JB/T 7978-1999 This standard is a revision of JB/T 7978-95 "Steel and Rock Straight Scales". During the revision, editorial changes were made according to relevant regulations, and the technical content remained unchanged. This standard specifies the types and sizes, technical requirements, inspection methods, marking and packaging of steel and rock straight scales with accuracy levels of "00", "0", "1" and "2". This standard is applicable to steel and rock iron straight scales with working surfaces of 400 to 2500 mm. This standard was first issued in 1977 as JB 2214-77, revised to GB 6319-86 in April 1986, and adjusted to JB/T 7978-95 in April 1996. JB/T 7978-1999 Steel Ruler and Rock Ruler JB/T7978-1999 Standard Download Decompression Password: www.bzxz.net

ICS25.060.20
Machinery Industry Standard of the People's Republic of China
JB/T7978-1999
Steel and rock straight edges
Steel and granite straight edges1999-05-20 Issued
National Bureau of Machinery Industry
2000-01-01 Implementation
JB/T7978-1999bZxz.net
This standard is revised on the basis of JB/T7978-95 "Steel and rock straight edges". The technical content of this standard is consistent with that of JB/T7978-95, and it has only been re-edited according to relevant regulations. This standard replaces JB/T7978-95 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 and Du Jimin. This standard was first issued in 1977 as JB2214-77, revised to GB6319-86 in April 1986, and adjusted to JB/T7978-95 in 1996.
Mechanical Industry Standard of the People's Republic of China
Steel and granite straightedges
Steel and granite straightedgesJB/T7978-1999
Replaces JB/T7978-95
This standard specifies the type and size, technical requirements, inspection methods, marking and packaging of steel and granite straightedges with accuracy grades of 00, 0, 1 and 2.
This standard applies to steel and granite straightedges with a working face length of 400~2500mm (hereinafter referred to as straightedges). 2
This standard adopts the following definitions.
2.1 Flat Ruler
The measuring surface is a plane, and it is a measuring instrument used to measure the plane shape error of the workpiece. 3 Type and Size
The type of flat ruler is shown in Figure 1 (the figure is only for illustration and does not show the detailed structure) 3.1
Upper Ding Working Surface
F Working Surface
(Length)
Upper Working Surface
Lower Working Surface
L (Length)
I-Shaped
1E-2L/9 is the best support distance, which determines the standard support position when the flat ruler is inspected. e
B (width)
H (height)
2 The edges of the working surface should be blunted, the chamfer of the pin flat ruler should not be greater than 0.18×45° or the radius of the corner should not be greater than 0.1B, the chamfer of the rock flat ruler should not be greater than 2×45° or the radius of the corner should not be greater than 2mm.
Approved by the State Machinery Industry Bureau on May 20, 1999, Figure 1 Flat Ruler
Implemented on January 1, 2000
The basic dimensions of the flat ruler are specified in Table 1.
JB/T7978—1999
Rock ruler
Technical requirements
Grade 00 and grade 0
Grade 1 and grade 2
The working surface and side surfaces of steel rulers shall not have defects such as cracks, scratches, bumps, rust, etc. that seriously affect the appearance and performance; 4.1
The working surface and side surfaces of rock rulers shall not have defects such as cracks, dents, loose structure, wear marks, burns, abrasions, etc. that seriously affect the appearance and performance. 4.2 Steel rulers should be made of high-quality carbon steel, alloy steel and other materials, and the hardness of their working surfaces should not be less than 500HV (quenched) or 170~245HV (unquenched).
Rock rulers should be made of fine-grained, densely structured gabbro, diabase, granite (biotite should be less than 5%, elastic modulus should be greater than 1.2×10~kg/cm2, water absorption should be less than 0.25%) and other materials, and the hardness of the working surface should be greater than 70HS. 4.3 The maximum allowable value of the surface roughness R of the working surface of the steel ruler is 0.16um, and the side is 0.63μm. The maximum allowable value of the surface roughness R of the working surface of the rock ruler is 0.32um, and the side is 1.25μm. The straightness tolerance of the ruler working surface and the straightness tolerance of any 200mm are specified in Table 2. 4.4
Valueμm
Straightness tolerance
Any 200
1The values ​​in the table are given at the standard temperature of 20℃. 2 Calculation formula:
00 level: 0.6×(1+
0 level:
1×(1+
Where: L is the length of the working surface on the flat ruler, mm.
