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Wednesday 24 February 2016

WOODWORKING JOINT

Joinery is a part of woodworking that involves joining together pieces of timber or lumber, to produce more complex 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 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 puzzle toys, although some concepts overlap.


A worker uses a mortising machine to shape timber framing joints

List of  wood joints


A worker uses a large circular saw to cut joints.

Traditional woodworking jointsEdit

JointjointDescription
Butt jointThe end of a piece of wood is butted against another piece of wood. This is the simplest and weakest joint. Of those, there is the a) T-butt, b) end-to-end butt, c) T-lap d) Miter butt and e) edge-to-edge butt.
Overlap joint see lap jointThe end of a piece of wood is laid beside and connected to another piece of wood. This is the next simplest and weakest joint.
Bridle joint
Joinery-CornerBriddleJoint.svg
Also known as open tenon, open mortise and tenon, or tongue and fork joints, this joint is where the through mortise is open on one side and forms a fork shape. The mate has a through tenon or necked joint. Bridle joints are commonly used to join rafter tops, also used in scarf jointsand sometimes sill corner joints in timber framing.
Dowel joint
Woodworking-joint-butt-dowel.gif
The end of a piece of wood is butted against another piece of wood. This is reinforced with dowel pins. This joint is quick to make with production line machinery and so is a very common joint in factory-made furniture.
Mitre joint
Mitre-joint.png
Similar to a butt joint, but both pieces have been bevelled (usually at a 45 degree angle).
Finger joint
Boxjoint.png
Also known as a box joint, is a corner joint with interlocking fingers. Receives pressure from two directions.
Dovetail joint
Joinery-throughdovetail.svg
A form of box joint where the fingers are locked together by diagonal cuts. More secure than a finger joint.
Dado joint
Dado joint.png
Also called a housing joint or trench joint, 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
Woodworking-joint-groove.gif
Like the dado joint, except that the slot is cut with the grain.
Tongue and groove
Dusheme.jpg
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 joint.
Mortise and tenon
Mortise tenon.png
A stub (the tenon) will fit tightly into a hole cut for it (the mortise). This is a hallmark of Mission Style furniture, and also the traditional method of jointing frame and panel members in doors, windows, and cabinets. This joint is a good strong joint to use.
Birdsmouth joint
BirdsMouthJoint.jpg
Also called a bird's beak cut, this joint used in roof construction. A V-shaped cut in the rafter connects the rafter to the wall-plate.[1]
Cross Lap
Joinery-SimpleHalved.svg
A joint in which the two members are joined by removing material from each at the point of intersection so that they overlap.
Splice joint
Splice-joint.svg
A joint used to attach two members end to end.

Non traditional wood working jointsEdit

-JointImageDescription
Wooden (or integral) connectorsPocket hole joinery
Pocket-hole joint being assembled.gif
A hidden screw is driven into the joint at an angle.
biscuitA wooden disc is driven into the joint at an angle.
Metal connectorsJoints using metal connectors that attach to the frame with nails or screws.
Floating tenon jointSee Mortise and tenon
stitch and glue
StitchAndGlue.svg

Traditional ways of improving 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 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).

A doweled joint

Non-traditional ways of improving joints

  • Biscuit joints :  A small 'biscuit' is used to help align an edge or butt joint when gluing.
  • 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.
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

  • Joints can be designed to hold without the use of glue or fasteners; a pinned mortise and tenon is an example of this.
  • 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 glue.
Metal plates are often incorporated into the design where the timber alone would not be strong enough for a given load

  • Various mechanical fasteners may be used, the simplest being nails and screws. Glue and fasteners can be used together.

Pin-connected post and beam house framing

Traditional Joinery

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 together to make furniture or structures has a joinery tradition, wood joinery techniques have been especially well documented and celebrated in the Indian, Chinese, European, and Japanese traditions. Because of the actual 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 thousand 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 pre-cleaned with solvents and attached using modern glues.

Non traditional 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.

