Joinery is a part of
woodworkingWoodworking is the process of building, making or carving something using wood.-History:Along with stone, mud, and animal parts, wood was one of the first materials worked by early humans. Microwear analysis of the Mousterian stone tools used by the Neanderthals show that many were used to work wood...
that involves joining together pieces of
woodWood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
, to create furniture, structures, toys, and other items. Some wood joints employ fasteners, bindings, or adhesives, while others use only wood elements. The characteristics of wooden joints - strength, flexibility, toughness,appearance, etc. - derive from the properties of the joining materials and from how they are used in the joints. Therefore, different joinery techniques are used to meet differing requirements. For example, the joinery used to build a
houseA house is a building or structure that has the ability to be occupied for dwelling by human beings or other creatures. The term house includes many kinds of different dwellings ranging from rudimentary huts of nomadic tribes to free standing individual structures...
is different from that used to make
puzzleA puzzle is a problem or enigma that tests the ingenuity of the solver. In a basic puzzle, one is intended to put together pieces in a logical way in order to come up with the desired solution...
toys, although some concepts overlap.
Traditional woodworking joints
- Butt joint
A butt joint is a joinery technique in which two members are joined by simply butting them together. The butt joint is the simplest joint to make since it merely involves cutting the members to the appropriate length and butting them together. It is also the weakest because unless some form of...
; the end of a piece of wood is butted against another piece of wood. This is the simplest and weakest joint.
- Miter joint
A miter joint , sometimes shortened to miter, is a joint made by bevelling each of two parts to be joined, usually at a 45° angle, to form a corner, usually a 90° angle...
; similar to a butt joint, but both pieces have been cut at a 45 degree angle.
- Lap joint
In woodworking or metal fitting, a lap joint is a technique for joining two pieces of material by overlapping them. A lap may be a full lap or half lap....
s; one piece of wood will overlap another.
- Box joint, also called a finger joint, used for the corners of boxes. It involves several lap joints at the ends of two boards.
- Dovetail joint
A dovetail joint or simply dovetail is a joint technique most commonly used in woodworking joinery. Noted for its resistance to being pulled apart , the dovetail joint is commonly used to join the sides of a drawer to the front....
; a form of box joint where the fingers are locked together by diagonal cuts.
- Dado joint
A dado , housing or trench is a slot or trench cut into the surface of a piece of machinable material, usually wood. When viewed in cross-section, a dado has three sides...
; a slot is cut across the grain in one piece for another piece to set into; shelves on a bookshelf having slots cut into the sides of the shelf, for example.
- Groove joint
In joinery, a groove is a slot or trench cut into a member which runs parallel to the grain. A groove is thus differentiated from a dado, which runs across the grain....
; the slot is cut with the grain.
- Tongue and groove
A strong joint, the tongue and groove joint is widely used for re-entrant angles. The effect of wood shrinkage is concealed when the joint is beaded or otherwise moulded...
. Each piece has a groove cut all along one edge, and a thin, deep ridge (the tongue) on the opposite edge. If the tongue is unattached, it is considered a spline jointA spline joint can be viewed as an extended biscuit. Two boards have extended, matching grooves lined up and facing each other. The void between is filled with a thin piece of wood, forming a spline joint. This is very similar to tongue and groove. The difference is that the spline essencially...
.
- Mortise and tenon
The mortise and tenon joint has been used for thousands of years by woodworkers around the world to join pieces of wood, mainly when the adjoining pieces connect at an angle of 90°. In its basic form it is both simple and strong. Although there are many joint variations, the basic mortise and tenon...
; a stub (the tenon) will fit tightly into a hole cut for it (the mortise). This is a hallmark of Mission Style furnitureMission furniture is a style of furniture that originated in the late 19th Century. It traces its origins to a chair made by A.J. Forbes around 1894 for San Francisco's Swedenborgian Church. The term mission furniture was first popularized by Joseph P...
, and also the traditional method of jointing frame and panelFrame and panel construction is a woodworking technique often used in the making of doors, wainscoting, and other decorative features for cabinets, furniture, and homes...
members in doors, windows, and cabinets.
- Birdsmouth joint
In light frame construction, a birdsmouth joint is a woodworking joint that is generally used to connect a roof rafter to the top plate of a supporting wall...
is used in roof constructionThis article is about the type of roof construction that consists of footings and an outer weatherproof skin, as found on most domestic architecture....
. A V-shaped cut in the rafterA rafter is one of a series of sloped structural members , that extend from the ridge or hip to the downslope perimeter or eave, designed to support the roof deck and its associated loads.-Design:...
connects the rafter to the wall-plate.
- Comb Joint
A finger joint or comb joint is a woodworking joint made by cutting a set of complementary rectangular cuts in two pieces of wood, which are then glued...
a joint used as a way of conserving timber, as a means of joining random lengths of timber to be machined to a finished piece.
Nontraditional woodworking joints
- Pocket hole joinery; a hidden screw is driven into the joint at an angle.
- Joints using metal connectors, which attach to the frame with nails or screws.
Traditional ways of improving joints
- Dowels, where a small rod is used internal to a joint to both help align on glue up and permanently strengthen the joint. Traditional joints are used with natural timbers as they do not need any other materials other than the timber itself. for example: Butt joints. Dowel joints are also useful for pegging together weaker, cheaper composite materials such as laminate-faced chipboard, and where limited woodworking tools are available (since only simple drilled holes are needed to take the dowels).
Nontraditional ways of improving joints
- Biscuit joints
A biscuit joiner or sometimes plate joiner is a woodworking tool used to join two pieces of wood together. A biscuit joiner uses a small tungsten carbide tipped, circular saw blade to cut a crescent shaped hole in the opposite edges of two pieces of wood or wood composite panels...
