Washers are made from virtually any metallic or non-metallic material that can be stamped; including low and high carbon steels, steel alloys, copper, phosphor bronze, titanium, aluminum, fibre, mica, mylar, rubber, nylon, PTFE/polytetrafluoroethene, phenolic and many more. I.D. and O.D. can be configured to provide any size and shape required. They can be round, square, rectangular, hexagonal, oval, or non-symmetrical. They can also have tabs, crowns, notches, and may be countersunk in a variety of degrees.
In the manufacturing process, small stamping burrs are produced. A “normal” stamping burr is defined as 10% of stock thickness, but not less than .0005″. If this is acceptable, the drawing or specification should state “normal stamping burrs acceptable”. One method normally used to reduce stamping burrs is tumbling or vibratory deburring. While this will not completely eliminate burrs, the process smooths and reduces the protrusions. Costly “burr free” specifications on prints should be avoided, if possible.
If it is necessary that a part be finished by the application of a coating such as cadmium, zinc, nickel, anodize, silver or gold, the correct required finish should be clearly defined to avoid unnecessary expense. If commercial plating thickness is acceptable, it should be so noted. If a special thickness or a post finish is required, it should be clearly described and specified as such.
Wherever possible, specify commercial quality, low carbon steel. This generally meets most application needs in the most economical manner. Only specify tempered material if special hardness is critical to the application. Tempers such as 1/4 or 3/4 hard in steel are more difficult to obtain and, therefore, more costly.
Function & Cost
Commercially produced flat washers are designed to meet the needs of most applications relative to dimensional tolerances, hardness and surface conditions. Just about any special need can be met, but it should be remembered that the closer the tolerance, the greater the cost. Wherever possible, avoid specifying close tolerances or variations not warranted by the application.
Wherever possible, accept the surface condition of the material from which the washer is stamped. To meet a specification for a smoother surface finish may require such costly secondary operations as grinding or lapping.
Hardness Tolerance Range
As a general cost saving rule, keep tolerances as broad as possible. Specify, for example, a Rockwell “C” 45-50 rather that a Rockwell “C” 47-48 wherever it is acceptable. Case hardening tolerances should not be deeper that necessary (0.003″ to 0.005″ deep file hard is considered adequate for most applications).
There is an inverse relationship between quantity and price: the larger the production quantity, the lower the unit price. For economy, order the largest quantity possible. WCL may then schedule economical shipments of your parts in increments based on your anticipated needs and usage, rather than making a single delivery.