GOST 8.426-81

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  ГОСТ 8.426-81

GOST 8.426−81 State system for ensuring unity of measurements (GSI). Instruments for measuring the hardness of metals by the method of elastic rebound of the striker (shore a). Methods and means of verification

GOST 8.426−81

Group Т88.1*
_________________________________________
* In the index «National standards» 2005
group Т88.2. — Note the CODE.

STATE STANDARD OF THE USSR

State system for ensuring the uniformity of measurements

INSTRUMENTS FOR MEASURING THE HARDNESS OF METALS BY THE METHOD OF ELASTIC REBOUND OF THE STRIKER (SHORE A)

Methods and means of verification

State system for ensuring the uniformity
of measurements. Shore rebound hardness testing
machines. Methods and means of verification

Date of introduction 1983−01−01

DEVELOPED by the State Committee of USSR on standards

PERFORMERS

O. M. Cochin, candidate. Fiz.-Mat. Sciences (head of subject); N.With.Husyatyn, PhD. tech. Sciences

MADE with the USSR State Committee for standards

Member Of The State Standard L. K. Isaev

APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards, dated 4 June 1981 N 2805

INSTEAD OF MU 224

This standard applies to devices for measuring the hardness of metals by the method of elastic rebound of the striker (shore a) hardness shore (further — hardness) produced according to GOST 24746−81, and establishes the methods and means of their initial and periodic verifications.

1. OPERATIONS AND MEANS OF VERIFICATION

1.1. During the verification needs to be performed the operation and applied means of verification specified in the table.

1.2. Allowed to use other means of verification that meets the accuracy requirements of this standard.

1.3. Diamond striker being checked after repair of a hardness tester according to claim.3.3.2−3.3.5 only if the firing pin has also been repaired.

1.4. Diamond hammer head according to claim.3.3.1−3.3.5 confide with the release of his production.

1.5. Diamond striker confide during operation in PP.3.3.2−3.3.5 if there are doubts about his health (after the impact of the alleged damage to the fastening of the diamond, etc.)

2. CONDITIONS OF VERIFICATION AND PREPARATION FOR IT

2.1. During the verification of hardness testers you must meet the following conditions:

the temperature of the air in the room 15−28 °C;

the relative humidity of the indoor air (65±15)%.

2.2. Check the hardness must be installed level built-in hardness, on the table, the design of which needs to be protected from the hardness of the impact vibrations transmitted through the walls and floor of the building.

2.3. The test head of the tester must be installed in the desktop device that is included in the hardness tester.

2.4. The surface of the table base, the workers and the supporting surface of the exemplary measures the hardness should be clean and degreased with alcohol according to GOST 131−67*.
_______________
* On the territory of the Russian Federation GOST R 52193−2003. — Note the CODE.

2.5. Before proving the diamond pin must be cleaned and degreased with alcohol according to GOST 131−67.

3. VERIFICATION

3.1. External examination of hardness

At external examination should be installed:

compliance with the completeness of the hardness of the requirements of GOST 24746−81;

the lack of hardness and adaptation to it of traces of corrosion and mechanical damage, as well as the uniformity of the color of the hardness (with no gaps, stains and peeling).

3.2. Interaction check moving parts of the hardness tester

3.2.1. The interaction of the moving parts of the hardness test when applied at least four prints on the standard measure of the hardness of the 2nd category of its type with a hardness value (95±7) HSD. When the last three blows the meter needle should move smoothly, without jerks and jamming and set the zero of the scale before the hammer starts to fall on the test surface.

3.3. Calibration of diamond striker

3.3.1. Visual inspection of the diamond striker

3.3.1.1. When viewed from the outside surfaces of frames and holders must have no holes, cracks, burrs, dents, scratches, traces of corrosion and other mechanical damage visible to the naked eye.

3.3.1.2. For a survey of the diamond and its lateral spherical surface of the firing pin is mounted so that its axis was a continuation of the optical axis of the microscope. Bring a microscope so that he could clearly see the entire surface of the pad, and then changing the focus, examine the spherical surface.

On the surface of the working part of the diamond boyka at a height of not less than 0.3 mm from the surface of the ground should be no cracks, scratches, chips, fractures and other defects.

