Dog (engineering)
Encyclopedia
In engineering a dog is a tool
that prevents movement or imparts movement by offering physical obstruction or engagement of some kind. It may hold another object in place by blocking it, clamping it, or otherwise obstructing its movement. Or it may couple various parts together so that they move in unison - the primary example of this being a flexible drive to mate two shafts in order to transmit torque
.
This word usage is a metaphor
derived from the idea of a dog
(animal) biting and holding on.
, when present chainsaw dogs are mounted where the bar meets the power head. Chainsaw dogs provide stability and serve as a sort of fulcrum for swinging the bar through the item being cut.
is an accessory used on a woodworking workbench
to allow clamping of wooden items whilst being worked.
between compartments inside a ship can be closed during emergencies to seal off one compartment from another, thus sequestering water leaks, fires, or waves of air pressure and preventing them from compromising the rest of the ship's interior. The objects that are wedged against the door to hold it closed against the water or air pressure are an example of dogs. To dog the hatches means to close the hatches and dog them down (fasten them closed).
s, which hold up the firewood in a fireplace, are sometimes called dogs, firedogs, or dog irons.
that mates the engine to the transmission
in a modern manual-shift automobile is a friction clutch whose disc and pressure plate are smooth; they lock up simply through friction. However, some kinds of clutches (including the ones inside an automobile transmission) may lock up via the engagement of dogs, rather than only through friction. These clutches are called dog clutch
es and the dogs used within them are called clutch dogs.
is essentially analogous to a clutch dog. It is used to provide positive drive to a workpiece turning between centers on a lathe
. Without the dog, the cutting tool would tend to "catch", e.g. stop the workpiece from turning while the headstock center continued to rotate, possibly causing damage to the workpiece, or the lathe.
of a sewing machine feed the fabric in a linear stepping motion past the needle.
Tool
A tool is a device that can be used to produce an item or achieve a task, but that is not consumed in the process. Informally the word is also used to describe a procedure or process with a specific purpose. Tools that are used in particular fields or activities may have different designations such...
that prevents movement or imparts movement by offering physical obstruction or engagement of some kind. It may hold another object in place by blocking it, clamping it, or otherwise obstructing its movement. Or it may couple various parts together so that they move in unison - the primary example of this being a flexible drive to mate two shafts in order to transmit torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
.
This word usage is a metaphor
Metaphor
A metaphor is a literary figure of speech that uses an image, story or tangible thing to represent a less tangible thing or some intangible quality or idea; e.g., "Her eyes were glistening jewels." Metaphor may also be used for any rhetorical figures of speech that achieve their effects via...
derived from the idea of a dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
(animal) biting and holding on.
Chainsaw dogs
Although not seen on all chainsawsChainsaw
A chainsaw is a portable mechanical saw, powered by electricity, compressed air, hydraulic power, or most commonly a two-stroke engine...
, when present chainsaw dogs are mounted where the bar meets the power head. Chainsaw dogs provide stability and serve as a sort of fulcrum for swinging the bar through the item being cut.
Shutter dogs
Functional exterior window shutters (which can be swung shut whenever storms approach in order to protect the window glass from impact by wind-blown debris) are held open during pleasant weather by wrought-iron or cast-iron dogs, which are called shutter dogs.Bench dogs
A bench dogBench dog
A bench dog is an accessory used on a woodworking workbench to allow clamping of wooden items whilst being worked.At its most basic a bench dog is simply a peg which is installed in a corresponding dog hole in the top of a bench...
is an accessory used on a woodworking workbench
Workbench (woodworking)
A Workbench is a table used by woodworkers to hold workpieces while they are worked by other tools. There are many styles of woodworking benches, each reflecting the type of work to be done or the craftsman's way of working...
to allow clamping of wooden items whilst being worked.
Ladder dogs
Ladder dogs are the parts of a ladder that hold the ladder at a certain height, and articulate against pawls to allow adjustment.Hatch dogs
The doors that allow passage through bulkheadsBulkhead (partition)
A bulkhead is an upright wall within the hull of a ship or within the fuselage of an airplane. Other kinds of partition elements within a ship are decks and deckheads.-Etymology:...
between compartments inside a ship can be closed during emergencies to seal off one compartment from another, thus sequestering water leaks, fires, or waves of air pressure and preventing them from compromising the rest of the ship's interior. The objects that are wedged against the door to hold it closed against the water or air pressure are an example of dogs. To dog the hatches means to close the hatches and dog them down (fasten them closed).
Firedogs (alias dog irons, andirons)
AndironAndiron
An andiron is a horizontal iron bar upon which logs are laid for burning in an open fireplace. They are usually used in pairs to build up a firedog, sometimes called a dog or dog-iron. In older eras An andiron (older form anderne; med. Lat. andena, anderia) is a horizontal iron bar upon which logs...
s, which hold up the firewood in a fireplace, are sometimes called dogs, firedogs, or dog irons.
Clutch dogs
The clutchClutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...
that mates the engine to the transmission
Transmission (mechanics)
A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...
in a modern manual-shift automobile is a friction clutch whose disc and pressure plate are smooth; they lock up simply through friction. However, some kinds of clutches (including the ones inside an automobile transmission) may lock up via the engagement of dogs, rather than only through friction. These clutches are called dog clutch
Dog clutch
A dog clutch is a type of clutch that couples two rotating shafts or other rotating components not by friction but by interference. The two parts of the clutch are designed such that one will push the other, causing both to rotate at the same speed and will never slip.Dog clutches are used where...
es and the dogs used within them are called clutch dogs.
Lathe dogs
The lathe dog (or lathe carrier)Lathe carrier
A lathe dog, also known as a lathe carrier, is a device that clamps around the workpiece and allows the rotary motion of the machine's spindle to be transmitted to the workpiece....
is essentially analogous to a clutch dog. It is used to provide positive drive to a workpiece turning between centers on a lathe
Lathe (metal)
A metal lathe or metalworking lathe is a large class of lathes designed for precisely machining relatively hard materials. They were originally designed to machine metals; however, with the advent of plastics and other materials, and with their inherent versatility, they are used in a wide range of...
. Without the dog, the cutting tool would tend to "catch", e.g. stop the workpiece from turning while the headstock center continued to rotate, possibly causing damage to the workpiece, or the lathe.
Feed dogs
The feed dogsFeed dogs
Feed dogs are the critical component of a "drop feed" sewing machine. A set of feed dogs typically resembles two or three short, thin metal bars, crosscut with diagonal teeth, which move back and forth in slots in a sewing machine's needle plate...
of a sewing machine feed the fabric in a linear stepping motion past the needle.