Ruler
Standard Garden God
5.4 Parallelism between the upper working surface and the lower working surface, and the parallelism between the working surface and the lower supporting surface. Micrometer
Put the ruler on the precision flat plate with the working surface (or the supporting surface of the supporting foot) as the base surface, and use the micrometer with a scale of 0.001mm installed on the table frame to measure the height difference of no less than three places on its working surface, which is the parallelism error. When a suitable flat plate is not available, it is permitted to place the side of the straightedge on a supporting surface and use a lever with a graduation value of 0.002mm or a micrometer with a graduation value of 0.002mm to measure the height difference of the straightedge. 5.5 Natural deflection
Support the ruler with equal height blocks at the standard support marks 2L/9 away from both ends of the ruler and place it on the reference plane. Use an indicator or comparator with a graduation value of 0.001mm to measure the reading in the middle of the working surface length; then move the equal height blocks to the maximum support distance position (both ends of the ruler) and read the reading with the indicator or comparator after stabilization for 10 minutes: the difference Y between the two readings is the natural deflection of the ruler (see Figure 5). Micrometer or comparator
Reference plane
Marking and packaging
6.1 The ruler 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) Standard number of this standard.
6.2 The packaging box of the flat ruler should be marked with:
a) manufacturer's name or registered trademark;
b) product name:
c) specification and accuracy level:
d) product serial number and manufacturing date:
e) vibration-proof, waterproof, moisture-proof and other marks.
JB/T 7977—1999
6.3 The flat ruler should be treated with anti-rust treatment before packaging and should be well packaged. The product should not be damaged during transportation due to uneven packaging. 6.4 After the flat ruler 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 and product serial number of this standard.
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