ASME B18.21.1-2009 pdf – Washers: Helical Spring-Lock,Tooth Lock, and Plain Washers (Inch Series).
3.1 Application: Tooth-Lock Washers
The tooth-lock washers covered in this Standard are intended for general application. The tooth-lock washers serve to increase the friction between the screw and the assembly. Internal tooth-lock washers are preferred where it is desirable to provide a smooth periphery.
3.2 Tooth Design: Tooth-Lock Washers
The selection of Type A or Type B tooth designs as shown in Fig. 3 and in Tables 6 through 10 shall be at the manufacturer’s option unless a specific design is designated by the purchaser.
The number of teeth, the length of the teeth, the width of the rim, and the thickness of the washer over the teeth (free height) shall be optional with the manufacturer. The projection of the teeth on both sides of the washer shall be relatively uniform.
3.3 Styles and Dimensions: Tooth-Lock Washers
Dimensions for the various types of washers are as follows; internal tooth-lock washers (Table 6), heavy internal tooth-lock washers (Table 7), external tooth-lock washers (Table 8), external tooth countersunk washers (Table 9), and internal/external tooth lock washers (Table 10).
3.4 Material and Hardness: Tooth-Lock Washers
3.4.1 Material Composition: Tooth-Lock Washers.
Washers shall be made from material meeting the chemical composition requirements of one of the following standards:
(a) Carbon Steel. SAE J403 1050—1065 (UNS G10500— G10650).
(b) Stainless Steel. SAE J405 301—305 (UNS S30100— S30500) or SAE J405 316 (UNS S31600).
(c) Stainless Steel. SAE J405 410 (UNS S41000).
(d) Copper Alloy. ASTM B 591 Type 425 (UNS C42500).
Other materials and grades shall be as agreed upon by the supplier and purchaser.
3.4.2 Hardness: Tooth-Lock Washers. Washers that are manufactured from carbon steel that show evidence of decarburization, or parts that were plated, shall have these surface layers removed before checking. During this operation, care shall be exercised to prevent the surface temperature of the washer from exceeding 250°F. It is recommended that the lighter, more sensitive depth reading HRA scale be used in lieu of HRC when testing washers of a thin section. Hardness requirements applicable to washers of the respective materials shall be as follows. Refer to ASTM E 140 for hardness conversions:
(a) Carbon Steel. 40 HRC to 50 HRC, 392 HV to 513 HV.
(b) Stainless Steel 301—305. Annealed 88 minimum HRB, hard through full hard 20 HRC to 45 HRC.
(c) Stainless Steel 410. 40 HRC to 50 HRC, 392 HV to 513 HV.
(ci) Copper Alloij. Temper H06 minimum.
3.5 Designation: Tooth-Lock Washers
Nominal washer sizes are intended for use with comparable screw or nut sizes. Fasteners conforming to this Standard shall be designated by the following data, in the sequence shown or by use of the code system in
ASME B18.24:
(a) product style (see para.3.3)
(b) tooth type if purchaser has preference (see para.
(c) ASME document number (ASME B18.21.1)
(d) nominal size (number, fraction, or decimal equivalent)
(e) maximum washer outside diameter (internal/ external tooth washers only)
f) washer type
(g) material (alloy or UNS number if applicable)
(h) surface protective finish standard number and thickness, if applicable
(1) Internal Tooth-lock Washer, ASME B18.21.1, ‘/4 in., Type A, 304 Stainless Steel.
(2) External Tooth-Lock Washer, ASME B18.21.1, 0.562 in., Type B, Carbon Steel.
(3) Internal/External Tooth-Lock Washer, ASME 818.21.1, No. 12 (0.900 O.D.), Type A, Carbon Steel, Mechanical Zinc per ASTM B 695, Class 55.
3.6 Processing: Tooth-Lock Washers
3.6.1 Finishes: Tooth-Lock Washers. Unless otherwise specified by the purchaser, lock washers shall be supplied with a plain (as-processed) finish, not plated or coated. Where corrosion preventative treatment is required, washers shall be plated or coated as specified by the purchaser.
3.6.2 Embrittlement: Tooth-Lock Washers. Electroplatmg carbon and boron steel-lock washers is not recommended because of the possibility of hydrogen embrittlement failures. When the purchaser specifies electroplated lock-washers, they must be baked immediately after plating using times and temperatures suitable for relieving all potentially trapped hydrogen.