Ratchet (tool)
Ratchet and Ratchet are names for screwing , in contrast to an ordinary wrench will not be rescheduled again must if there is not enough space available to perform a complete revolution with the attached key. Instead, to gradually tighten or loosen a screw connection , the ratchet is repeatedly moved back and forth through a certain angle.
Working principle
Ratchets have the shape of a hand lever, the end of which serves as a handle, which is often covered with rubber or plastic. At the other end is the ratchet mechanism with a connecting element to the actual tool insert or attachment.
The connecting element usually has an attached square that is used to attach the tool attachment. Usually, a will socket wrench attachment used colloquially "nut" is called and eventually the positive connection to the screw or nuts manufactured.
The connecting element of push-through ratchets has a square recess into which a square can be inserted for use with common sockets. Alternatively, special tool inserts such as step wrenches can be inserted, which are used to screw fittings in sanitary engineering.
Depending on the fineness of the teeth on which the pawl runs, a working angle of 10 to 15 degrees is required in order to achieve the further rotation of the drive by one detent. With fine-tooth ratchets, an angle of rotation of around 5 degrees is sufficient, so that work can also be carried out in confined spaces. Freewheel ratchets do not need any detent.
The direction of rotation can be reversed in different ways:
- A combination of two spring-loaded pawls that point in opposite directions. Only one pawl is in use at a time, while the other is not on the toothed ring. You can switch from one pawl to the other by flipping a lever or turning a wheel.
- Instead of the pawls, a spring-loaded latched rocker is also used, which either rests on one side or the other on the toothed ring.
- Push-through ratchets with a continuous square hole get by with a single (locking) pawl. The direction of rotation is changed by repositioning the tool insert or square stub on the other side of the ratchet.
Sizes
The side length of the square drive is specified in inches as the size designation for the ratchet and the inserts that can be used with it . The most common sizes are ¼ ″ for finer work and ½ ″ for most work, e.g. B. on motor vehicles. In between is the size ⅜ ″. The sizes ¾ ″ and 1 ″ are used for heavy assembly work in the industrial sector with correspondingly high tightening torques .
This size specification in the Anglo-American measuring system only refers to the drive square and does not contain any information about the width across flats of the attached insert, which can also correspond to metric standards. A hexagon socket with a wrench size (SW) 17 is usually used with a ½ ″ ratchet, but is also available with a ¼ ″ and ¼ ″ square socket.
The length of the lever arm also differs from ratchet to ratchet. Ratchets, which can also be used as torque wrenches , usually have a very long lever arm.
Applications and examples
Ratchets are of great importance in vehicle technology as well as in machine and tool construction and assembly technology . In addition to the manually operated ratchet, similar-looking screwing tools with compressed air and, more rarely, with hydraulic drive are also used.
Electric screwdrivers, on the other hand, are more like ordinary drills , but have a larger reduction ratio in order to achieve a higher torque.
Stuck screws can often be loosened with an impact wrench .
See also
- Socket wrench
- Freewheeling (e.g. on a bicycle)
literature
- DIN 3122: 2017 Drive parts with external square for hand-operated sockets
Web links
- Tool customer: Knarren , attachment at Autoschraub.de, accessed on September 16, 2017 ( page no longer available )