ASTM B478-85(1997)e1

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
e1
Designation: B 478 – 85 (Reapproved 1997)
Standard Test Method for
Cross Curvature of Thermostat Metals
This standard is issued under the fixed designation B 478; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Keywords were added editorially in May 1997.
1. 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.
FIG. 1 Specimen Relationships
1.2 The values stated in inch-pound units are to be regarded
as the standard. The metric equivalents of the inch-pound units
magnitude and direction of cross curvature (an inherent prop-
may be approximate. erty in thermostat metal).
1.3 This standard does not purport to address all of the
5. Apparatus
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 5.1 Fixture—A typical cross curvature fixture is shown in
priate safety and health practices and determine the applica- Fig. 2. It consists of a base which has a flat ground surface on
bility of regulatory limitations prior to use. its top side. For convenience a granite surface plate, as is
pictured, can be used. To it are attached side frames to support
2. Terminology
rod or bar tracks which are parallel to the top surface of the
2.1 thermostat metal—a composite material, usually in the base. On the tracks is assembled a movable carriage for
form of sheet or strip, comprising two or more materials of any mounting a micrometer depth gage.
appropriate nature, metallic or otherwise, which by virtue of 5.2 Micrometer Depth Gage, for measuring the position of
the differing expansivities of the components, tends to alter its the specimen to the nearest 0.0001 in. (0.0025 mm). The tip of
curvature when its temperature is changed. the gage rod shall be radiused.
2.2 cross curvature—the deviation from flat across the 5.3 Electronic Contact Indicator, sensitive, low-current, to
width, measured as a chord height. It is expressed in inches or give a signal when the micrometer depth-gage rod completes
millimetres.
the electrical circuit across the indicator terminals by touching
the specimen or the parallel.
3. Summary of Test Method
1 3
5.4 Parallel, hardened and ground steel, ⁄4 by ⁄8 by 6 in. (6
3.1 The test method for cross curvature consists of measur-
by 10 by 150 mm).
ing the chord height deviation from flat across the width of a
NOTE 4—Parallelism of the rods, on which the micrometer carriage
specimen of thermostat metal (Fig. 1).
traverses, to the steel parallel when laid on the surface plate shall be such
that when the carriage is traversed and micrometer readings are taken
NOTE 3—The highest point will normally be at or near the center of the
along the length of the parallel, no reading shall be different from any
specimen.
other reading by more than 0.0002 in. (0.005 mm).
4. Significance and Use
6. Sampling
4.1 This procedure provides the means for defining the
6.1 The method of sampling shall be mutually agreed upon
between the manufacturer and the purchaser.
This test method is under the jurisdiction of ASTM Committee B-2 on
Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee
7. Preparation of Sample for Measurement
B02.10 on Thermostat Metals.
7.1 The most important step in preparing the specimen for
Current edition approved Sept. 27, 1985. Published November 1985. Originally
published as B 478 – 68. Last previous edition B 478 – 68 (1972). measurement is cutting it to length. The length shall be
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
B 478
FIG. 2 A Typical Design of Apparatus
expansion side is convex, the results obtained shall be referred to as
approximately equal to the width. The minimum length of a
3 negative (−).
specimen shall be ⁄4 in. (20 mm). It must be cut in a manner
that will not tend to alter the inherent
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