3.3.2. Measurement of the geometric dimensions of the diamond striker

3.3.2.1. The diameter of the tool holder lever is measured with a micrometer at three cross-sections in two mutually perpendicular directions. Each value of the diameter should be 7,938mm.

3.3.2.2. The length of the striker is measured by Vernier caliper. The length of the striker should be (101,6±0,5) mm.

The diameter of the rim is measured with a micrometer. The value of the diameter of the rim must be 5mm. Overhang the rim of the holder is measured on the microscope. The value of departure of frames from the holder must be (9,25±0,05) mm.

3.3.3. The determination of the mass of diamond striker

The mass of the striker determine the diamond on laboratory scales with divisions of not more than 0.05 g. the Mass of diamond striker should be 36,0g

3.3.4. Measurement of the geometric dimensions of the working part of diamond striker

When measuring the geometric dimensions of the working parts of diamond of the striker determine the height of the working part of the diamond at its axis, diameter area and the radius of the sphere of diamond, the eccentricity of the diamond relative to the axis of the holder.

3.3.4.1. To measure the height of the working part of the diamond when the pin is mounted on the microscope stage so that its axis is perpendicular to the optical axis of the microscope. Microscope focus the reflected light on the contour of the axial cross-section of diamond and striker turn around the axis found on the border of the polished and unpolished parts of the diamond point closest to the site. Measure the distance along the axis of the diamond from the ground to the plane passing through this point. The height of the working part of the diamond should be at least 0.3 mm.

3.3.4.2. To measure the diameter of the diamond pin is mounted so that its axis was a continuation of the optical axis of the microscope. Microscope focusing on the surface area and measure its diameter in two mutually perpendicular directions. The difference between diameters must not exceed 0,03 mm. arithmetic mean diameter should be 0.3mm.

3.3.4.3. For the measurement of the sphere radius of the diamond pin set on the table of the projector so that its axis was perpendicular to the axis of the light beam of the illuminator. Shadow image of a radius of the sphere projecting on the projection screen. On the screen set the template that needs to be shown the contours of a sphere with a radius of from 0.85 to 1.15 mm every 0.05 mm in a zoom of the projector.

To determine the radius of the sphere of diamond consistently combine his shadow image with the contours of the radii on the template. The radius value specified in the circuit on the template that is most closely adjacent to the contour of the shadow image, taking the value of the sphere radius of the diamond in this plane.

In each of two mutually perpendicular planes is carried out at least three measurements. To determine the radius of the sphere in any plane calculate the arithmetic average of the three results. To determine the radius of the sphere of diamond calculate the arithmetic mean of the measurements in both planes.

The radius of the sphere of the diamond should be (1±0,1) mm. the difference between the radii measured in two mutually perpendicular planes, must not exceed 0.2 mm.

3.3.4.4. To measure the displacement of the site of the diamond of the firing pin relative to the axis of the firing pin holder is mounted so that its axis is perpendicular to the optical axis of the microscope. Focusing the microscope in transmitted light on the contour of the working part of the diamond at the transition site in the area. Rotating firing pin relative to the axis of the holder, find the rightmost position of the shadow contour of the diamond and combines with a transition point any dashed line ocular head. Removed the first reference. Rotating firing pin relative to the axis of the holder, find the leftmost position of the shadow contour of the diamond and the rotation of the micrometer screw lateral movement of the table combine the transition point previously selected with a dashed line ocular head. Remove the second reference. The measurements were carried out three times. The eccentricity of the working side of the striker relative to the holder taking the arithmetic average of three one-half of the difference 1 and 2 counts.

The displacement of the center of the site of the diamond of the firing pin relative to the axis of the holder must be no more than 0.1 mm.

3.3.5. Determination of surface roughness of the working part of diamond striker

The roughness of the working parts of diamond boyka determined by sampling 5% of the total number of dies produced, but not less than two.

3.3.5.1. To determine the roughness of the spherical surface of the diamond when the pin is mounted so that the optical axis of microinterferometer was perpendicular to the surface of a sphere. Focusing the microscope, you get an interference pattern having the form of a family of elongated parabolic curves. Rotating the hammer around the axis, visually determine the location with the maximum roughness parameter, which determine the roughness.

3.3.5.2. To determine the roughness of the surface of the ground diamond the firing pin mounted on microinterferometer so that the axis of the firing pin is kept on the optical axis of microinterferometer.

