Wooden parts are used in many products. And their connection is an important process on which the strength of the entire structure depends.
Dozens of wood products are used to make furniture and other wood products. various connections. The choice of method for connecting wooden parts depends on what the product should be like in the end and what load it should bear.
Types of connection
When connecting wooden parts you need to remember important point- a thin part is always attached to a thick one, but not vice versa.
According to the relative arrangement of the elements, the following methods of connecting wooden parts are distinguished:
- extension - increasing the height of a part;
- splicing - elongation of the workpiece;
- rallying - increasing the width of an element;
- knitting - joining at an angle.
The most commonly used methods for joining wooden parts in furniture making are:
- gluing;
- "dovetail";
- end-to-end;
- grooved;
- overlap;
- deaf on spikes;
- through tenon.
Let's look at the technologies of some connections in more detail.
Length splicing
Such wooden parts have some nuances. At its core, this is the elongation of elements in the horizontal direction. Splicing can be:
- Butt-end - the ends are cut at right angles and aligned with each other. A bracket is hammered into both beams (logs).
- Oblique butt - the cuts are made at an angle, and the ends are fastened with a pin or nail.
- End butt with ridge.
- Direct overlay - the length of the cutting is 1.5-2 times greater than the thickness of the timber (log).
- Oblique overlay - the ends are cut at an angle and fixed with bolts.
- Overlay with an oblique cut - at the ends of the parts, end ridges are made, having a width and length of one third of the thickness of the beam.
Increase in height
From the name it is clear that the essence is to lengthen the beams or logs in the vertical direction. The axes of the elements are on the same vertical line. Types of extensions are:
- End-to-end extension. To absorb random loads, a barbed pin is inserted on the sides.
- Extension with one or two spikes. The width and height of one tenon must be at least one third of the thickness of the timber. The depth of the nest is slightly greater than the height of the spike.
- Half-tree extension. The ends of both logs need to be cut to half their thickness by 3-3.5 diameters in length.
- Tongue building. In one beam you need to cut a fork into which you need to insert the correspondingly cut end of another piece. The connection itself must be wrapped in tin.
Width joining
Used to increase the width of the product. When using bonding methods, it is important to pay attention to the location of the tree’s annual rings. It is important to alternate the boards depending on their direction. The payment options are:
- Butt-to-end - the parts need to be trimmed and jointed using a square.
- In tongue and groove - the height and width of the ridge is equal to 1/3 of the thickness of the board.
- Using a hacksaw, the edges must be cut at an acute angle to the wide plane of the board.
- With a comb with a height of 1/3 to half of the board.
- A quarter with a ledge equal to half the thickness of the board.
- In tongue and groove with slats - in each board, select grooves into which you need to insert a rake that is twice as wide as the depth of the groove.
Mating
Knitting is used when there is a need to connect parts at an angle. Types of knitting are:
- half-tree knitting using a hidden spike;
- half-paw mating;
- single and double slotted tenons;
- slotted paw.
to the end
The easiest way to join two parts together. Joining wooden parts at right angles is done using this method. The surfaces of the two parts are carefully adjusted to each other and pressed tightly. The wooden parts are connected with nails or screws. Their length should be such as to pass through the first part and go deeper into the second by about 1/3 of the length.
In order for the fastening to be reliable, it is necessary to drive in at least two nails. They need to be located on the sides of the center line. The thickness of the nail should not cause cracking of the wood. Therefore, it is recommended to make holes in advance with a diameter of 0.7 of the thickness of the nail used.
To enhance fixation, lubricate the surfaces that are connected with glue. For rooms that will not be exposed to moisture, you can use carpentry, casein or hide glue. If the product is used in conditions high humidity It is better to use moisture-resistant glue, for example, epoxy.
T-shaped connection with overlay
To make such a connection of wooden parts, you need to place one piece on top of another and fasten them to each other using bolts, screws or nails. Wooden blanks can be placed either at a certain angle to each other or along one line.
