SUMMER 2012

THE DISTRIBUTOR’S LINK

THE DISTRIBUTOR’S LINK 161 HOW TO DESIGN THE OPTIMUM HINGE continued from page 46 The minimum thickness of the outer members should be 1 to 1 1/2 times the diameter of the pin. If the thickness of the outer members are less than the diameter of the pin, then the tight fit should be in the inside hole. To design a free fit hinge, first establish maximum hole size in the retaining component (tight fit). Insert the Coiled Pin into the retaining component and measure the free diameter of the pin at the center of the span. Add a factor to provide some clearance for the rotating member, usually .001” (0.02 mm) to establish the minimum diameter of the free hole. Then add the required production tolerance to assign the maximum diameter of the free hole. If the tight fit is on the inside member of the assembly, as the pin is installed there becomes a sized and an unsized end of the pin (Figure 2b). The end of the pin that has not been inserted through the hole is larger than the end that has been sized by the hole. Therefore, measure the diameter of the unsized end to determine the minimum diameter of the free hole in the outside members. Friction Fit Hinge In a friction fit hinge, all of the holes should be sized identically within the assigned tolerances. If the manufacturer is unable to maintain the same hole size within each component, the tolerance should be split between the components. It is most common to assign the smaller half of the tolerance to the outside holes and larger half to the inside hole.The Coiled Pin simplifies design as there is no need to incorporate misalignment between holes to achieve friction, as is the case with rigid Solid Pins. Coiled Pins perform best when installed in straight, properly aligned holes. The Coiled Pin’s spring characteristics can be used to achieve exceptional performance and maintain desired fit and function throughout the life of the product. Although this article offers general design guidelines, it is recommended that Application Engineers who specialize in fastening and joining be consulted to ensure the optimum hinge design is employed for each application.