ASME B18.21.3:2008 pdf download

ASME B18.21.3:2008 pdf download.Double Coil Helical Spring Lock Washers for Wood Structures
1 INTRODUCTORY NOTES
1.1 Scope This Standard covers the dimensional and physical properties and methods of testing for double coil helical spring lock washers for wood structures. NOTE: The word lock appearing in the name of the product in this Standard is a generic term historically associated with the product’s identification and is not intended to imply an indefinite permanency of fixity in attachments where the fasteners are used. 1.2 Comparison to ISO Standards No comparable ISO standards exist for this part. 1.3 Dimensions All dimensions in this Standard are in inches and apply to unplated or uncoated product. 1.4 Options Options, if required, shall be agreed upon by the pur- chaser and the manufacturer or distributor. 1.5 Terminology For definitions ofterminology not specifically defined in this Standard, refer to ASME B18.12.
2 GENERAL DATA
2.1 Application The double coil helical spring lock washers for wood structures covered in this Standard are intended to be used with a curved flat washer or the standard hardware practice of the user against the wood. While not essen- tial, it is a good practice to use a standard round washer between the double coil helical spring lock washer and the nut, then tighten the nut in accordance with the users’ standard practice, and back off the nut 1 ⁄ 4 (90 deg) turn. This is important to maintain an acceptable pres- sure on the hardware and the wood fibers which may shrink or swell during varying weather conditions.Although these washers were designed specifically for use on bolts in wooden assemblies (poles, crossarms, etc.), they can also be used for general applications where a heavy duty double coil washer is needed. 2.2 Dimensions The dimensions of standard and extended travel dou- ble coil helical spring lock washers for wood structures are specified in Tables 1 and 2 and are before coating. Selections should be made from standard or extended travel series in Tables 1 and 2, respectively, to suit design requirements. 2.3 Material and Hardness 2.3.1 Material Composition. Washers shall be made from material meeting the chemical composition requirements of the following standards: (a) up to and including 3 ⁄ 4 in. carbon steel — SAE J403 1055-1065 (UNS G10550-G10650) (b) 7 ⁄ 8 in. and above boron steel — SAE J411 10B55- 10B65 2.3.2 Hardness. All washer section hardness requirements are 38 HRC to 46 HRC, 372 HV to 458 HV. To prepare washers for checking the material hardness, cut washer approximately in half so only one coil is used. Cold (water) grind or file both sides sufficiently flatand parallel to ensure a correctreading. Ifapplicable, be sure to remove the decarburized and coated surface. During this operation, care shall be exercised to prevent the surface temperature from exceeding 250°F. Refer to ASTM E 140 for hardness conversion. 2.3.3 Decarburization. Carbon steel and boron steel shall meet the limits for decarburization shown in Table 3. The method for testing limits shall conform to SAE J419.2.4 Washer Section The corners at the inner and outer peripheries of the washers shall be slightly rounded. The section of the finished washer shall be slightly trapezoidal with thick- ness at the inner periphery greater than the thickness at the outer periphery by a minimum of 0.0005 in. to a maximum of 0.001 in. per 0.0156 in. of the section width. The minimum section thickness specified in the dimen- sional tables represents the nominal mean thickness, T, of the trapezoid.