To ensure that parts do not change, use at least 4 nails. If there are only two nails, then they are driven in diagonally. To make the fixation more durable, the nails must pass through both parts, and the protruding ends must be bent and deepened into the wood.
Half-tree connection
To perform such a connection between two wooden parts, certain skills and experience are required. It is performed as follows. In both workpieces, samples are made with a depth that corresponds to half their thickness. The width of the selection must be equal to the width of the part.
The method of joining wooden parts into half a tree can be done at different angles. In this case, it is important to ensure that the angle is the same on both wooden blanks, and the width corresponded to the width of the part. Thanks to this, the parts are pressed tightly against each other, and their edges are located in the same plane.
In addition, such a connection can be complete or partial. In the case of a partial connection, the end of one workpiece is cut at a certain angle, and a corresponding cut is made at the end of the other. Such joints include angular half-tree joints. The idea is to trim both tenons at an angle of 45 degrees, as a result of which the seam between them is located diagonally. When using this method, you need to be especially careful, and make corner cuts with a special tool - a miter box.
Cleat
Such wooden parts are used for fastening sheathing boards or when laying floors. The edge of one board has a tenon, and the edge of the other has a groove. Accordingly, fastening occurs when the tenon enters the groove. This connection looks very neat, since there are no gaps between the boards.
Doing tenons and mortises requires some experience. And besides, for production you will need a special machine. Therefore, it is easier to purchase ready-made parts.
Connection "socket-spike"
The most commonly used method of joining wooden parts. This joint is strong, rigid and looks as neat as possible. To make such a connection, you need to have some skills and experience, as well as be careful. An incorrectly made socket-tenon connection is fragile and looks unsightly.
Its essence is as follows. At the end of one workpiece a groove is drilled or gouged out, and at the end of the other - a tenon. It is better when the elements have the same width. If the thickness is different, then the tenon is made in a thin part, and the groove, accordingly, in a thick one.
Subsequence finger joint:
- Using a thicknesser, draw two marks parallel to each other on the side of one workpiece. The distance should be the width of the future spike. To ensure its evenness, markings should be made on both sides.
- Most optimal tool for making tenons - a hacksaw with a narrow blade and fine teeth, or bow saw. During operation, the teeth of the tool must pass along the inner edge marking line. For convenience, it is better to clamp the part in a vice. It is best to make the spike slightly larger than the required size. Then, if necessary, you can remove the excess. But if the spike turns out to be shorter, then the whole process will need to be repeated again.
- Using a chisel or chisel, a socket (groove) is made in the second part. Naturally, the dimensions of the groove must correspond to the dimensions of the tenon. It is best to drill holes around the entire perimeter of the groove before starting chiselling. The edges are carefully processed with a chisel.
If the connection of wooden parts is done correctly, then the surfaces of the edges of the tenons fit tightly to the walls of the nest. This gives good adhesion when gluing. To make the pins fit tighter, their dimensions should be 0.2-0.3 mm larger than the dimensions of the socket. If this value is exceeded, the bowstring may split; if the tolerance is less, the fastening will lose its strength during operation.
In addition, such a connection also involves gluing and fastening with screws, nails or wooden dowels. To simplify the work, you should drill holes before screwing in the screws. The screw heads are hidden in a countersunk (made using a countersink). The pilot hole should be equal to 2/3 of the diameter of the screw and 6 mm (approximately) less than its length.
Gluing
Gluing wooden parts is carried out as follows:
- The surfaces to be glued are cleaned with a lint-free cloth, and rough spots are smoothed out with fine sandpaper.
- Using a cardboard stick, apply wood glue evenly. thin layer on all necessary surfaces.
- Surfaces coated with glue should be rubbed against each other. This will ensure even contact and strong adhesion.
- The parts need to be pulled together to ensure reliable retention at the joints. Measuring the diagonals will make sure the angles are straight. They must be equal. If this is not the case, the position of the elements needs to be corrected.
- The connection is strengthened by drilling pilot holes into which finishing nails or screws are driven. The screw heads must be recessed; for this, the holes must be bored out. The nails are deepened using a punch.
- Holes with nails are covered with wood putty. The holes bored out for the screws are closed with hardwood wooden plugs coated with glue. When the glue or putty has dried, the surface is sanded so that it is smooth and then varnished.
Necessary tools and equipment
The tools for execution are very diverse. They are selected depending on the type of work performed. Since in carpentry the elements being processed are larger than in carpentry, therefore, the tool must be suitable.
To connect wooden parts use the following:
- axe;
- plane, straight and curved planes, bear, sherhebel - more thorough surface treatment;
- chisel - chiseling holes and sockets;
- chisel - for cleaning cuts;
- drills with different tips - for through holes;
- various saws - for sawing lengthwise and crosswise;
- hammer, hammer, sledgehammer, mallet;
- square, compass, level and others auxiliary tools;
- nails, metal staples, bolts with nuts, screws and other fastening products.
Conclusion
In fact, there are many more ways to connect wooden parts of furniture or other structures. The article describes the most popular methods and technologies of implementation. It is important to remember that the connection of wooden parts for painting or varnishing must be carefully prepared, and all fastenings must be strong and made conscientiously.
Often during the construction of roof frames with complex configurations, the need arises to use elements of non-standard sizes. Typical examples include hip and half-hip structures, the diagonal ribs of which are significantly longer than ordinary rafter legs.
Similar situations arise when constructing systems with valleys. To ensure that the created connections do not cause weakening of structures, you need to know how rafters are spliced along the length and how their strength is ensured.
Splicing the rafter legs allows you to unify the lumber purchased for constructing the roof. Knowledge of the intricacies of the process makes it possible to almost completely construct a rafter frame from a bar or board of the same section. The design of the system from materials of the same size has a beneficial effect on the total cost.
In addition, boards and bars of increased length, as a rule, are produced with a cross-section larger than that of the material standard sizes. Along with the cross-section, the cost also increases. Such a safety factor when installing hip and valley ribs is most often not needed. But if the rafter splicing is carried out correctly, the elements of the system are provided with sufficient rigidity and reliability at the lowest cost.
Without knowledge technological nuances It is quite difficult to make truly bending-rigid lumber joints. The connecting nodes of the rafters belong to the category of plastic hinges, which have only one degree of freedom - the ability to rotate in the connecting node when a vertical and compressive load along the length is applied.
In order to ensure uniform rigidity when bending force is applied along the entire length of the element, the junction of the two parts of the rafter leg is located in places with the lowest bending moment. In diagrams demonstrating the magnitude of the bending moment, they are clearly visible. These are the points of intersection of the curve with the longitudinal axis of the rafters, at which the bending moment approaches zero values.
Let us take into account that when constructing a rafter frame, it is necessary to ensure equal resistance to bending along the entire length of the element, and not equal opportunities to bend. Therefore, the interface points are located next to the supports.
Both the intermediate post installed in the span and the Mauerlat or truss truss itself are used as support. The ridge girder can also be assessed as a possible support, but the joining areas of the rafter legs are better located lower along the slope, i.e. where minimal load is placed on the system.
Options for splicing rafters
Except precise definition where to connect the two parts of the system element, you need to know how the rafters are extended correctly. The method of forming the connection depends on the lumber chosen for construction:
- Bars or log. They are built up with an oblique cut formed in the joint area. To strengthen and to prevent rotation, the edges of both parts of the rafters, cut at an angle, are fastened with a bolt.
- Boards sewn together in pairs. They are spliced with the arrangement of joining lines staggered. The connection of two overlapping parts is made with nails.
- Single board. The priority is splicing with a frontal stop - by joining the trimmed parts of the rafter leg with the application of one or a pair of wooden or metal overlays. Less commonly, due to the insufficient thickness of the material, an oblique cut with fastening with metal clamps or traditional nailing is used.
Let us consider these methods in detail in order to understand in depth the process of increasing the length of the rafters.
Option 1: Oblique cut method
The method involves the formation of two inclined notches or cuts arranged on the side where the parts of the rafter leg meet. The planes of the notches to be joined must be perfectly aligned without the slightest gap, regardless of their size. The possibility of deformation must be excluded in the connection area.
It is prohibited to fill cracks and leaks with wedges made of wood, plywood or metal plates. It will not be possible to adjust and correct flaws. It is better to accurately measure and draw cutting lines in advance, according to the following standards:
- The depth is determined by the formula 0.15 × h, where h denotes the height of the beam. This is the size of the area perpendicular to the longitudinal axis of the beam.
- The interval within which the sloping areas cutting, is determined by the formula 2 × h.
The location for the joining section is found using the formula 0.15 × L, valid for all types of rafter frames, in which the value of L reflects the size of the span covered by the rafters. The distance is measured from the center of the support.
Parts made of timber when making an oblique cut are additionally secured with a bolt passing through the center of the connection. The hole for its installation is drilled in advance; its Ø is equal to the Ø of the fastener rod. To prevent the wood from being crushed at the mounting location, wide metal washers are placed under the nuts.
If a board is connected using an oblique cut, then additional fixation made using clamps or nails.
Option 2: Placing the boards together
When using bonding technology, the center of the connected area is located directly above the support. The joining lines of the trimmed boards are located on both sides of the center of the support at a calculated distance of 0.21 × L, where L denotes the length of the overlapped span. Fixation is carried out with nails installed in a checkerboard pattern.
Backlash and gaps are also unacceptable, but they are easier to avoid by carefully trimming the board. This method is much simpler to implement than the previous method, but in order not to waste hardware and not weaken the wood with unnecessary holes, you should accurately calculate the number of fastener points to be installed.
Nails with a stem cross-section up to 6 mm are installed without preliminary drilling of the corresponding holes. It is necessary to drill for fasteners larger than the specified size so as not to split the board along the fibers when connecting. The exception is hardware with a cross-section, which, regardless of size, wooden parts you can just score.
To ensure sufficient strength in the bonding zone, the following conditions must be met:
- Fasteners are placed every 50 cm along both edges of the boards being joined.
- Along the end connections, nails are placed in increments of 15 × d, where d is the diameter of the nail.
- Smooth round, screw and threaded nails are suitable for holding the board together at the joint. However, threaded and screw options are a priority, because their pull-out strength is much higher.
Note that connecting rafters by welding is acceptable if an element is constructed from two sewn boards. As a result, both joints are covered with a solid section of lumber. The advantages of this method include the size of the overlapped span, which is impressive for private construction. In a similar way, you can extend the rafter legs if the distance from the top to the bottom support reaches 6.5 m.
Option 3: Frontal rest
The method of frontal extension of rafters consists in the end joining of the connected parts of the rafter leg with fixation of the section with nails, dowels or bolts through linings installed on both side planes.
To avoid play and deformation of the extended rafter leg, you must adhere to the following rules:
- The edges of the boards to be joined must be perfectly trimmed. Gaps of any size along the connection line must be eliminated.
- The length of the pads is determined by the formula l = 3 × h, i.e. they must be no less than three times the width of the board. Usually the length is calculated and selected based on the number of nails; the formula is given to determine the minimum length.
- The overlays are made of material whose thickness is at least 1/3 of the same size as the main board.
Nails are driven into the linings in two parallel rows with a staggered “dispersion” of fastening points. To avoid damaging the overlay, which is thin in relation to the main lumber, the number of attachment points is calculated based on the resistance of the nails shear force, acting on the legs of the hardware.