, where a small 'biscuit' is used to help align an edge or butt joint on glue-up.
- Domino joiner, a trademarked tool similar to a biscuit joiner, where a piece larger than a biscuit has some of the advantages of dowels, and some of the advantages of biscuits.
Properties of wood
Many wood joinery techniques either depend upon or compensate for the fact that wood is anisotropic: its material properties are different along different dimensions.
Joining wood parts together must take this into account, otherwise the joint is destined to fail. Gluing boards with the grain running perpendicular to each other is often the reason for split boards, or broken joints. Furniture from the 18th century, while made by master craftsmen, did not take this into account. The result is this masterful work suffers from broken bracket feet, which was often attached with a glue block which ran perpendicular to the base pieces. The glue blocks were fastened with both glue and nails, resulting in unequal expansion and contraction between the pieces. This was also the cause of splitting of wide boards, which were commonly used during that period.
In modern woodworking it is even more critical, as heating and air conditioning cause major changes in the moisture content of the wood. All woodworking joints must take these changes into account, and allow for the resulting movement.
Strength
Wood is stronger when stressed along the
grainIn speaking of wood the term grain refers to the alternating regions of relatively darker and lighter wood resulting from the differing growth parameters occurring in different seasons . The term is used in several ways. Perhaps most important is that in woodworking techniques...
(longitudinally) than it is when stressed across the grain (radially and tangentially). Wood is a natural polymer; parallel strands of
celluloseCellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....
fibers are held together by a
ligninLignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...
binder. These long chains of fibers make the wood exceptionally strong by resisting stress and spreading the load over the length of the board. Furthermore, cellulose is tougher than lignin, a fact demonstrated by the relatively ease with which wood can be split along the grain than across it.
Different species of wood have different strength levels, and the exact strength may vary from sample to sample.
Dimensional stability
Timber expands and contracts in response to humidity, usually much less so longitudinally than in the radial and tangential directions. As
tracheophytesVascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...
, trees have
lignifiedLignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...
tissuesTissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
which transport resources such as water, minerals and photosynthetic products up and down the plant. While lumber from a harvested tree is no longer alive, these tissues still absorb and expel water causing swelling and shrinkage of the wood in kind with change in humidity. When the dimensional stability of the wood is paramount, quartersawn lumber is preferred because its grain pattern is consistent and thus reacts less to humidity.
Materials used for joining
- Joints can be designed to hold without the use of glue or fasteners; a pinned mortise and tenon is an example of this.
- Glue
This is a list of various types of glue. Historically, the term "glue" only referred to protein colloids prepared from animal flesh. The meaning has been extended to refer to any fluid adhesive....
is highly effective for joining wood when both surfaces of the joint are edge grain. A properly glued joint may be as strong or stronger than a single piece of wood. However, glue is notably less effective on end-grainIn speaking of wood the term grain refers to the alternating regions of relatively darker and lighter wood resulting from the differing growth parameters occurring in different seasons . The term is used in several ways. Perhaps most important is that in woodworking techniques...
surfaces. Animal glueAn animal glue is an adhesive that is created by prolonged boiling of animal connective tissue.These protein colloid glues are formed through hydrolysis of the collagen from skins, bones, tendons, and other tissues, similar to gelatin. The word "collagen" itself derives from Greek κόλλα kolla, glue...
is soluble in water, producing joints that can be disassembled using steamSteam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...
to soften the glue.
- Various mechanical fastener
A fastener is a hardware device that mechanically joins or affixes two or more objects together.Fasteners can also be used to close a container such as a bag, a box, or an envelope; or they may involve keeping together the sides of an opening of flexible material, attaching a lid to a container,...
s may be used, the simplest being nails and screwA screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the...
s. Glue and fasteners can be used together.
Traditional joinery
Many traditional wood joinery techniques use the distinctive material properties of
woodWood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
, often without resorting to mechanical fasteners or adhesives. While every culture in which pieces of wood are joined together to make furniture or structures has a joinery tradition, wood joinery techniques have been especially well documented and celebrated in the
ChineseAncient Chinese wooden architecture is among the least studied of any of the world's great architectural traditions from the western point of view. Although Chinese architectural history reaches far back in time, descriptions of Chinese architecture are often confined to the well known Forbidden...
, European, and Japanese traditions. The Japanese and Chinese traditions in particular include hundreds of types of joints, many of which do not use glue or nails. The Chinese have been using some of these methods for over seven thousand years.
Nontraditional joinery
Methods that are not considered traditional joinery have come about in modern times, largely to attempt to simplify the job of the woodworker for various reasons. These include biscuit joints and pocket hole joinery.
See also
- Woodworking
Woodworking is the process of building, making or carving something using wood.-History:Along with stone, mud, and animal parts, wood was one of the first materials worked by early humans. Microwear analysis of the Mousterian stone tools used by the Neanderthals show that many were used to work wood...
- Cabinet making
Cabinet making is the practice of using various woodworking skills to create cabinets, shelving and furniture.Cabinet making involves techniques such as creating appropriate joints, dados, bevels, chamfers and shelving systems, the use of finishing tools such as routers to create decorative...
- Building construction
- Chinese Wooden Architecture
Ancient Chinese wooden architecture is among the least studied of any of the world's great architectural traditions from the western point of view. Although Chinese architectural history reaches far back in time, descriptions of Chinese architecture are often confined to the well known Forbidden...
- Timber framing
Timber framing , or half-timbering, also called in North America "post-and-beam" construction, is the method of creating structures using heavy squared off and carefully fitted and joined timbers with joints secured by large wooden pegs . It is commonplace in large barns...
External links
Terms and Joints