If you take a closer look at the massive vintage furniture or doors, a beautiful and uniform texture catches the eye: the product seems to be carved from one large piece of wood. Only upon closer examination, it is possible to single out individual planks, which make up the overall surface.
Previously, furniture was not made, as it is done today, from thick boards. It's just that the carpenters were more skilled. From many thin boards, they could make a large panel with a perfectly smooth surface. Although the tree is known to live its contented turbulent life even when it is no longer rooted to the ground. It is exposed to temperature and humidity, as well as mechanical stress, as a result of which it can unexpectedly show its “character”.
The technique of joining boards so that they remain even and smooth for a long time is called butt-to-length joining.
You need to carefully consider each plank and compare its texture with the texture of neighboring parts: the wood fibers of each part should run in the opposite direction compared to the fibers of neighboring planks. So one board "locks" the other.
The nature of the texture depends on which part of the trunk the board is cut from - from the middle or the extreme. The boards can be laid out in different ways: in one case, so that the surface will seem like a cut of one trunk, in the other, by mixing the boards, create an unusual pattern.
But in any case, when fitting, the boards should be placed against each other so that a wavy pattern is obtained. Therefore, it is very difficult to achieve the effect of a “whole tree” and at the same time “lock” the tree. After all, alternately the front (facing the core of the tree), then the wrong side (facing the bark) side of the boards are visible.
In order for the boards to fit snugly together along the length, the edges must be absolutely straight. It is necessary to vertically fix the board between two guide boards and process the surface with a planer. Treat the wood immediately, without delay - when the humidity changes, it can deform again.
On the tabletop, assembled from boards, they used to judge the skill of the carpenter. The ability to connect boards end-to-end along the length can come in handy today. We will show and tell you how it's done.
Marking and gluing
How to properly connect the boards along the length of the insert strip
The plank reinforces the joint along its entire length, while performing two functions: it doubles the area of the joint areas covered with glue, as it penetrates inside both boards, which gives the joint additional strength, and due to the opposite direction of the fibers in the plank in relation to the fibers in the main parts connection is more resistant to stress.
Use of plywood
For a plank that needs to be very thin, plywood is the most suitable material. If, for example, you take a plank of solid wood, then the arrangement of the fibers in the plank and the boards will be parallel. In this case, high bond strength will be achieved, but the bar itself will not withstand the load and will break if the boards begin to sag. You can use a bar with a transverse direction of the fibers. It well withstands the load during the deflection of the boards and gives greater strength to the connection, but such strips are limited in length and extremely unreliable under longitudinal loads. The multi-layered plywood compensates for the shortcomings of the solid wood planks, providing strength to the joint.
An alternative to the rail is plug-in spikes, which are placed with a landing on glue at a distance of 10-20 cm from each other. First, a hole for the spikes is drilled in one board, then the location of the spikes on the other board is marked with special markers.
The left bar is longer, the middle one is thicker than necessary, the right one is done correctly. It should be shorter than the overall height of the grooves to leave room for the adhesive.
Blind connection using a plywood plank. The bar is completely hidden, and the boards at the ends remain intact.
Timber products such as beams, boards or bars are mainly produced in a specific size, but often the construction may require material that has a greater length, width or thickness. For this reason, several types of connections are used to achieve the required size, using notches made by specialized equipment or manual method by markup.
Width Connections
After fastening boards with a small width, they acquire a shield with the dimensions required for production. There are several methods for docking:
1)Docking on a smooth fugue;
in this docking method, any board or rail is referred to as a plot, and the formed seam is referred to as a fugue. Jointing can be considered of high quality only when there are no gaps between the joints of the edges of adjacent boards.
2)Rail fastening;
grooves are selected along the edges of the plot and slats are inserted into them, fastening the boards to each other. The thickness of the lath and the width of the groove itself cannot exceed 1/3 of the thickness of the timber used
3) Quarter fastening;
in joined plots, completely along the entire length, quarters are selected. With this method, quarters cannot exceed 50% of the thickness of the plot itself.
4) Docking type in a groove and a crest (rectangular and triangular);
this type of docking provides for the presence of a groove on one edge of the plot, and a ridge on the opposite edge, the shape of which can be either rectangular or triangular. At the same time, the latter is used infrequently, due to the lower level of the fortress. This kind of docking is quite in demand and is often used in the manufacture of parquet. Lack of bonding - lower cost savings due to using more boards
5) Fastening type "dovetail";
this type of docking is somewhat similar to the previous version, but only the crest here has a trapezoid shape, similar to the tail of swallows. Hence the name of the mounting method.
Connection of boards into shields: a - on a smooth fugue, b - in a quarter, c - on a rail, d - in a groove and a rectangular comb, e - in a groove and a triangular comb, e - in a dovetail.
Also, in the production of wood panels, dowels, a comb with a glued into the end rail and tips into the groove are often used. Laths for pasting can have a rectangular shape or triangular. When using keys, it is better to prefer a dovetail groove. All this is necessary for the manufacture of high-quality wood panels.
Shields: a - with dowels, 6 - with a tip in the groove and comb, c - with a glued rail in the end, d - with a glued triangular rail, e - with a glued triangular rail.
Length connection
The most popular methods of joining along the length are: close, such as a groove and a ridge, fastening with a “mustache”, a notched type of adhesive bonding, a quarter, and also a fastening on a rail. The most actively used docking is of the gear type, due to its extremely high level of strength.
The connection of the bars along the length: a - end-to-end, b - in the groove and ridge, c - on the mustache, d, e - on the toothed adhesive connection, e - in a quarter, g - on the rail.
Also, the boards can be joined by splicing, when the timber segments are joined together in length. This is done in several ways. For example, in half a tree or a cut of an oblique type, an overhead lock of an oblique type and a straight one, close, as well as a tension lock of both a direct type and an oblique one. When splicing using the half-tree method, the required length must be 2-2.5 of the bar thickness indicator. To increase the level of reliability, dowels are used. For example, a similar option can be observed when building cottages from timber.
When using a cut of an oblique type with trimming the ends, the size should be equal to 2.5-3 of the thickness of the bar. It is also fixed with dowels.
Fastening with an overhead lock of an oblique or direct type is used in those structures where there is a tensile force. A straight type overhead lock is placed directly on the support itself, and an oblique type lock can be placed at the support.
If you have decided to use an oblique cut with trimming of the ends, then the bond must be 2.5-3 of the thickness of the bar. In such situations, dowels can also be used.
When fastened with a tension lock of an oblique or straight type, a high level of strength is achieved. But at the same time, such a docking is difficult to manufacture, and the wedges are somewhat weakened when the tree dries out. For these reasons, this fastening method is not suitable for structures that carry high loads.
Splicing closely implies the movement of both ends of the bar to the support and subsequent fastening with staples.
Splicing: a - half-tree, b - oblique cut, c - straight overhead lock, d - oblique overhead lock, d - straight tension lock, e - oblique tension lock, g - end-to-end.
The fastening of logs or beams can be observed during the construction of walls frame houses, at the top or bottom of the harness. The key types of fasteners are: half-tree, corner frying pan, spike type and half-paw.
Docking in half a tree - direct cutting or cutting off 50% of the thickness at the edges of the bars, as well as their subsequent fastening at a right angle.
The half-leg joint is formed by cutting inclined planes at the edges of the bars, as a result of which a tight connection of the bars is obtained. The slope value must be determined by a special formula.
Cutting with a corner frying pan is very similar to cutting with a half-tree method, but differs from it in that with this type of fastening one of the bars loses a little in width.
The connection of the bars at an angle: a - half-tree, b - half-paw, c - spiked, d - angular.
Height connection
The cruciform fastening of the bars is often observed during the construction of bridge structures. With this option, you can use docking half a tree, a third and a quarter, and also a notch of only one of the bars.
Cross-shaped connection of the bars: a - half a tree, b - a third of a tree, c - a quarter of a tree, d - with a notch of one bar.
The method of building boards or bars in height is called fastening materials in height, which is very actively used in the construction of poles or masts.
Extension is divided into the following types:
- Close with a spike of a hidden type.
- Close with a through-type comb.
- Half wood with bolt fastening.
- Half-tree with fastening on clamps.
- Half-wood with steel strip fastening.
- An oblique type cut with fastening on clamps.
- Close with overlays.
- Fastening with bolts.
The length of the joints themselves, as a rule, is equal to 2/3 of the thickness of the joined bars or 2/3 of the diameter of the logs.
Connection of logs during extension: a - end-to-end with a hidden spike, b - end-to-end with a through ridge, c - half-tree with fastening with bolts, d - half-tree with fastening with strip steel, e - half-tree with fastening with clamps, e - oblique cut with fastening with clamps, g - end-to-end with overlays and fastening by bolts.
spike connection
When the bars are fastened by means of spikes, a direct spike is cut on one of them, and an eye or a nest is made on the other. The knitting of beams with a spike method is actively used in the production of such joinery products as doors, windows or transoms. Each fastening is carried out on the basis of glue. It is allowed to use not only one spike, but several. The greater the number of spikes planned to be made, the larger the gluing area will be, respectively.
This type of docking is divided into: corner end type, corner middle type and corner box type.
For corner fastening of the end type, unclosed through spikes (no more than three), spikes with darkness of the through and non-through type, as well as a plug-in dowel are used. Docking angular median type is quite common on the doors. With corner fasteners of the middle and end type, you can additionally use screws, nails or bolts.
Angled middle joints on the spike: a - blind type US-1, b through US-2, c - double through US-3, d - blind into the groove and crest US-4, e - blind into the groove US-5, e - blind on round dowels US-6.
That's all the key information about the existing types of connections. This does not include connections with nails, screws or bolts. Pure wood well and a little bit of glue. 🙂
Joinery bars are interconnected by a spike joint, consisting of two elements - a spike and a socket or eye. Spike - a protrusion at the end of the bar, included in the corresponding
Rice. 42. Types of spikes:
but- single, b- double, in- multiple G- round, d- dovetail e- one-sided dovetail f, h- serrated And- nest, k, l- eyelets, m- deaf thorn n- thorn in the dark, about- spike in
semidarkness
vuyuschie nest or eyelet of another bar. The spikes are single (Fig. 42, a), double (Fig. 42.6), multiple (Fig. 42, c), that is, more than two.
A solid spike is a spike that is integral with the bar. A plug-in spike is a spike made separately from the bar. A spike with a cross section in the form of a circle is called round (Fig. 42, G).
The dovetail spike (Fig. 42.5) has a profile in the form of an isosceles trapezoid with a large base on the end face of the spike, a one-sided dovetail spike - in the form of a rectangular trapezoid with a large base on the end face of the spike (Fig. 42, e).
The toothed spike has a profile in the form of a triangle or trapezoid, the smaller base of which is the end face of the spike (Fig. 42, h), bi-oblique serrated spike (Fig. 42, g) of an isosceles triangle.
