Joinery (woodworking)

Joinery is a part of woodworking that involves joining pieces of wood, engineered lumber, or synthetic substitutes (such as laminate), to produce more complex items. Some woodworking joints employ mechanical fasteners, bindings, or adhesives, while others use only wood elements (such as dowels or plain mortise and tenon fittings).

The characteristics of wooden joints - strength, flexibility, toughness, appearance, etc. - derive from the properties of the materials involved and the purpose of the joint. Therefore, different joinery techniques are used to meet differing requirements. For example, the joinery used to construct a house can be different from that used to make cabinetry or furniture, although some concepts overlap. While a form of carpentry elsewhere, in British English usage it is distinguished from it, which is considered to be a form of structural timber work.

History

Many traditional wood joinery techniques use the distinctive material properties of wood, often without resorting to mechanical fasteners or adhesives. While every culture in which pieces of wood are joined to make furniture or structures has a joinery tradition, wood joinery techniques have been especially well-documented, and are celebrated, in the Indian, Chinese, European, and Japanese traditions. Because of the physical existence of Indian and Egyptian examples, we know that furniture from the first several dynasties show the use of complex joints, like the Dovetail, over 5,000 years ago. This tradition continued to other later Western styles. The 18th-century writer Diderot included over 90 detailed illustrations of wood joints in his comprehensive encyclopedia. While Western techniques focused on concealment of joinery, the Eastern societies, though later, did not attempt to "hide" their joints. The Japanese and Chinese traditions in particular required the use of hundreds of types of joints. The reason was that nails and glues used did not stand up well to the vastly fluctuating temperatures and humid weather conditions in most of Central and South-East Asia. As well, the highly resinous woods used in traditional Chinese furniture do not glue well, even if they are cleaned with solvents and attached using modern glues.

As with all trades new developments have evolved to help speed, simplify, or improve joinery. These include "biscuit" and "domino" joints, and pocket screw joinery.

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.

This must be taken into account when joining wood parts together, 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 grain (longitudinally) than it is when stressed across the grain (radially and tangentially). Wood is a natural composite material; parallel strands of cellulose fibers are held together by a lignin 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 relative ease with which wood can be split along the grain compared to 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 tracheophytes, trees have lignified tissues 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, quarter-sawn or rift-sawn lumber is preferred because its grain pattern is consistent and thus reacts less to humidity.

Materials used for joining

* Dowels can secure wood joints hold without the use of glue or mechanical fasteners, as in a pinned mortise and tenon.
* Glue is highly effective for joining timber 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-grain surfaces. Animal glue is soluble in water, producing joints that can be disassembled using steam to soften the bond.
* Various mechanical fasteners may be used, the simplest being nails and screws. Glue and fasteners can be used together.

Reinforcing joints

* Dowel: A small rod is used internal to a joint both to help align and to strengthen the joint. Traditional joints are used with natural timbers as they do not need 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).

* Biscuit joints: A small preformed wooden 'biscuit' is inserted in a pre-cut slot to help align an edge or butt joint when gluing.
* Domino joiner: A trademarked form of biscuit joiner, where a larger piece of preformed wood than a traditional biscuit - referred to as a "domino" - has some of the advantages of dowels and some of biscuits. Monday, June 22, 2020

Types of wood joints

Traditional

Modern

See also

Footnotes

References

* Lee A. Jesberger (2007). ''Woodworking Terms and Joints''. Pro Woodworking Tips.com
* Bernard Jones (Ed.) (1980). ''The Complete Woodworker''.
* Peter Korn (1993). ''Working with Wood''.
* Sam Allen (1990). ''Wood Joiner's Handbook''. Sterling Publishing.
* Wolfram Graubner (1992). ''Encyclopedia of Wood Joints''. Taunton Press.
* US Forestry Service (1985) ''Water Repellency and Dimensional Stability of Wood'' http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr50.pdf

External links

Pro Woodworking Tips - Woodworking

British Woodworking Federation
- not for profit woodworking body advice on joinery in the UK
;Terms and Joints

Craftsmanspace
* List of French timber framing joints, in French language

custom furniture dubai

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