3.3.5.3. The roughness parameter of the spherical surface should be not more than 1.6 µm, the surface of diamond is not more than 0.2 µm according to GOST 2789−73.

3.3.6. The variance of the readings of sample shore hardness tester with test head from the testimony of exemplary hardness shore a model with brisk

The deviations determined by the comparison of the readings of sample hardness on the same plot of exemplary measures hardness 2nd category of its type when installed on the hardness of alternately exemplary and verified strikers. The hardness of the pre-focus with a model head and get stable readings.

3.3.6.1. Prints are exemplary and verified strikers when testing is applied in close proximity to each other, the distance between adjacent prints is not less than 2 mm.

3.3.6.2. The deviations determined in three exemplary measures hardness 2nd discharge type, its values of hardness (95±7) HSD, (60±7) HSD and (30±7) HSD. Each extent, fulfill the seven dimensions that account for the last five.

3.3.6.3. The deviation of the last five hardness values obtained in the measurement test of the striker, from the average value obtained in the measurement model of the striker within the selected work area is a good measure of hardness should not exceed ±1,5 HSD on each of the three measures.

3.4. Determining the absolute error of the hardness tester via hardness

When determining absolute error on each measure of hardness is performed first one or two test prints. Then perform at least five of the prints, placing them evenly over the surface of the steps, the counts removed with an accuracy of ±0,5 HSD. According to the results of individual measurements, find the arithmetic mean of the hardness value. Absolute error of hardness is defined as the difference between the found average hardness value and the hardness value indicated on a standard measure. The absolute error of the hardness tester when testing it on each of the three exemplary measures the hardness must not exceed the maximum permissible error specified in GOST 24746−81.

3.5. The definition of variation (scale) readings of hardness in hardness

To determine the variation of the hardness tester is applied to measure five prints in close proximity to each other, but not closer than 2 mm. the Variation of the readings of hardness is defined as the difference between the highest and lowest hardness values, obtained by five measurements.

The variance (scale) of the hardness tester when testing it in each of the three exemplary measures the hardness should be no more than specified in GOST 24746−81.

4. THE RESULTS OF THE VERIFICATION

4.1. The results of the initial verification of the manufacturer draws up a record in the passport.

4.2. The hardness, recognized fit with government verification, certificate of state verification in the form prescribed by the state standard. On the reverse side of the certificate identify the diamond firing pin, which was believed to hardness.

Verification results are entered into the calibration Protocol, the form of which is given in mandatory Appendix 2.

4.3. The results of periodic Agency verification issue in the manner prescribed by departmental metrological service.

4.4. Hardness of not satisfying the requirements of this standard, marriage. They give notice of unfitness.

ANNEX 1 (mandatory). TECHNICAL REQUIREMENTS FOR EXEMPLARY MEASURES THE HARDNESS OF ITS TYPE

ANNEX 1
Mandatory

1. Hardness should be made in the form of bars of square section with two intersecting surfaces or in the form of tiles round shape with one working surface.

Bar length measures of hardness — (80±1) mm, width and height (25±1) mm. the diameter of the tile (65±1) mm, height — (15±1) mm.

2. Working and support surface measures of hardness should be flat. Deviation from flatness shall be not more than 0.01 mm over the whole surface and not more than 0,003 mm at the surface area of 25x25 mm.

3. The deviation from parallelism of the working and bearing surfaces — not more than 0,015 mm.

4. The roughness parameter of the surfaces of the measures of hardness according to GOST 2789−73 should be, mcm, not more than:

0,32 — workers;

0,63 — for reference;

1,25 — side.

5. The nominal value of the hardness measures and the scope of these values shall be as specified in the table.

HSD

The difference between the results of the hardness measurements of the two working surfaces (the form of the action bar) must be no more than 0.5 HSD.

ANNEX 2 (mandatory). FORM of a PROTOCOL testing device for measuring the hardness of metals by the method of elastic rebound of the striker (shore a)

ANNEX 2
Mandatory

PROTOCOL
calibration of instrument for measuring the hardness of metals by the method of elastic rebound
boyka (shore a) type ________________, owned by

5. The results of determining the absolute error of the instrument for hardness:

6. The results of the determination of the variation (magnitude) indication of hardness of hardness: