A pin chuck
is a small work holding device. It is often used to hold small drills (<1 mm) that would not be held securely in a normal (1 mm–13 mm) drill chuck. The drill is inserted into the pin chuck and tightened, the pin chuck is then inserted into the larger drill chuck so that the operation can continue.
Pin chucks are also found on high speed rotary tools, such as die grinders and jig grinders.