Flat non-metallic washers come in a multitude of materials and sizes. Therefore, a review of certain definitions should be presented to make it easier for the buyer to order or an engineer to design a washer.
Concentricity and Position:
If you were to take the small circle and overlay it onto a large circle whereby each center was exactly on top of each other…you would have concentricity. The I.D. and O.D. circles created would be equidistant from one another as you moved around the washer. Nema tolerances permit a variance of .010 from center of washer. Both concentricity and position are considered location symbols dealing with tolerances.
A general rule of thumb when deciding if the wall of a washer can be created during the manufacturing process is…Subtract the I.D. from the O.D., then divide by two(2). If your answer is less than the thickness of the material you are using, there is a good chance the material will disintegrate in the die. Consult our office if you have any questions:
Material Thickness and Tolerances:
All materials that are manufactured have tolerances regarding thickness. All tolerances are not the same between materials. Check with our office before you enter the tolerances on the blueprint.
“Flash” and/or “Burrs”:
During the manufacturing process, fine “Hairlike” pieces of the material can form. This is called Flash. Burrs occur when there is a build up of the material along the exterior wall of the washer. This can be due to the composition of said material or clearance between bushing and punch. Sometimes tumbling may remedy the problem.
“Pitting” or “Breakout”:
On occasion the wall or edge of the washer may be void of material. This is usually the result of the material. During the manufacturing process, the resin or the substrate material (i.e. Canvas or Glass) may not adhere properly or you may come across hot and cold “spots” while the resin is setting. Most of the time this will not effect the performance of the materials. Consult our office if questions arise.
With the advent of QS-9000 and in certain cases, ISO-9001, key designation characteristics are appearing on blueprints. With “symbology”, KDC gives importance to dimensions by using terms like critical, major, minor, pollution and safety. For further information consult with our home office.