- Wikipedia 

FINGER JOINT

finger joint, also known as a comb or box joint, is a woodworking joint made by cutting a set of complementary rectangular cuts in two pieces of wood, which are then glued. To visualize a finger joint simply interlock the fingers of your hands at a ninety degree angle; hence the name "finger joint." It is stronger than a butt joint or lap joint and often contributes to the aesthetics (appearance) of the piece.
Finger joint or box combing
Alternate names include box-pin joint or box joint.
Applications
A tapered or scarfed finger joint is the most common joint used to form long pieces of lumber from solid boards; the result is finger-jointed lumber.
The finger joint can also be invaluable when fixing tables and chairs and also can be used in such things as floor boards, timber roof and door construction. This is also used in design technology for students. Finger joints can be hard to make without the right tools.
- Wikipedia 

LAMINATED VENEER LUMBER

Laminated veneer lumber (LVL) is an engineered wood product that uses multiple layers of thin wood assembled with adhesives. It is typically used for headers, beams, rimboard, and edge-forming material. LVL offers several advantages over typical milled lumber: Made in a factory under controlled specifications, it is stronger, straighter, and more uniform. Due to its composite nature, it is much less likely than conventional lumber to warp, twist, bow, or shrink.
A short piece of laminated veneer lumber cut in section to show composing multiple layers of thin wood
Laminated veneer lumber detail
Laminated veneer lumber is similar in appearance to plywood without cross bands and is typically rated by the manufacturer for elastic modulus and allowable bending stress. Common elastic moduli are 1,800,000 psi (12,000 MPa); 1,900,000 psi (13,000 MPa); and 2,000,000 psi (14,000 MPa); and common allowable bending stress values are 2,800 psi (19 MPa); and 3,000 psi (21 MPa).
LVL is commonly manufactured in North America by companies that also manufacture I-joists. LVL is manufactured to sizes compatible with the depth of I-joist framing members for use as beams and headers. Additionally, some manufacturers further cut LVL into sizes for use as chord-members on I-joists. In 2012, North American LVL manufacturers produced more than 43.4 million cubic feet (1.2 million cubic meters) of LVL in 18 different facilities, and in 2013 the production increased with more than 14%.
Because it is specifically sized to work with I-joist floor framing, residential builders and building designers like the combination of I-joist and LVL floor and roof assemblies. LVL is a highly reliable building material that provides many of the same attributes associated with large sized timbers.
Structure Laminated Lumber

LVL belongs to the category of engineered wood called structural composite lumber. Other members of this category are parallel strand lumber (PSL) and laminated strand lumber (LSL). All members of this category are strong and predictable, and are thus interchangeable for some applications. PSL is made from veneers that are cut up into long strands and oriented parallel to its length before compressed into its final shape. LSL is also made from strands rather than veneer, although the strands are shorter and aligned with less precision than PSL and is created as billets that are like a thick version of oriented strand board. 

Innowood 

Innowood is a composite reconstituted wood based material primarily made of timber used for internal and external applications. It is made from recycled wood waste and polymeric resins used in composite building and architectural products in Australia. The profile of Innowood has natural timber finish and texture with lesser weight. Innowood was introduced by an Australian John Kozlowski, founder of Innowood Australia Pty Ltd and it was used in composite building and products to reduce installation costs by concealed fixing and fastening systems.

