open grooves interacting with the driving wedges and two closed grooves held by locking balls. This is the most common size and takes a hammer up to 4 kg. The wedges grip an area of and the shank is inserted 40 mm into the chuck. SDS-top A 14 mm shank similar to SDS-plus, designed for hammers from 2 to 5 kg. The grip area is increased to and the shank is inserted 70 mm. This size remained uncommon and was discontinued in 2009. SDS-max An 18 mm shank with three open grooves and locking segments rather than balls. It is designed for hammers over 5 kg. The wedges grip an area of and the shank is inserted 90 mm. Many SDS drills have a "rotation off" setting, which allows the drill to be used for chiselling. The name SDS comes from the German Steck-Dreh-Sitz (insert-drill-attachment). In German-speaking countries the acronym Spannen durch System (Clamping System) was also used, though Bosch now uses Special Direct System internationally. Chucks with both indexable positioning and indexable clamping Commercial production machining now makes use of increasingly advanced chucks which have not only indexable positioning but also indexable clamping. Both functions are typically hydraulically controlled. The clamping is often done with each pair of jaws consisting of one fixed jaw and one movable jaw (hydraulically actuated), thematically similar to advanced milling vises. This method of clamping brings the high precision and repeatability of such vises to a chucking application. Such chucks offer the centering precision of traditional independent-jaw chucks with the chucking speed and ease of traditional three-jaw self-centering scroll chucks. They have expensive initial cost (compared with traditional chucks), but such initial cost pays for itself and then lowers ongoing marginal costs in commercial production-run environments. It is also possible nowadays to build CNC chucks in which the position and clamping pressure of each jaw can be precisely controlled with CNC, via closed-loop positioning and load monitoring. In essence, each jaw is one independent CNC axis, a machine slide with a leadscrew, and all four or six of them can act in concert with each other. Although this idea is conceptually interesting, the simpler chucking systems mentioned in the previous paragraph are probably a marketplace winner over this alternative for most applications, because they supply the same capabilities via a simpler, less expensive solution. Magnetic Used for holding ferromagnetic workpieces, a magnetic chuck consists