movement, usually by pushing the tapered closing ring toward the collet rather than pulling the collet into the ring. Such non-draw-in types are often called "dead-length" or "non-draw-in" collet chucks. Draw-in is not always a problem, but avoiding it can be helpful on some work where failing to account for it might result in inaccuracy on part overall length, shoulder lengths, etc. Collets are most commonly found on milling machines, lathes, wood routers, precision grinders, and certain handheld power tools such as die grinders and rotary tools. There are many different systems, common examples being the ER, 5C, and R8 systems. Collets can also be obtained to fit Morse or Brown and Sharpe taper sockets. Typically collets offer higher levels of precision and accuracy than self-centering chucks, and have a shorter setting up time than independent-jaw chucks. The penalty is that most collets can only accommodate a single size of workpiece. An exception is the ER collet which typically has a working range of 1 mm (about 0.04 in). Collets usually are made to hold cylindrical work, but are available to hold square, hexagonal or octagonal workpieces. While most collets are hardened, "emergency" collets are available that can be machined to special sizes or shapes by the user. These collets can be obtained in steel, brass, or nylon. Step collets are available that are machinable to allow holding of short workpieces that are larger than the capacity of normal collets. Special Direct System (SDS) Developed by Bosch in 1975 for hammer drills, the SDS System uses an SDS Shank which is a cylindrical shank with indentations to be held by the chuck. A tool is inserted into the chuck, and is locked in place until the lock is released. The rotary force is transmitted through wedges that fit into two or three open grooves. The bit is free to move a short distance and the hammer action moves the bit up and down within the chuck. Two sprung balls fit into closed grooves, allowing movement whilst retaining the bit. There are four standard sizes with varying shank diameters: SDS Quick A 6 mm shank with two open grooves interacting with the driving wedges and two closed grooves held by locking balls. This is the newest size introduced in 2011 for the Bosch Uneo series and takes concrete drills up to 10 mm diameter. SDS-Plus A 10 mm shank with two