Bosch’s HA3JAW adapter is a 1/2″ keyless 3-jaw drill chuck with an SDS-Plus shank that can be used with compatible rotary hammers to extend their usefulness beyond masonry drilling and chiseling applications.
As you might know, rotary hammers with SDS-Plus chucks cannot be used with drill bits, bit holders, or screwdriver bits that don’t have SDS shanks.
Some rotary hammers have rotary-only modes and even reversible variable speed motors, and so they could potentially be used for non-masonry drilling and driving tasks if not for the SDS chuck limitation.
Not that you would want to use a rotary hammer to replace your drill/driver in all applications, but this drill chuck adapter gives you the option to equip SDS-Plus rotary hammers with a much wider variety of drill and screwdriver bits.
User reviews indicate that the keyless chuck has a built-in locking mechanism that helps prevents bits from slipping or loosening in the jaws.
This and other drill chucks should only be used in rotary hammers that have rotary-only modes.
Alternatively, there are various SDS-Plus threaded adapters to which your choice of 1/2″ chuck can be attached. For instance, the Dewalt’s DW5351 SDS-Plus to 1/2″ chuck adapter ($13 via Amazon) can be used with their DW5353 1/2″ keyed chuck ($30 via Amazon) to create a complete accessory. Different shank adapters are available so that the same chuck could be used with different tool interfaces, such as spline.