Parallel Strand Lumber 


Parallam is the brand name for an engineered wood product invented, developed, commercialized and patented by MacMillan Bloede (now Weyerhaeuser) .The generic name for the product is parallel strand lumber (PSL). Parallam is made from clipped veneer strands laid in parallel alignment and bonded with adhesive. It is used for beams, headers, columns, and posts, among others uses. Parallam is the world's only commercially manufactured and marketed parallel strand lumber product. It is a member of the structural composite lumber (SCL) family of engineered wood products.
The product is manufactured as a 12" x 12" or 12" x 18" billet in a rectangular cross-section, which is then typically sawn and trimmed to smaller cross-sectional sizes. The beams are continuously formed, so the length of the beam is only limited to the maximum length that can be handled and transported. Typical thicknesses are 3½", 5¼” or 7"; typical depths are 9½", 11⅞" 14", 16" & 18". Typically the beams are made to a maximum length of 60 feet.
The design values for Parallam, in bending, tension parallel to grain and compression parallel to grain are greater than sawn lumber made from the same or similar species. This is because knots and other imperfections are randomly dispersed throughout the product so that strength variability from one piece to another is less than in solid-sawn wooden beams. Since materials are commonly graded to the lowest 5th percentile of the material's strength curve, this gives Parallam much higher usable strength. Parallam can be made from any wood species, but Douglas-fir, southern pine, western hemlock, and yellow-poplar are commonly chosen because of their superior strength.

- Wikipedia 

GLUED LAMINATED TIMBER

Glued laminated timber, also called glulam, is a type of structural timber product comprising a number of layers of dimensioned timber bonded together with durable, moisture-resistant structural adhesives. In North America the material providing the laminations is termed laminating stock or lamstock.
By laminating a number of smaller pieces of timber, a single large, strong, structural member is manufactured from smaller pieces. These structural members are used as vertical columns or horizontal beams, as well as curved, arched shapes. Glulam is readily produced in curved shapes and it is available in a range of species and appearance characteristics to meet varied end-use requirements. Connections are usually made with bolts or plain steel dowels and steel plates.
Glulam optimizes the structural values of a renewable resource – wood. Because of their composition, large glulam members can be manufactured from a variety of smaller trees harvested from second- and third-growth forests and plantations. Glulam provides the strength and versatility of large wood members without relying on the old growth-dependent solid-sawn timbers. As with other engineered wood products, it reduces the overall amount of wood used when compared to solid sawn timbers by diminishing the negative impact of knots and other small defects in each component board.
Glulam has much lower embodied energy than reinforced concrete and steel, although of course it does entail more embodied energy than solid timber. However, the laminating process allows timber to be used for much longer spans, heavier loads, and complex shapes. Glulam is two-thirds the weight of steel and one sixth the weight of concrete – the embodied energy to produce it is six times less than the same suitable strength of steel. Glulam can be manufactured to a variety of straight and curved configurations so it offers architects artistic freedom without sacrificing structural requirements.
The high strength and stiffness of laminated timbers enable glulam beams and arches to span large distances without intermediate columns, allowing more design flexibility than with traditional timber construction. The size is limited only by transportation and handling constraints.


Glulam frame used for a roof structure
Glulam and Steel
A 2002 case study comparing energy use, greenhouse gas emissions and costs for roof beams found it takes two to three times more energy and six to twelve times more fossil fuels to manufacture steel beams than it does to manufacture glulam beams. It compared two options for a roof structure of a new airport in Oslo, Norway – steel beams and glulam spruce wood beams. The life cycle greenhouse gas emission is lower for the glulam beams. If they are burned at the end of their service life, more energy can be recovered than was used to manufacture them. If they are landfilled, the glulam beams result in greater greenhouse gas emissions than the steel beams. The cost of the glulam beams is slightly lower than the steel beams.
History 
One of the earliest still-standing glulam roof structures is generally acknowledged to be the assembly room of King Edward VI College, a school in Bugle Street, Southampton, England, dating from 1866, designed by Josiah George Poole. The building is now the Marriage Room of Southampton Register Office.
Glulam dome roofing the tower of the University of Zurich, built using the Hetzer system in 1911.
Two churches in Northumberland are now thought to have the earliest extant uses: Holy Trinity, Cambo (1842), and Holy Trinity, Horsley (1844), and four 1850s Merseyside churches also feature laminated timbers: St Mary, Grassendale, St Luke, Formby, St Paul, Tranmere and Holy Trinity, Parr Mount, St Helens.
Richmond Olympic Oval intern view
The first industrial patented use was in Weimar, Germany. Here in 1872 Otto Hetzer set up a steam sawmill and carpentry business in Kohlstrasse. Beginning in 1892, he took out a series of patents. DRP No. 63018 was for a ventilated timber floor deck that could be tightened laterally after installation, to compensate for shrinkage. Hetzer continued to patent various ingenious systems, but the first of these that could be compared with subsequently standardised horizontal glulam was DRP No. 197773, dated 1906. This entailed vertical columns which transitioned into curved glued laminated eaves zones, and then became sloped rafters, all in a single laminated unit. Each component, bonded under pressure, comprised three or more horizontally arranged laminations.
In other words, the glulam portal frame was born. In 1895, Hetzer moved his company to Ettersburger Strasse, still in Weimar. At the height of production, in around 1917, he employed about 300 workers, and Müller includes a fine engraving of the railway sidings and works in 1921.
In 1909, the Swiss engineering consultants Terner & Chopard purchased permission to use Hetzer's patent, and employed glulam in a number of projects. These included the former Hygiene Institute, Zurich, 1911, now the main building of the university, where the bell-shaped roof dome is still to be seen.
The technology arrived in North America in 1934 when Max Hanisch, Sr., who had worked with Hetzer at the turn of the century, formed a firm in Peshtigo, Wisconsin to manufacture structural glued laminated timber.
A significant development in the glulam industry was the introduction of fully water-resistant phenol-resorcinol adhesive in 1942. This allowed glulam to be used in exposed exterior environments without concern of gluline degradation. The first U.S. manufacturing standard for glulam was Commercial Standard CS253-63, which was published by the Department of Commerce in 1963. The most recent standard is ANSI/AITC Standard A190.1–02, which took effect in 2002.
The roof of the Centre Pompidou-Metz museum is composed of sixteen kilometers of glued laminated timber. It represents a 90-metre wide hexagon with a surface area of 8,000 m². The glued laminated timber motif forms hexagonal wooden units resembling the cane-work pattern of a Chinese hat.
Sport Structures
Sports structures are a particularly suitable application for wide-span glulam roofs. This is supported by the light weight of the material, combined with the ability to furnish long lengths and large cross-sections. Prefabrication is invariably employed and the structural engineer needs to develop clear method statements for delivery and erection at an early stage in the design. The PostFinance Arena is an example of a wide-span sports stadium roof using glulam arches reaching up to 85 metres. The structure was built in Bern in 1967, and has subsequently been refurbished and extended.
The roof of the Richmond Olympic Oval, built for speed skating events at the 2010 Winter Olympic Games in Vancouver, British Columbia, features one of the world's largest clearspan wooden structures. The roof includes 2,400 cubic metres of Douglas-fir lamstock lumber in glulam beams. A total of 34 yellow-cedar glulam posts support the overhangs where the roof extends beyond the walls.
Glulam Bridges
Pressure-treated glulam timbers or timbers manufactured from naturally durable wood species are well suited for creating bridges and waterfront structures. Wood’s ability to absorb impact forces created by traffic and its natural resistance to chemicals, such as those used for de-icing roadways, make it ideal for these installations. Glulam has been successfully used for pedestrian, forest, highway, and railway bridges. An example in North America of a glulam bridge is at Keystone Wye, South Dakota, constructed in 1966–1967.
Glulam bridge crossing Montmorency RiverQuebec.
The Kingsway Pedestrian Bridge in Burnaby, British Columbia, Canada, is constructed of cast-in-place concrete for the support piers, structural steel and glulam for the arch, a post tensioned pre-cast concrete walking deck, and stainless steel support rods connecting the arch to the walking deck.
Sneek, The Netherlands. Heavy-traffic Accoya Glulam Bridge

U.S Manufacturing

In 2015, a lumber mill in Riddle, OR, operated by D.R. Johnson Lumber, began production of cross laminated timber panels designed to be used to build multi-story commercial and residential buildings. It was the first U.S. company to produce the panels as components to replace steel and concrete as basic building materials for commercial and residential projects. Architects and developers in Portland, OR, encouraged the production and said they intended to use them for projects already in the planning stages.

- Wikipedia 

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