A friction hinge holds its position at any point in its range of motion., allowing it to be positioned and left in place with minimal wiggle room. A classic example can be seen on laptop cases. The case stays shut until the user opens it, and will remain in the position the users leaves it in. Numerous computer applications call for friction hinges to position monitors and other devices. They can be used in other settings as well.
These devices are also called constant torque hinges. Several designs are available, using different technology to maintain the position of the hinge, with a variety of fasteners to attach to equipment like doors, computer cases, and mounting racks. A similar design has what is known as a detent stop, where the hinge will stop at a certain point and resume movement when pushed. This is not the same as a friction hinge, and may be used in different settings.
Each hinge is carefully tested during the manufacturing process. Designs need to move smoothly and seamlessly so operators do not need to jerk or pull at the hinge to get it to open. They also need to be able to bear large loads. Each friction hinge should have a weight rating, indicating how it can be used. Typically the rating on a hinge should exceed the application, to ensure it will continue to function even in adverse conditions.
In addition to having limited freeplay, friction hinges also don’t spring back. The minimal wobbling can be important for applications where the hinge needs to fix firmly in place. Prevention of springback also makes it hard to slap or slap something shut, which reduces the risk of damage. A laptop screen, for example, must be gently pushed into a closed position. This makes it less likely that a hasty or angry operator will damage the device, because the hinge limits the closing, and opening, speed.
Replacement friction hinge components are available through hardware and electronics supply stores. Hinges may be embedded inside an object’s casing, which may require some work to take it apart for the purpose of friction hinge servicing and maintenance. Before installation, it is advisable to check hinges over for signs of defects, and to oil them once in place so they will work smoothly. Oil can also prevent rusting of metal components, which can shorten a hinge’s lifetime and cause squeaking.