Washers:

Pilzecker is a product developer at MISUMI Europa, one of the world’s leading providers of mechanical engineering components. “Washers only have one single task,” he explains. “They are designed to distribute the force of the screw connection equally on the support structure.” However, there is an important restriction on their use, says the developer. ISO washers for metal connections have a stipulated ratio between the bore and outer diameter and this is 1.8 to 2 times larger. A typical example of this are washers according to ISO 7089 that can regularly be found in mechanical engineering. In the nominal size M 3, the bore diameter amounts to 3.2 mm and the outer diameter is 7 mm. “If the support structure is made of soft or very thin metal, large diameter washers – such as those according to DIN 9022 – must be used,” he explains. The outer diameter of these washers amounts to about 3 to 5 times the bore diameter. The thickness of the washer doesn't change substantially either, which means it would only be possible to distribute forces evenly over the washer to a limited extent.

“Designers are, however, often faced with the problem of the standard washers either being too large, too small or too thin,” Pilzecker continues. The outer diameter of the large diameter washers, for example, is 30 mm for M6 screws. “If there is only 25 mm of space for the washer as a result of the construction, what can the designer do? Switch to an ISO washer? This would be quite a risk with a thin sheet that has an outer diameter of just 12 mm.”

According to Pilzecker, the solution to the problem is “Make-to-Order” (MTO), i.e. the production of an individually configured component after an order is received. “It is not a problem for us to produce washers for M6 screws with an exact outer diameter of 25 mm,” he assures. “Even if only five units are required, we will even deliver just one single washer if that is what you need – and we can do this within a few days.” The customer may also have a say as to what material and surface treatment is used, explains the product developer. This is exactly what MTO specialises in.