JB/T7978—1999
Table 2 (finished)
Straightness tolerance value um
Level 1: 2x(1+
Grade 2: 4×(1+
3The straightness tolerance within the range of 0.01L (maximum 10mm) from the edge of the working surface is not counted, and any point shall not be higher than the L working surface. 4.5 The parallelism tolerance of the upper working surface and the lower working surface and the verticality tolerance of the side to the working surface are specified in Table 3. Table 3
Parallelism tolerance of the upper working surface and the lower working surface 3.9
Vertical tolerance of the side to the working surface
Note, the parallelism tolerance value is 1.5 of the straightness tolerance value in Table 2. Borrow: The straightness tolerance value is 5 times the straightness tolerance value in Table 2. 100
JB/T7978 1999
When the support point is moved from the standard support position to the maximum support distance position, the natural deflection of the ruler is as specified in Table 4. 4.6
Note: The natural deflection of the ruler should not be greater than 10μm/m. The steel ruler should be demagnetized and internal stress should be eliminated.
Natural deflection
4.8 The side of the ruler 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.
Inspection method
5.1 Straightness of the working surface
Support the ruler with equal height blocks at the standard support marks 2L/9 away from both ends of the ruler. According to the length of the working surface T of the ruler Select an appropriate bridge plate (usually 8 to 10 steps, with a span of 50 to 500 mm): then place the bridge plate at one end of the ruler, and fix the reflector or level on the bridge plate: the bridge plate is gradually moved from one end of the ruler to the other end according to the span, and each time a span is moved, read the position reading from an autocollimator with a graduation value of 1 (or 0.005 mm/m) or an electronic level with a graduation value of 0.001 mm/m (a level 1 ruler with a working surface length greater than 500 mm can use a composite level with a graduation value of 0.01 mm/m, and a level 2 ruler can use a frame level with a graduation value of 0.02 mm/m): the difference between the maximum and minimum values ​​is the working value of the ruler Straightness error of the surface. For the straightness error of any 200mm of the working surface, a 50mm or 100mm bridge plate can be selected, and the above method can be used to check and determine it within any 200mm.
For a flat ruler with a working surface width greater than 60mm, it should be tested according to the flatness requirements, and its flatness tolerance value should not be greater than the straightness tolerance value specified in Table 2. The inspection method is shown in Figure 2. 14
5.2 Verticality of the side to the T-surface
JB/T7978-1999
Place the flat ruler on a flat plate so that the base equipped with a micrometer with a graduation value of 0.001mm is zeroed on the standard square ruler through a standard round rod. Then, in the same way, make the base close to one side of the flat ruler. At this time, the reading on the micrometer is the verticality error of the side. Similarly, check the verticality error of the other side and take the maximum error value (see Figure 3). Flat Ruler
5.3 Parallelism Standard Circle God of Upper and Lower Working Surfaces
Micrometer
Put the flat ruler on the precision flat plate with the working surface as the base surface, and use the micrometer with a graduation value of 0.001mm installed on the table frame to measure the height difference of at least two places on its working surface, which is the parallelism error. When there is no suitable flat plate, it is allowed to put the side of the flat ruler on a supporting surface, and use a lever micrometer with a graduation value of 0.002mm or a gauge with a micrometer with a graduation value of 0.002mm to measure the height difference of the flat ruler. 5.4 Natural deflection
Use equal height blocks to support the ruler at the standard support mark 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 from the indicator or comparator after stabilizing for 10 minutes: the difference Y between the two readings is the natural deflection of the ruler (see Figure 4). L2
Micrometer or comparator
Reference plane
Marking and packaging
6.1 The flat ruler should be marked with:
a) Manufacturer's name or registered trademark:
b) Product name:
c) Specifications and accuracy level;
d) Product serial number and manufacturing date
e) Standard number of this standard.
6.2 The packing box of the flat ruler should be marked with:
a) Manufacturer's name or registered trademark;
b) Product name;
c) Specifications and accuracy level:
d) Product serial number and manufacturing date:
e) Vibration-proof, waterproof, moisture-proof and other marks.
JB/T7978—1999
6.3 The steel flat ruler should be treated with rust prevention and properly packaged before packaging. The flat ruler shall not be damaged during transportation due to improper packaging. 6.4 After the steel straight edge 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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