ASTM_B_362_-_91_2016.pdf

Designation:B36291(Reapproved 2016)Standard Test Method forMechanical Torque Rate of Spiral Coils of Thermostat Metal1This standard is issued under the fixed designation B362;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 The test method covers the principles of determining themechanical torque rate of spiral coils of thermostat metal.NOTE1This test method has been developed particularly to cover thedetermination of the mechanical torque rate of spiral coils made ofthermostat metal for carburetors and manifold heat controls.The methodis not limited to thermostat metals and can be used for spiral coils of othermaterials for which the torque rate must be measured accurately.1.2 The values stated in inch-pound units are to be regardedas the standard.The metric equivalents of inch-pound unitsmay be approximate.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to become familiarwith all hazards including those identified in the appropriateSafety Data Sheet(SDS)for this product/material as providedby the manufacturer,to establish appropriate safety and healthpractices,and determine the applicability of regulatory limi-tations prior to use.2.Terminology2.1 thermostat metal,na composite material,usually inthe form of sheet or strip,comprising two or more materials ofany appropriate nature,metallic or otherwise,that,by virtue ofthe differing expansivities of the components,tends to alter itscurvature when its temperature is changed.2.2 mechanical torque rate,nthe ratio of torque to deflec-tion.It is a measure of the stiffness of the coil and may have theunits of ounce inch or gram centimetre per angular degree.2.3 spiral coil,na part made by winding strip on itself.3.Summary of Test Method3.1 The test for mechanical torque rate of spiral coilsconsists of applying a torque,or moment of force,that will notstress the material in excess of its elastic limits,to the coil andmeasuring the resulting deflection as angular rotation.Of theseveral methods for obtaining this value,it is preferred that theouter end of the spiral coil be held stationary,but not fixed,andthe inner end of the coil be rotated after applying a load to theouter end of the coil at a fixed radius.4.Significance and Use4.1 This test method is useful to determine the mechanicalforce of spiral coils of thermostat metal.4.2 The mechanical properties of a coil may vary from lot tolot of thermostat metal material.This method is useful fordetermining the optimum thickness and length of the materialfor a given mechanical torque specification.4.3 This test is useful as a quality test to determine accep-tance or rejection of a lot of thermostat metal coils.5.Apparatus5.1 The determination of the mechanical torque rate ofspiral coils is subject to many variables and is sensitive to thedegree that even different apparatus employing the same testprinciples will give different results.Therefore it is recom-mended that the apparatus be standardized.The apparatusshown in Fig.1 and Fig.2 and consisting essentially of thefollowing components,has been found satisfactory:5.1.1 Specimen HolderA specimen holder shall providefor securely holding the inner end of the test specimen.Preferably,the holder or mounting arbor shall be of circularcross section whose diameter is as large as possible withouttouching the inner turn of the coil under any test conditions ofload.The end of the arbor shall be slotted entirely across itsdiameter,to a depth greater than the width of the specimen,andof a width slightly narrower than the thickness of the specimen.Thus,the inner tab will be a push or snug fit in the slot for itsentire width.The edges of the slot shall be sharp where itintersects the circumference of the arbor.The slot shall be sopositioned in the arbor that the center of rotation of the arborand the coil will coincide.5.1.2 ProtractorThe angular deflection due to the testtorque shall be measured by a protractor with a minimumdivision of 0.5 angular degrees.5.1.3 Loading PinThe loading pin is the member bymeans of which the load is applied to the outer end of the coil.The pin shall be preferably of circular cross section approxi-mately332in.(2.4 mm)in diameter.The distance from the1This test method is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of SubcommitteeB02.10 on Thermostat Metals and Electrical Resistance Heating Materials.Current edition approved May 1,2016.Published May 2016.Originallyapproved in 1960.Last previous edition approved in 2008 as B362 91(2008).DOI:10.1520/B0362-91R16.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Cons