Single and double spikes are used in the manufacture of windows, frame doors, furniture; spike "dovetail" - in the manufacture of boxes, boxes; jagged spikes - for glued joining of parts (splicing) along the length.
In addition, round plug-in spikes are used when connecting plots (blanks) in width. Thorns in the dark and semi-darkness (Fig. 42, but), used in the manufacture of frames, me-
Rice. 43. The shape of the processed bars:
but- chamfer, b- headquarters (shtap), in- edge rounding G- fillet, d- fold-quarter, e- kalevka, well- Thorn, h- eye, And- edge with profile processing, to- bar, l - nest, m- layout, n- plastic, about- overhang; / - shoulders, 2 - lateral edge of the spike, 3 - end face of the spike, 4 - panel, 5 - edge, b- butt, 7 - face; / - spike length, b- stud width, s - stud thickness
leucorrhea, etc. In addition, sockets and eyes are used, a deaf spike, shown in fig. 42, i, k, l, m.
A dark spike is made not only at the end connection, but also in cases where it is required that the edges of the nest be invisible, since it is not always possible to obtain even edges of the nest. To hide this defect, a darkness is cut out from the spike, that is, a part of the spike is removed along the width from one or both sides.
In order to form a spike, an eyelet, processed bars, i.e. planed from four sides to the required size, -f- pre-marked.
Structural parts and elements of joinery. Joinery products have the following main structural parts and elements.
Bar- the simplest detail; it happens in different sizes, sections and shapes (Fig. 43). The narrow longitudinal side of the bar is called the edge, and the wide longitudinal side is called the face, the line of intersection of the face with the edge is called the rib. The end transverse side of the bar, formed when trimming at a right angle, is called the end.
In the manufacture of window and door blocks, bars of small sections (vertical, horizontal sash sashes) are
they are made of solid wood, and bars of large sections (boxes) are made glued.
layouts are called bars intended for fastening glass in sashes, doors or panels in door leafs frame structure.
Panels are a rectangular shield made of carpentry, chipboard or fiberboard. The shape of the panels are flat, with beveled edges and with profiled edges. The panel within the doors is installed in a groove, rebate and fastened with layouts or placed on bars and fastened with screws.
folded called a rectangular recess in the bar. If the recess has equal sides of the angle, then it forms a quarter.
Platik- ledge formed to hide the gap; used in cases where fitting the part flush is difficult. The use of platik simplifies the assembly of products. It is used in the manufacture of furniture.
Overhang- protrusion beyond the base. Used in the manufacture of furniture.
Galtelyu called a semicircular recess on the edge or face of the part.
Frame consists of four bars forming a square or rectangle. Separate frames have, in addition, internal mullion bars (frame doors, window sashes with slabs).
The frames are assembled on a spiked joint. Small-sized frames are assembled on a single open through spike or spike with a semi-darkness or darkness. In the manufacture of joinery, mainly rectangular frames are used, very rarely (for unique buildings) - polygonal or round. A window sash, a window leaf, a transom, a box - all these are frames.
All connections in window blocks are made on spikes. The strength of a spiked joint is determined by its dimensions and the area of the bonded surfaces. To increase the strength, the spikes are made double (in the windows).
Shields are made massive (plank) or with voids. Massive shields in order to avoid warping should be assembled from narrow slats (parts) with a width of not more than 1.5 thickness, with the selection of fibers, humidity up to (10 ± 2)%.
When gluing parts in width, the same (sapwood) faces of the joined rails should face in opposite directions, and the edges of the same name should face each other.
Joining rails along the length is allowed if the joints are spaced apart and the distance between them in adjacent rails is at least 150 mm. In panels designed for load-bearing structures, the rails do not join along the length. Wall panels, vestibules, etc. are made from shields.
To avoid warping, shields are made with dowels
Rice. 44. Types of shields:
but- with dowels b- with tips in the groove (tongue) and comb, in- with a glued rail at the end, G- with glued triangular rail, d- with a glued triangular rail, e-
multilayer
(rice. 44, a), with tips (Fig. 44.6), with glued and glued rails (Fig. 44, c, g,e). The dowels in the shields are made flush with the plane or protruding. At least two dowels are placed on each shield. Shields with dowels are designed for doors of temporary buildings, etc.
a) S) in)
Rice. 45. Methods for connecting shields:
but- for a smooth fugue, b- on the rail in- in a quarter G- in a groove and a comb, d- in a groove and a triangular comb, e- in dovetail
Rice. 46. Adhesive joints of bars, boards along the length:
but- end, b- on the "must", in- on a stepped "mustache", G- on a stepped "mustache" with blunting, d- jagged e- vertical gear, w - horizontal gear, h- jagged on the "mustache", And- stepped; c - bevel angle, L- the length of the "mustache" of the spike, t- connection pitch, 6 - bluntness, 5 - gap, IN- thickness, i- spike angle
In addition to boards, multilayer shields are made, glued together from three or five single-layer shields with mutually perpendicular direction of the fibers (Fig. 44, e).
Massive shields are glued onto a smooth fugue (Fig. 45, a), on a rail (Fig. 45.6), in a quarter (Fig. 45, c), in a groove and a crest (Fig. 45, d, e) willow "dovetail" (Fig. 45, e).
Connecting wood parts. Splicing of segments along the length can be end, on the "mustache", serrated, stepped (GOST 17161-79).
End glue connection(Fig. 46, but)- this is an adhesive connection with end surfaces of gluing. Under the end adhesive connection on the "mustache" (Fig. 46.6) is understood the adhesive connection with flat bonding surfaces located at an acute angle to the longitudinal axis of the workpieces. Adhesive connectionon a stepped "mustache"(Fig. 46, c) is a joint in which the bonding surfaces have a protrusion that prevents the workpieces from moving in the longitudinal direction during tension. A connection in which the beveled ends of the workpieces have a bluntness that prevents the displacement of the workpieces in the longitudinal direction during tension and compression is called a connection to a stepped "whisker" with a blunt (Fig. 46, G).
Serrated glue connection(Fig. 46, e)- this is a connection with profiled surfaces in the form of toothed spikes, twirlhot glue joint(Fig. 46, e)- connection with the output of the profile of the spikes on the face of the workpiece. In a horizontal gear connection (Fig. 46, g), the profile of the spikes goes to the edge of the workpiece.
Serrated adhesive connection on the "mustache"(Fig. 46, h)- connection
on the “mustache” with profiled bonding surfaces in the form of jagged spikes.
Step glued joint(Fig. 46, And)- end connection with profiled bonding surfaces in the form of a step, the height of which is equal to half the thickness of the workpiece.
The most durable is adhesive connection on a toothed spike. This type of connection is used for splicing bars of sashes, transoms, window and door frames and other building elements.
Serrated glue connection(see fig. 46, e) are manufactured in accordance with GOST 19414-90. The workpieces to be glued should not differ in moisture content by more than 6 %. Knots larger than 5 mm are not allowed in the workpiece joining area. The roughness parameter of the bonding surfaces of toothed spikes Rmax according to GOST 7016-82 should not exceed 200 microns.
The dimensions of the spiked joints are given in Table. one.
tableI. Stud sizes
Rallying consists in connecting bars, boards, plots along the width of the edge into shields or in layers into blocks. Each workpiece connected to the shield is called plot.
In accordance with GOST 9330-76, the connection along the edge is recommended, depending on the purpose of the products, to be made on a rail, in a quarter, in a rectangular and trapezoidal groove and comb, and on a smooth fugue.
When making connections to the K-1 rail (Fig. 47, a), it should be done at / equal to 20 ... 30 mm 1\ 2...3 mm more; S\ take equal to 0.4 So for wood laths and 0.25 5 0 - for plywood laths. Size S\ should be equal to the nearest dimensions of the slotted disc cutter, i.e. 4, 5, 6, 8, 10, 12, 16 and 20 mm. On the edges, one- and two-sided chamfers are allowed.
For a K-2 type connection along a quarter edge (Fig. 47, b):ho= 0.5 So - 0.5 mm, b is dependent on S 0 :
S 0 , mm I2...15 15...20 20...30 30
b, mm 6 8 10 16
Rice. 47. Connection diagrams of boards (plots) along the edge:
but- along the edge on the rail K-1, b- a quarter along the edge of K-2, in- in a rectangular groove and a crest along the edge of K-3, G- in a trapezoidal groove and a crest along the edge of K-5, d- on a smooth fugue K-6 (along the edge), e- along the edge into a rectangular groove and crest K-4
For connection type K-3 in the groove and tongue (Fig. 47, in) rounding radius G make 1 ... 2 mm, and the size 1\ - 1 ... 2 mm larger than / (Table 2). On the edges, one- and two-sided chamfers are allowed.
Table 2.K-3 connection dimensions, mm
|
S, | ||
Dimensions of connections K-4 (Fig. 47, e) are given in table. 3. Table 3K-4 connection dimensions, mm
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Sa |
b | |||||
The dimensions of the grooves and ridges of the K-5 connection (Fig. 47, d) are determined according to Table. 4.
table4. K-5 connection dimensions, mm
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St |
I | |||
The seam formed when connecting plots is called fugue. Plots from which the shield is glued onto a smooth fugue type K-6 (Fig. 47, e) must have smooth and even edges forming a right angle with the plane (plate) along the entire length. If there are no gaps when connecting the plots, then their jointing (fitting) is done with high quality. Shields are glued together in clamps, wai-maxes, presses.
In addition to gluing, shields can be assembled from plots into round plug-in spikes, while the diameter of the spike should be 0.5 of the thickness of the plot, and the length should be 8 ... 10 diameters. The spikes are set in increments of 100 ... 150 mm.
The connection into a groove and a ridge, as well as into a quarter, is made by selecting along the entire length of the edge (plot) on one side of the groove or a quarter, and on the other, a ridge or a quarter. This compound is used in the manufacture of shields, laying plank floors, carpentry partitions, filing ceilings. A plain joint is more economical than a quarter or tongue and groove joint.
When connecting to a rail along the edges of the plots, grooves are selected into which wooden or plywood rails are inserted.
In addition to processing solid pieces of wood, it is often necessary to connect wooden parts into knots and structures. Element connections wooden structures are called landings. Joints in the construction of wooden parts are defined by five types of fits: tense, tight, sliding, loose and very loose fit.
Knots - these are parts of structures at the junction of parts. Connections of wooden structures are divided into types: end, side, corner T-shaped, cross-shaped, corner L-shaped and box corner connections.
Joiner connections have more than 200 options. Only connections used in practice by joiners and carpenters are considered here.
End connection (building) - the connection of parts along the length, when one element is a continuation of another. Such joints are smooth, jagged with spikes. Additionally, they are fixed with glue, screws, overlays. Horizontal end connections withstand compressive, tensile and bending loads (fig. 1 - 5). Lumber is increased in length, forming vertical and horizontal jagged joints (wedge lock) at the ends (Fig. 6). Such joints do not need to be under pressure during the entire bonding process, since significant frictional forces act here. Gear joints of sawn timber, made by milling, meet the first class of accuracy.
Joints of wooden structures must be made carefully, in accordance with the three accuracy classes. The first class is for measuring tool High Quality, the second class - for furniture production, and the third - for building parts, agricultural implements and containers. The lateral connection of several boards or battens with an edge is called rallying (Fig. 7). Such connections are used in the construction of floors, gates, carpentry doors, etc. Plank, rack panels are additionally reinforced with crossbars and tips. When sheathing ceilings, walls, the upper boards overlap the lower ones by 1/5 - 1/4 of the width. The outer walls are sheathed with horizontally laid overlapping boards (Fig. 7, g). The upper board overlaps the lower one by 1/5 - 1/4 of the width, which ensures the removal of atmospheric precipitation. The connection of the end of the part with the middle part of the other forms a T-shaped connection of the parts. Such compounds have a large number of variants, two of which are shown in Fig. 8. These connections (knitting) are used when pairing the log of ceilings and partitions with the harness of the house. The connection of parts at a right or oblique angle is called a cruciform connection. Such a connection has one or two grooves (Fig. 3.9). Cross-shaped connections are used in the construction of roofs and trusses.
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| Rice. 1. End connections of the bars, resisting compression: a - with a straight half-wood overlay; b - with an oblique overlay (on the "mustache"); c - with a straight half-wood overlay with a joint in an obtuse angle; g - with an oblique overlay with a joint into a spike. |
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| Rice. 2. End connections of the bars (extension), resisting stretching: a - in a straight overhead lock; b - in an oblique laid on lock; c - with a straight overlay half a tree with a joint in an oblique spike (in a dovetail). |
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| Rice. 3. End connections of beams that resist bending: a - with a straight half-wood overlay with an oblique joint; b - with a straight overlay half a tree with a stepped joint; in - in an oblique laid on lock with wedges and with a joint in a thorn. |
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| Rice. 4. Splicing with a notch reinforced with wedges and bolts. |
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| Rice. 5. End connections of the bars, working in compression: a - end-to-end with a hidden hollowed-out spike; b - end-to-end with a hidden plug-in spike; c - with a straight overlay half a tree (the connection can be reinforced with bolts); mr. straight half-wood overlay with wire fastening; e - with a straight overlay half a tree with fastening with metal clips (clamps); e - with an oblique overlay (on the "mustache") with fastening with metal clips; g - with an oblique overlay and fastening with bolts; h - marking the oblique lining; and - end-to-end with a secret tetrahedral spike. |
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| Rice. Fig. 6. End extensions of the milling scheme for end gluing of workpieces: a - vertical (along the width of the part), toothed (wedge-shaped) connection; b - horizontal (through the thickness of the part), gear (wedge-shaped) connection; c - gear joint milling; g - sawing out a gear connection; e - milling of a gear connection; e - end connection and gluing. |
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| Rice. 7. Rallying boards: a - for a smooth fugue; b - on the plug-in rail; in - in a quarter; d, e, f - into a groove and a crest (with various forms of a groove and a crest); g - overlap; h - with a tip in the groove; and - with a tip in a quarter; to - with overlap. |
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| Rice. 8. T-shaped joints of bars: a - with a hidden oblique spike (in a paw or in a dovetail); b - with a straight stepped overlay. |
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| Rice. 9. Cross connections of bars: a - with a straight overlay half a tree; b - with a direct overlay of incomplete overlap; c - with landing in one nest |
The connections of two parts with ends at a right angle are called angular. They have through and non-through spikes, open and in the dark, half-dark overlay, half-tree, etc. (Fig. 10).
Corner joints (knitting) are used in window irregular blocks, in greenhouse frame joints, etc. A spike connection in the dark has a spike length of at least half the width of the connected part, and the groove depth is 2–3 mm more than the spike length. This is necessary so that the parts to be joined easily mate with each other, and after gluing, there is room for excess glue in the spike socket. For door frames apply angular tenon connection in the dark, and to increase the size of the connected surface - in a semi-darkness. A double or triple tenon increases the strength of the gusset. However, the strength of the connection is determined by the quality of its execution. IN furniture production a variety of corner box connections are widely used (Fig. 11). Of these, the simplest is an open end-to-end spike connection. Before making such a connection, spikes are marked with an awl at one end of the board according to the drawing. By marking the side parts of the spike with a file with fine teeth, a cut is made. Every second cut of the spike is hollowed out with a chisel. For the accuracy of the connection, they first saw through and gouge out the sockets for the spikes in one piece. It is applied to the end of another part and crushed. Then they saw through, gouge and connect the parts, cleaning the connection with a planer, as shown in fig. eleven.When connecting the parts to the "mustache" (at an angle of 45 °), the angular knitting is fixed with steel inserts, as shown in fig. 12. At the same time, make sure that one half of the insert or clamp is included in one part, and the other half is in the other. A wedge-shaped steel plate or ring is placed in the milled grooves of the parts to be joined.
The corners of frames and boxes are connected with a direct open through spike connection (Fig. 3.13, a, b, c). With increased quality requirements (the spikes are not visible from the outside), the corner knitting is performed by an oblique blind connection, a groove and a ridge, or an oblique connection to the rail, as shown in fig. 13, d, e, f, g and in fig. fourteen.
A box structure with horizontal or vertical transverse elements (shelves, partitions) is connected using corner T-shaped joints shown in fig. 15.
In connecting the elements of the upper belt of wooden trusses with the lower one, corner cuts are used. When mating the truss elements at an angle of 45 ° or less, one cut is made in the lower element (puff) (Fig. 16, a), at an angle of more than 45 ° - two cuts (Fig. 16.6). In both cases, the end cut (cut) is perpendicular to the direction of the acting forces.
Additionally, the nodes are fixed with a bolt with a washer and a nut, less often with brackets. The log walls of the house (log house) from horizontally laid logs in the corners are connected with a cut “in the paw”. It can be simple or with an additional spike (shank with a pit). The marking of the cut is performed as follows: the end of the log is hewn into a square, to the length of the side of the square (along the log), so that after processing a cube is obtained. The sides of the cube are divided into 8 equal parts. Then, 4/8 part is removed from one side from below and from above, and the remaining sides are performed, as shown in Fig. 17. Templates are used to speed up the marking and the accuracy of making cuts.
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| Rice. 10. Corner end connections of blanks at a right angle: a - with a single opening through a spike; b - with a single through hidden spike (in the dark); in-with a single deaf (non-through) thorn in the dark; g - with a single through semi-secret spike (in semi-darkness); d - with a single deaf spike in semi-darkness; e - with a triple open through spike; g - in a straight overlay half a tree; h - in a through dovetail; and - in eyelets with undercutting. |
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| Rice. 11. Box corner joints with straight through spikes: a - sawing tenon grooves; b - marking the spikes with an awl; in - connection of a thorn with a groove; g - processing by a planer of a corner joint. |
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| Rice. 12. Corner end connections at a right angle, reinforced with metal inserts - buttons: a - 8-shaped insert; b- wedge-shaped plate; in rings. |
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| Rice. 13. Box corner joints at a right angle: a - straight open through spikes; b - oblique open through spikes; in - open through dovetail spikes; g - groove on the plug-in rail end-to-end; d - in the groove and crest; e - on plug-in spikes; g - on spikes in a dovetail in semi-darkness. |
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| Rice. 14. Oblique (on the "mustache") box connections at a right angle: a - oblique spikes in the dark; b - oblique connection on a plug-in rail; in - oblique connection on spikes in the dark; g - an oblique connection, reinforced with a trihedral rail on glue. |
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| Rice. 15. Direct and oblique connections of blanks: a - on a double connection in an oblique groove and ridge; b - on a straight groove and comb; in - on a trihedral groove and a crest; g - on a straight groove and a comb in the dark; d - on straight through spikes; e - on round plug-in spikes in the dark; g - on a spike in a dovetail; h - on the groove and the crest, reinforced with nails. |
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| Rice. 16. Nodes in farm elements. |
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| Rice. 17. Conjugation of the logs of the walls of the log house: a - a simple paw; b - a paw with a wind spike; c - paw markings; 1 - wind spike (pit) |
The rafter system is the most complex and one of the most critical elements of the house; the comfort and operating time of the building largely depend on the correctness of its construction. Calculation and design truss system should only be done experienced builders or engineers with special training.
Designing a wooden truss system is much more difficult than any metal constructions. Why? In nature, there are no two boards with exactly the same strength indicators, this parameter is influenced by a lot of factors.
The metal has the same properties, which depend only on the steel grade. The calculations will be accurate, the error is minimal. With a tree, everything is much more complicated. In order to minimize the risks of destruction of the system, it is necessary to give a large margin of safety. Most decisions are made directly by the builders on site after assessing the condition of the lumber and taking into account the design features. Practical experience is very important.
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Building boards
Why you need to splice rafters
There are several reasons why splicing rafters is required.
- Roof length exceeds standard lumber length. The standard length of the boards does not exceed six meters. If the slope is large, then the boards will have to be lengthened.
- During construction, there are many good boards 3–4 m long. To lower the estimated cost of the building and reduce the amount of non-productive waste, these pieces can be used for the manufacture of rafters, having previously spliced them.
Important. It must be remembered that the strength of spliced rafters is always lower than that of whole ones. It is necessary to try to ensure that the splicing point is located as close as possible to the vertical stops.
Splicing methods
There are several ways to splice, there is definitely no better or worse. Masters make decisions based on their skills and the specific location of the joint.
Table. Methods for splicing rafters.
| splicing method | Brief description of technology |
|---|---|
| It is used on boards with a thickness of at least 35 mm. Enough complicated method requires hands-on carpentry experience. In terms of strength, the connection is the weakest of all existing ones. Advantage - saving lumber. Practically at construction sites it is used very rarely. |
| The length of the rafter legs is increased with the help of an overlay. The lining can be wooden or metal. If the length of the two segments of the boards is insufficient in terms of the parameters of the truss system, then this method allows them to be increased. Butt joint has the highest bending strength, is widely used during the construction of various structures. |
| Overlap. Two boards are fixed with an overlap. The simplest method, in terms of strength, occupies a middle position. The disadvantage is that the total length of the two boards must be greater than the design length of the rafter leg. |
In this article, we will look at two of the simplest and most reliable splicing methods: butt and overlap. It makes no sense to touch the oblique cut, it is almost never used due to a large number shortcomings.
Requirements of building codes and rules for splicing rafters
Inept splicing of rafters along the length can not only dramatically reduce their resistance to bending loads, but also cause complete destruction of the structure. The consequences of this situation are very sad. Building rules provide for certain patterns during the selection of fastener sizes, installation locations and the length of the overlays. The data are taken taking into account many years of practical experience.
Spliced rafters will be much stronger if metal studs rather than nails are used to connect them. The instruction will help to make an independent calculation of the connection. The advantage of the method is its versatility, it can be used to solve problems not only with lengthening the rafters, but also with building up other roof elements. Specialized companies performed rough calculations and collected data in a table, but it only indicates the minimum acceptable parameters.
- Stud diameter and length. In all cases, the diameter of the studs must be ≥ 8 mm. Thinner ones do not have sufficient strength, it is not recommended to use them. Why? IN metal connections the diameter of the studs is calculated for tensile forces. During contraction metal surfaces pressed against each other so strongly that they are held by friction. In wooden structures, the stud works in bending. Separate boards cannot be pulled together with great effort, the washers fall into the board. In addition, during changes in relative humidity, the boards change thickness, thereby reducing the tightening force. Studs working in bending must be large. The specific diameter of the stud must be determined by the formula dw = 0.25×S, where S is the thickness of the board. For example, for a board with a thickness of 40 mm, the diameter of the stud should be 10 mm. Although this is all rather relative, you need to keep in mind the specific loads, and they depend on many factors.
- Board overlap length. This parameter should always be four times the width of the boards. If the width of the rafters is 30 cm, then the length of the overlap cannot be less than 1.2 m. We have already mentioned that the specific decision is made by the master, taking into account the condition of the lumber, the angle of the rafters, the distance between them, the weight roofing materials and climatic zone of the building location. All these parameters have a great influence on the stability of the truss system.
- Distance between stud holes. Fasteners are recommended to be fixed at a distance of at least seven diameters of the studs, from the edge of the board the distance should be at least three diameters. These are the minimum figures, in practice it is recommended to increase them. But it all depends on the width of the board. It is impossible to reduce the distance between the rows of studs too much by increasing the distance from the edge.
- Number of tie rods. There are quite complex formulas, but in practice they are not used. Masters install two rows of studs, taking into account the distance between them, the holes are staggered.
Practical advice. To increase the bending strength of the spliced rafter, the holes of the studs should not be located on the same line, they must be displaced by at least one diameter.
Splicing butt boards
Work is much more convenient to do on the ground, prepare a flat area. Put the bars on the ground - the rafters will have to be cut, you need a clearance for a circular saw. Before splicing, find out exactly the length of the rafters. You need to measure it on the building, use any thin long boards, rope or construction tape. If there is an error of a few centimeters - not a problem. During the connection of the rafter legs on the roof, this error is eliminated without problems.
Step 1. Lay one board on the bars, cut the end exactly at a right angle. It is better to cut off with a manual electric circular saw.
Important. Follow the safety rules, this is a high-speed and very traumatic tool. Never dismantle the factory protective devices of the saw blade, do not turn off the electrical overload relays.
The rafter boards are quite heavy, while cutting, give them such a position that they do not pinch the saw blade or break prematurely during recutting. Prepare the second board in the same way. Make sure that the cut is only at a right angle. The ends of the spliced boards should fit snugly against each other over the entire surface, this is necessary to increase the strength of the spliced rafters. The fact is that even with the weakening of the connection of the studs, the ends during bending will rest against each other along the entire length of the cut and hold the load. Studs and overhead boards will only keep the structure from spreading along the length.
Step 2 Place two prepared rafter boards side by side. Prepare the board for the overlay. We have already mentioned that its length should be about four times the width of the board. If the roof slopes have a slight slope, the distance between the rafters is large, and the roof will be insulated mineral wool, then the bending loads increase significantly. Accordingly, the length of the splicing board must be increased.
Step 3 Lay the overlay on two side by side splicing boards. Quite often, the thickness and width of the boards, even from the same batch, differ by several millimeters. If you have such a case, then level the boards on the side to which the crate will be nailed.
Practical advice. The science of the strength of materials says that the thinner the material, the greater its resistance to bending along a thin plane. This means that, for example, five boards placed side by side on an edge with a thickness of 1 cm each withstand a significantly greater load than one board 5 cm thick. Conclusion - it is not necessary to cut thick expensive materials for splicing, you can use several thin pieces of the desired length. There are enough such pieces at any construction site.
Step 4 In a checkerboard pattern and at standardized distances, drill holes for the studs. In order to prevent the individual elements from moving during drilling, they must be temporarily fixed together. Use long and thin self-tapping screws for this purpose; it is not recommended to hammer with nails. They cut or tear the fibers of the wood, the strength of the board is slightly reduced. Self-tapping screws do not cut the fibers, but push them apart, after unscrewing the boards, they almost completely restore their original strength characteristics.
Step 5 Drill holes, do not place them in one line, otherwise the boards may crack during operation.
You can find recommendations after drilling holes to separate the boards and lay jute between them to prevent the appearance of cold bridges. This is not only vain work, but also harmful. Why? Firstly, no cold bridges appear at the splicing points; on the contrary, they have the largest thickness and, accordingly, the lowest thermal conductivity. But even if they appear, there will be no negative consequences, this is a roof truss system, and not room window or a door. Secondly, jute reduces the friction force between the splicing elements, and this has a very negative effect on their strength. Thirdly, if condensate gets on the material, which is very likely, then moisture will be removed from it for a very long time. There is no need to tell what consequences the prolonged contact of wooden structures with moisture leads to.
Step 6 Insert the studs into the prepared holes, put washers on both sides and tighten them firmly with nuts. It is recommended to tighten until the washers are pressed into the tree. The excess length of the studs can be cut off with a circular grinder with a metal disc.
