ASTM B478-85(2008)
(Test Method)Standard Test Method for Cross Curvature of Thermostat Metals
Standard Test Method for Cross Curvature of Thermostat Metals
SIGNIFICANCE AND USE
This procedure provides the means for defining the magnitude and direction of cross curvature (an inherent property in thermostat metal).
SCOPE
1.1 This test method covers the determination of cross curvature of thermostat metals.
Note 1—This test method is not limited to thermostat metals and can be used for other materials for which the cross curvature must be measured accurately.
Note 2—This standard includes means for calculating cross curvature for widths other than that of the specimen having the same radius of curvature.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to become familiar with all hazards including those identified in the appropriate Material Safety Data Sheet (MSDS) for this product/material as provided by the manufacturer, to establish appropriate safety and health practices, and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: B478 − 85(Reapproved 2008)
Standard Test Method for
Cross Curvature of Thermostat Metals
This standard is issued under the fixed designation B478; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
NOTE 3—The highest point will normally be at or near the center of the
1. Scope
specimen.
1.1 This test method covers the determination of cross
curvature of thermostat metals.
4. Significance and Use
NOTE 1—This test method is not limited to thermostat metals and can
4.1 This procedure provides the means for defining the
be used for other materials for which the cross curvature must be
magnitude and direction of cross curvature (an inherent prop-
measured accurately.
erty in thermostat metal).
NOTE 2—This standard includes means for calculating cross curvature
for widths other than that of the specimen having the same radius of
5. Apparatus
curvature.
1.2 The values stated in inch-pound units are to be regarded 5.1 Fixture—A typical cross curvature fixture is shown in
Fig. 2. It consists of a base which has a flat ground surface on
as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only its top side. For convenience a granite surface plate, as is
pictured, can be used. To it are attached side frames to support
and are not considered standard.
rod or bar tracks which are parallel to the top surface of the
1.3 This standard does not purport to address all of the
base. On the tracks is assembled a movable carriage for
safety concerns, if any, associated with its use. It is the
mounting a micrometer depth gage.
responsibility of the user of this standard to become familiar
with all hazards including those identified in the appropriate 5.2 Micrometer Depth Gage, for measuring the position of
Material Safety Data Sheet (MSDS) for this product/material
the specimen to the nearest 0.0001 in. (0.0025 mm).The tip of
as provided by the manufacturer, to establish appropriate the gage rod shall be radiused.
safety and health practices, and determine the applicability of
5.3 Electronic Contact Indicator, sensitive, low-current, to
regulatory limitations prior to use.
give a signal when the micrometer depth-gage rod completes
the electrical circuit across the indicator terminals by touching
2. Terminology
the specimen or the parallel.
2.1 thermostat metal, n—a composite material, usually in
1 3
5.4 Parallel, hardened and ground steel, ⁄4 by ⁄8 by 6 in. (6
the form of sheet or strip, comprising two or more materials of
by 10 by 150 mm).
any appropriate nature, metallic or otherwise, which by virtue
NOTE 4—Parallelism of the rods, on which the micrometer carriage
of the differing expansivities of the components, tends to alter
traverses, to the steel parallel when laid on the surface plate shall be such
its curvature when its temperature is changed.
that when the carriage is traversed and micrometer readings are taken
2.2 cross curvature, n—the deviation from flat across the
along the length of the parallel, no reading shall be different from any
width, measured as a chord height. It is expressed in inches or other reading by more than 0.0002 in. (0.005 mm).
millimetres.
6. Sampling
3. Summary of Test Method
6.1 The method of sampling shall be mutually agreed upon
between the manufacturer and the purchaser.
3.1 The test method for cross curvature consists of measur-
ing the chord height deviation from flat across the width of a
7. Preparation of Sample for Measurement
specimen of thermostat metal (Fig. 1).
7.1 The most important step in preparing the specimen for
measurement is cutting it to length. The length shall be
approximately equal to the width. The minimum length of a
This test method is under the jurisdiction of ASTM Committee B02 on
Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee
specimen shall be ⁄4 in. (20 mm). It must be cut in a manner
B02.10 on Thermostat Metals and Electrical Resistance Heating Materials.
that will not tend to alter the inherent cross curvature. It is
Current edition approved Nov. 1, 2008. Published November 2008. Originally
recommended that a shear with sharp blades and the proper
approved in 1968. Last previous edition approved in 2003 as B478–85(2003).
DOI: 10.1520/B0478-85R08. clearance be used. The shearing should impart no burrs to the
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