A brace and bit is one type of hand hand operated tool that was used to create holes prior to the development of power drills. The brace component consists of a handle that is bent in such a way that the operator can hold it in place with one hand and rotate it around a central axis with the other. One end of the brace is typically fitted with a chuck that a drill bit or other tool can be inserted into. When the brace and bit is turned, it can drill a hole, turn a fastener, or perform any other similar work that involves a circular motion.
The first brace and bit tools were probably used in the early part of the 15th century, as evidenced in artwork that dates to that time. A brace uses a type of compound crank or single throw crankshaft in the handle, and these technologies also date to about that time. The use of a compound crank gives a brace and bit more torque than other hand driven drills, which can allow large, deep holes to be driven.
There are a few drawbacks to the brace and bit. Other types of hand cranked drills can typically achieve higher rotational speeds at lower torques, which can allow holes to be drilled more quickly. The motion of rotating the single throw crankshaft of a brace can also cause wobble, which tends to make these tools poorly suited to precision drilling. Other types of hand cranked drills or power drills are better suited to those applications.
Many braces include a number of additional features that can make the tools more useful in particular situations. A ratcheting function is often included, which can allow the chuck head to spin freely when the crank is turned in one direction but engage when it is turned in the other. This can allow holes to be drilled in tight quarters, though it is also very useful in quickly removing or installing screws. Another useful feature found in some braces is a joint where the crank and chuck meet, which can be adjusted if the situation warrants.
Both handles of a brace typically feature freely rotating grips. This allows the device to be operated rapidly without creating friction between the tool and the hands of the operator. If the tool lacks this feature, the operator will typically need to grip it lightly and rotate it slowly to avoid injuring his hands.