The key is not in itself present in a shrink disk or clamping set, as these types of shaft-hub connection function quasi as an alternative to the keyway. Instead of positive power transmission, clamping sets or shrink discs are used, which do not require a keyway or similar.
It offers the advantage of having no wear or breaking points. The concentricity is also much higher, as everything is "form-fit". In other words, the shrink disc is shrunk onto the shaft and fits 100%, whereas with a keyway there is always a little play, which can lead to stress and abrasion during starting and braking. Therefore, a shrink disc or tensioner set will last longer and work more accurately, but are usually a little more expensive.