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A carriage bolt (also called coach bolt and round-head square-neck bolt) is a form of bolt used to fasten metal to metal or, more commonly, wood to metal. Also known as a cup head bolt in Australia and New Zealand.
It is distinguished from other bolts by its shallow mushroom head and the fact that the cross-section of the shank, though circular for most of its length (as in other kinds of bolt), is square immediately beneath the head. This makes the bolt self-locking when it is placed through a square hole in a metal strap. This allows the fastener to be installed with only one tool, a spanner or wrench, working from one side. The head of a carriage bolt usually is a shallow dome. The shank has no threads; and its diameter equals the side of the square cross-section.
The carriage bolt was devised for use through an iron strengthening plate on either side of a wooden beam, the squared part of the bolt fitting into a square hole in the ironwork. It is common to use a carriage bolt to bare timber, the square section giving enough grip to prevent rotation.
The carriage bolt is used extensively in security applications, such as locks and hinges, where the bolt must be removable from one side only. The smooth, domed head and square nut below prevent the carriage bolt from being gripped and rotated from the insecure side.
The plough bolt is a flush-fitting carriage bolt, whose head is countersunk beneath the surface of the wood. The plough bolt was devised to hold replaceable
A carriage bolt (also called coach bolt and round-head square-neck bolt) is a form of bolt used to fasten metal to metal or, more commonly, wood to metal. Also known as a cup head bolt in Australia and New Zealand.
It is distinguished from other bolts by its shallow mushroom head and the fact that the cross-section of the shank, though circular for most of its length (as in other kinds of bolt), is square immediately beneath the head. This makes the bolt self-locking when it is placed through a square hole in a metal strap. This allows the fastener to be installed with only one tool, a spanner or wrench, working from one side. The head of a carriage bolt usually is a shallow dome. The shank has no threads; and its diameter equals the side of the square cross-section.
The carriage bolt was devised for use through an iron strengthening plate on either side of a wooden beam, the squared part of the bolt fitting into a square hole in the ironwork. It is common to use a carriage bolt to bare timber, the square section giving enough grip to prevent rotation.
The carriage bolt is used extensively in security applications, such as locks and hinges, where the bolt must be removable from one side only. The smooth, domed head and square nut below prevent the carriage bolt from being gripped and rotated from the insecure side.
Timber bolt
Closely related to the carriage bolt is the timber bolt (also called ''mushroom-head bolt'' and ''dome-head bolt''), meant to fasten wood to wood (rather than metal to wood), for use with large wood planks and structures. It has a domed head that is proportionally wider than that of a carriage bolt. Instead of the carriage bolt's square part of the shank immediately under the head, the timber bolt has four fillets, whose sharp corners grip the edge of the hole in the wood to prevent rotation.Plough bolt
The plough bolt is a flush-fitting carriage bolt, whose head is countersunk beneath the surface of the wood. The plough bolt was devised to hold replaceable ploughshare
In agriculture, a plowshare ( US) or ploughshare ( UK; ) is a component of a plow (or plough). It is the cutting or leading edge of a moldboard which closely follows the coulter (one or more ground-breaking spikes) when plowing.
The plowshar ...
s to the mouldboard
A plough or plow (Differences between American and British spellings, US; both ) is a farm tool for loosening or turning the soil before sowing seed or planting. Ploughs were traditionally drawn by oxen and horses, but in modern farms are draw ...
s of iron plough
A plough or plow ( US; both ) is a farm tool for loosening or turning the soil before sowing seed or planting. Ploughs were traditionally drawn by oxen and horses, but in modern farms are drawn by tractors. A plough may have a wooden, iron or ...
s. The share, the fastest-wearing part of the plough, would be replaced several times over the life of the plough. Such bolts continue to be used to hold shovel
A shovel is a tool used for digging, lifting, and moving bulk materials, such as soil, coal, gravel, snow, sand, or ore.
Most shovels are hand tools consisting of a broad blade fixed to a medium-length handle. Shovel blades are usually made o ...
s onto cultivator
A cultivator is a piece of agricultural equipment used for secondary tillage. One sense of the name refers to frames with ''teeth'' (also called ''shanks'') that pierce the soil as they are dragged through it linearly. It also refers to mac ...
s.
See also
*Coach screw
A screw and a bolt (see '' Differentiation between bolt and screw'' below) are similar types of fastener typically made of metal and characterized by a helical ridge, called a ''male thread'' (external thread). Screws and bolts are used to fa ...
or lag bolt, a square- or hex-headed screw
A screw and a bolt (see '' Differentiation between bolt and screw'' below) are similar types of fastener typically made of metal and characterized by a helical ridge, called a ''male thread'' (external thread). Screws and bolts are used to fa ...
with a tapered woodscrew thread.
References
{{Reflist Threaded fasteners