In this video we take a closer look at the keyway connection. The keyway connection is one of the shaft-hub connections (driver connections). The keyway connection is used in gearboxes, for example, to connect gears to the gearbox shaft and to transmit torque. The hub is the component that is to be connected to the shaft in a rotationally fixed manner (e.g. gear, pulleys, clutch discs, flywheels, fan wheels or brake discs). The power is transmitted between the shaft and the hub via the key. It is inserted into an axial groove milled into the shaft and protrudes a few millimeters from the shaft. There is also an axial groove in the gear hub itself so that the gear can be pushed over the shaft and the key. The force can now be transferred from the shaft to the hub via the key in a form-fitting manner. Since the key connection is a detachable connection, the components can be easily assembled and disassembled. The axial displacement can also be desired for specific purposes (e.g. sliding clutch). This is then referred to as a sliding fit and the key is referred to as a sliding spring. However, the weakening of the cross-section of the shaft due to the grooves incorporated can be a disadvantage. In addition, the grooves in the hub and shaft cause notch effects that lead to increased stress peaks. In addition, unlike a pure press connection, the key connection must be secured in the axial direction if displacement is not desired, which increases the design effort for the use of a locking ring or a grooved nut. In addition, tolerances between the key, shaft and hub can result in a small amount of play. This can lead to the grooves becoming worn out over time if the load changes. It is then no longer possible for the hub to be driven precisely by the shaft. In addition, the microscopic relative movement between the shaft and hub leads to so-called fretting rust or friction rust over time. This also leads to material weakening over time. DIN 6892 distinguishes between a total of 3 methods for the design of key connections. Method A is the most complex and deals with the strength verification of the shaft, the key and the hub under real conditions using a realistic experiment or extensive numerical calculation methods such as the finite element method. The standard does not prescribe a specific procedure for calculation method A. Calculation method B is less complex and the procedure is standardized. Method B takes into account in particular the surface pressure between the key and the groove in the hub and the groove in the shaft. This procedure is based on the assumption that the main failure criterion for the key connection is the permissible surface pressure between the shaft groove and the key or between the key and the hub groove. However, with method B, the strength verification for the shaft must be carried out in accordance with the nominal stress concept. Method B also takes into account shock loads, changes in load direction, load peak frequencies, frictional engagement factors, inhomogeneous load distribution over the key length as well as support and hardness influencing factors. There is also calculation method C for the approximate design of key connections. This method is also based on the assumption that the surface pressure is the decisive failure criterion of the key connection. For the sake of simplicity, a constant surface pressure is assumed over the entire key length and key height. Calculation method C can only be used if the direction of the torque does not change. Even if the length of the key is more than 1.3 times the shaft diameter, method C must not be used, since the shaft, key and hub will then be deformed too much and the surface pressure will no longer be constant over the entire length of the key. 00:00 Shaft-hub connection 01:03 How does a key connection work 02:04 Advantages of key connections 02:47 Disadvantages of key connections 03:52 Firm fit of the key 04:59 Light fit of the key 05:40 Sliding fit of the key 06:35 Design considerations: Offset hub 08:12 Calculation methods A, B and C 10:25 Power transmission 11:47 Determining the pressing force from the torque 13:19 Determining the load-bearing height of the key (contact surface) 15:00 Determining the load-bearing length of the key (contact surface) 16:15 Calculating the surface pressure 17:34 Slotted nut 19:28 Example of calculating the required key 22:24 Using 2 keys (load factor)