All other rafters are spliced in the same way.
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Electric drills
Overlap splicing
This connection is easier to make, but under one condition - the total length of the two boards allows, it must be greater than the length of the rafter leg by the amount of overlap.
If you have low quality lumber, then before starting work it is recommended to decompose them into flat surface and make a revision. For long sections of spliced rafters, choose straight ones, and for segments, use curves. Although it is strongly recommended to buy only high-quality materials for the truss system, this is not the architectural element of the building that you can save on.
Step 1. Select boards and place them on top of the raised beams. If you wish, you can align the ends with circular saw, there is no desire - do not equalize. The condition of the ends does not affect the strength of the overlap splicing.
Step 2 Lay the boards on top of each other, adjust the length of the joint and overall size rafters.
Practical advice. Boards should lie on top of each other strictly parallel. Due to the fact that the upper one rises above the lower one by the thickness of the material, it is necessary to place stands from segments under it and the bars. The thickness of the segments should be equal to the thickness of the bottom board.
Step 3 Align the boards on one of the edges and temporarily fasten them with self-tapping screws. Drill holes, install studs, washers and tighten nuts.
Butt splicing with plywood
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Clamps
One of the ways to splice rafters helps to save boards and rationally use the waste of various lumber. In this case, cut plywood sheets with a thickness of one centimeter are used.
Step 1. Lay the rafter boards evenly on the site, close the ends, pay attention to the parallelism of the side faces. The boards must be extremely uniform in thickness, the ends are cut exactly at a right angle.
Step 2 With a brush, generously smear the surface with PVA glue.
Step 3 Lay the prepared piece of plywood on the splicing site, press it firmly with clamps. During fixing, make sure that the plywood does not move from its original place.
Step 4 Fasten the plywood to the boards with long, strong self-tapping screws in a checkerboard pattern. The length of the self-tapping screws should be 1–2 shorter than the total thickness of the boards and plywood, their ends cannot come out from the back. Be sure to put washers under the screws large diameter. Before tightening the screws, drill holes in the rafter. Their diameter should be 2–3 mm less than the diameter of the threaded part of the hardware.
Step 5 Turn the board upside down, put it under the ends of the stand, they should not hang in the air. Carefully remove all installed clamps one by one.
Step 6 Spread the surfaces with glue and place a second piece of plywood on them. Clamp it again with clamps.
Step 7 Tighten the screws with great force.
Important. When tightening the screws, pay attention that they are not located against each other. The offset must be at least three centimeters.
Step 8 Remove clamps. To strengthen the splice knot, tighten it with through pins. They should be placed in the same way as with ordinary butt splicing.
Practical advice. Holes for studs should be 0.5–1.0 mm smaller than the diameter of the stud. There are times when it is impossible to accurately select the diameter of a drill for wood. Then it is recommended to use a slightly smaller diameter drill, let the stud come in with a sufficiently large effort.
During its clogging from strong blows of the hammer, the first few turns of the thread are crushed, which makes it very difficult to wind the nut. To avoid problems, start the nuts before driving the stud, now let the thread on the end be jammed, it is no longer needed. Before installing the rafter in place, check that the glue has dried. In good weather, it takes about 24 hours for it to solidify completely.
The final touch - applying glue
Important. If, during the splicing of the rafters along the length of the boards, the nuts were twisted until the washer was sunk into the wood, then this cannot be done with plywood. Carefully control the pressing force, do not damage the plywood veneer.
How to properly hammer nails into the rafter when splicing
It is not always possible and necessary to splice individual elements of the rafters with the help of studs, sometimes it is easier to do this with ordinary smooth nails. But you need to be able to score them correctly, otherwise, over time, the compression force of the boards will decrease significantly. The length of the nail should be 2.5–3 cm greater than the thickness of the rafter at the junction.
How to properly drive in nails to connect loaded or critical wooden structures?
Step 1. At a slight angle, drive the nail into the boards, but not all the way. It is necessary that the tip protrudes from the back side by about one centimeter.
Step 2 On the reverse side of the rafter, bend the nail at a right angle with a hammer.
Step 3 Drive the nail in about one centimeter more. Bend the end again, the bend angle should already be much less than 90°. The more you bend it, the more secure the final fixation will be.
Step 4 Now you can drive the nail head to the very end. On the reverse side, bend the protruding part until the sharp end fully enters the board. Remember that the exit point of the nail body and the place where its point is driven in should not lie on the same line.
This technology completely eliminates the independent weakening of the pressing force.
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Fasteners for rafters
It has already been mentioned that the bending strength of the rafter at the splicing point is always less than that of the whole element. If possible try to place this knot as close as possible to the ridge, mauerlat or various spacers. Such precautions minimize the risks of mechanical destruction of the rafter leg. If this is not possible for one reason or another, then it is not recommended to place the stop under the splice at a distance of more than 15% of the leg length from either end.
Never use black screws to connect. This metal has two significant drawbacks. First, it quickly oxidizes and loses its original strength. The second - the manufacturing technology of such self-tapping screws involves hardening. Hardened self-tapping screws, when the permissible load is exceeded, do not stretch, but burst. During the operation of the roof, the relative humidity of wooden structures changes, and the thickness of the boards fluctuates accordingly. And this can significantly increase the tensile force of the self-tapping screw, it will not withstand and will crack.
Do not overdo it with the number of hardware. If there are too many of them, then the holes will significantly reduce the strength of the parts to be joined, as a result you will get the opposite effect, the build-up will not increase, but weaken.
Video - Splicing rafters along the length
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