ASTM D374 PDF

Historical Version s - view previous versions of standard. More D Determination of certain properties, such as relative permittivity dielectric constant and volume resistivity, usually require a knowledge of the thickness. Design and construction of electrical machinery require that the thickness of insulation be known.

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ASTM D Scope 1. Use these test methods except as otherwise required by a material speci? It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Referenced Documents 2.

Terminology 3. Summary of Test Methods 4. Current edition approved March 10, Published June Originally approved in Last previous edition approved in as D — A number in parentheses indicates the year of last reapproval. A superscript epsilon e indicates an editorial change since the last revision or reapproval.

This standard has been approved for use by agencies of the Department of Defense. The test methods identi? Table 1 and Table 2 display basic differences of each test method and identify test methods applicable for use on various categories of materials. Determination of certain properties, such as relative permittivity dielectric constant and volume resistivity, usually require a knowledge of the thickness.

Design and construction of electrical machinery require that the thickness of insulation be known. Apparatus 6. By use of a proper manipulative procedure and a calibrated spring see Annex A1 , the pressure exerted on the specimen is controllable. If necessary, equip the dial with a revolution counter that displays the number of complete revolutions of the large hand.

The limit is related to the compressive characteristics of the material being measured. The force applied to the presser foot spindle and the weight necessary to just prevent movement of the pointer from a higher to a lower reading shall be more than the minimum permissible force speci? An electronic instrument having a digital readout in place of the dial indicator is permitted if that instrument meets the other requirements of 6. The force applied to the presser foot spindle and the weight necessary to just prevent movement of the pointer from a higher to a lower reading must be more than the minimum permissible force speci?

Prior to calibration or thickness measurements, clean such surfaces by inserting a piece of smooth, clean bond paper between the anvil and the presser foot and slowly moving the bond paper between the surfaces. During measurements, check the zero setting frequently.

Failure to repeat the zero setting may be evidence of dirt on the surfaces. NOTE 1—Avoid pulling any edge of the bond paper between the surfaces to reduce the probability of depositing any lint particles on the surfaces. D — 99 stock or music-wire of known diameter are suitable substitutes. The wire or the plug gage has a diameter dimension that is known to be within Mount the ball in a fork-shaped holder to allow the ball to be conveniently moved from one location to another between the presser foot and the anvil.

The balls used commercially in ball bearings are almost perfect spheres having diameters constant within a few microinches. NOTE 2—Exercise care with this procedure.

Calculations using the equations in X1. Surfaces shall be? The shape, location, and number of these bands indicate the deviation from? Their number is a measure of deviation from? The number of fringes cut by a straight line connecting the terminals of any fringes is a measure of the deviation from? The condition of zero reading is satis? If this is not achievable after disassembly, cleaning, and lubrication, replace the instrument. Use standard gage blocks at points greater than 10 mil.

Calculate the arithmetic mean of these ten readings. Use standard gage blocks or other metallic objects of known thickness. Perform calibration procedures only after the instrument has been checked and found to meet the requirements of the pertinent preceding paragraphs of this standard. Perform calibration procedures at least once every 30 days. Reverse the rotation so as to open the micrometer 4 to 5 mils. Contact is made when frictional resistance initially develops to the movement of the calibrating device between the anvil and the spindle face.

Test Specimens 8. There may be instances, particularly when measuring very narrow strip specimens used for tensile tests, and so forth, when this requirement cannot be satis? In such cases, it is permissible to ignore this requirement. Procedures NOTE 3—In the remainder of this section the word test method denotes a combination of both a speci?

Each material will differ in its response to test method parameters, which include, but may not be limited to: compressibility, rate of loading, ultimate load, dwell time, and the dimensions of the presser foot and anvil.

For a speci? The procedures that follow are categorized according to the materials to which each applies. See also Appendix X1. In addition, use an instrument for either Test Method C or D that has: 9. Warning—Cleaning the presser foot and anvil surfaces as described in 7. To avoid these costs, obtain procedures for cleaning such electronic gages from the instrument manufacturer.

NOTE 4—An electronic gage may be substituted for the dial gage in Test Method C if the presser foot and anvil meet the requirements of that test method.

To help prevent this interference, select only clean specimens for testing and keep them and the thickness measuring instrument covered until ready to make measurements. Observe this initial reading and then open the micrometer approximately 4 mils beyond the initial reading and move the specimen to the? Avoid using measurement positions that are closer than mils from any specimen edge.

Observe the indicated thickness. The arithmetic mean of all thickness values is the thickness of the specimen. Adjust the zero point. See also Note 6. After correcting the observed indicated thickness using the calibration chart obtained in accordance with 7. A change in the setting is usually the result of contaminating particles carried from the specimen to the contacting surfaces of the presser foot and anvil. This condition necessitates the cleaning of these surfaces see 7.

Equilibrium is attained when the zero point adjustment becomes negligible. Do not stop the motor until all of the measurements are made.

This will minimize any tendency to disturb the thermal equilibrium between the instrument and the ambient during the thickness measurements. Avoid using measurement positions that are less than mils from any specimen edge. Test Method E is also the preferred test method for use with any paper of nominal thickness from 2 to 26 mils using a specimen consisting of a single sheet.

Test Method E does not prohibit the testing of single sheet specimens of paper having nominal thickness under 2 mils.

The micrometer reading of the stack, corrected from the calibration chart, is divided by the number of layers in the stack and reported as the thickness. Thickness of paper measured with a stack specimen deviates signi? NOTE 5—Originally, the selection of stack versus single sheet specimens was based on data obtained using manually operated micrometers. Those micrometers were perceived to have greater measurement reliability at the wider micrometer openings.

For very thin papers and values of n between 1 and 5, the ratio of total thickness of a stack of n sheets to n continuously decreases. Variations in thickness within a single layer are largely hidden in a stacked specimen which results in reduced ranges of high and low thickness observations on stack specimens versus single sheet specimens.

Avoid using measurement positions which are closer than mils from any specimen edge. Select these subsequent measurement positions so that they are approximately on a line parallel to the cross machine direction of the paper. If practicable, make ten readings. Avoid using measurement locations that are closer than mils from any specimen edge. Slowly lower the presser foot onto the initial measurement location and observe the initial reading between 2 and 4 s after the presser foot contacts the specimen surface.

Lower the presser foot to a dial reading approximately 0. NOTE 6—The procedure of 9. NOTE 7—When measuring the thickness of noticeably compressible electrical insulating papers, the purchaser and the supplier may wish to?

Observe this initial reading and then open the micrometer approximately 4 mils beyond the initial reading. This pressure is the result of the ratio of the force on the specimen exerted by gravity on the 3 oz weight of the presser foot assembly, out of contact with the lifting mechanism to the speci? One procedure uses the dial micrometer as a comparison gage. The other procedure uses the dial micrometer as a direct thickness reading instrument.

Test results using either procedure are not signi? The use of this technique does not require the construction of a calibration curve. Details of the comparison procedure follow. Make an initial reading 5 s after the presser foot has contacted the specimen surface. The initial reading estimates the specimen thickness.

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