The QD design provides for both conventional (outboard flange) and reverse (inboard flange) mounting configurations, the initial sheave and pulley mounting system had been developed to promote component assembly and replacement.
The key difference between the two is that the bushing of the QD design has a flange along the outer rim, while the bushing in the taper lock has straight sides on the OD and is meant to fit flat. Many people refer to both types as a "taper lock" because the tapered wedging action is used by both to lock and the shaft. The taper bushing, with its straight sides, uses a fixed screw to push the bushing into the unit bore (sheave, sprocket, etc.) being mounted. When installing those screws, be careful. The openings on the bushing which have threads are for removal only. Stay mindful also that the presence of a flange outside the bushing doesn't automatically mean it's a QD type. Split Taper bushing always has a flange, so neither can be interchanged. The QD style has a break, which continues on through the flange.
The Steel QD (Quick Disconnect) Style bushing offers compact and quick installation while providing outstanding retaining capacity. QD Bushings are used in the industry which provides simplicity and versatility in design. They are Steel-quality precision machined and are installed by tightening several cap screws. That draws the bushing into the product's taper bore which compresses the bushing's bore. QD bushings are quickly removed by jack-screws in the cap screws.
In QD Bushings, double drilled holes are fitted for mounting of the component in traditional or reverse positions. This allows for the installation of cap screws via product hub or bushing flanges whichever is most convenient. Installation has significant advantages; cap screws are always inserted from the outside where they are easily accessible.