When the junction of the rafter parts is located directly above the support, there is no need to calculate nailing to fix the linings. True, in this case the docked leg will begin to work as two separate beams both for deflection and compression, i.e. according to the normal scheme, you will have to calculate the load-bearing capacity for each of the component parts.
If steel rod bolts or rods without threads, dowels are used as fasteners when joining thick boards or timber, then the threat of deformation will be completely eliminated. In fact, even some gaps in the joining of the ends can be ignored, although it is still better to avoid such flaws.
When using screws or screws, pre-drill holes for their installation; the Ø of the holes is 2-3 mm less than the same size of the fastener leg.
When making frontal connections of rafters, it is necessary to strictly observe the design installation pitch, the number and diameter of fasteners. When the distances between fixation points are reduced, wood splitting may occur. If the holes for the fasteners are larger than the required dimensions, the rafters will be deformed, and if they are smaller, the lumber will split during the installation of the fasteners.
Extension with composite rafters
To connect and increase the length of the rafters there is still quite interesting way: extension using two boards. They are sewn to the side planes of the extended single element. Between the extended parts there remains a gap equal to the width of the top board.
The gap is filled with scraps of equal thickness, installed at intervals of no more than 7 × h, where h is the thickness of the board being extended. The length of spacer bars inserted into the lumen is at least 2 × h.
Extension using two extension boards is suitable for the following situations:
- The construction of a layered system along two side girders, which serve as a support for the location of the joining area of the main board with the attached elements.
- Installation of a diagonal rafter that defines the inclined edge of hip and half-hip structures.
- Construction broken roofs. The strapping of the lower tier of rafters is used as a support for the connection.
Calculation of fasteners, fixation of spacer bars and connection of boards is carried out by analogy with the methods described above. For the manufacture of spacer bars, trimmings from the main lumber are suitable. As a result of installing these liners, the strength of the prefabricated rafter significantly increases. Despite the significant savings in material, it works like a solid beam.
Video about ways to build rafters
Demonstration of basic splicing techniques structural elements rafter system:
A video with a step-by-step description of the process of connecting rafter parts:
Video example of one of the methods of joining lumber:
Compliance with the technological requirements according to which the rafters are spliced along the length guarantees trouble-free operation of the structure. Extension methods can reduce roof construction costs. You should not forget about preliminary calculations and preparation for making connections so that the result of your efforts becomes ideal.
Connections of wooden elements have the task of connecting mating Construction Materials, for example, edged beams, so that they do not move relative to each other. According to the position and direction of the wooden elements being connected, longitudinal connections and corner connections, as well as connections on branches and crosses, are distinguished. Spatial connecting elements from steel sheet and plate steel plates with pre-drilled holes often replace carpenter joints.
Connections that must transmit forces of a certain magnitude and direction, such as compressive forces, are also called joints of connected wooden elements as rods, for example compressed rods. Compressed rods connected at an acute angle can be connected using notches. Other connections wooden structures are arranged at the expense of joints of wooden elements using connecting means.
Based on the type of connecting means, such connections are called nail or bolt, dowel or dowel connections. In wood construction, laminated veneers are also used. building construction. Because they have special advantages, the use of laminated timber structures is of increasing importance.
Longitudinal connections
There are longitudinal connections on supports and longitudinal connections in the span. Above the supports, perpendicular trunnions, a “toe-to-foot” joint and a partially “to-toe” trunnion joint are used (Fig. 1). To reinforce these joints, flat or round steel construction staples can be driven into the top or sides. Often wooden elements are butted head-on and secured only with construction staples. If, however, there are large tensile forces at the joint, for example, at purlins on the roof rafters, then both elements are butted head-on on a support and connected by side plates made of boards or perforated strips of corrosion-protected steel.
Rice. 1. Longitudinal connections
Purlins can also be made in the form cantilever-suspended(Gerber runs) or hinged purlins. Their joint is located in a place determined by calculation, not far from the support, in which the bending moments are equal to zero and where there are no bending forces (Fig. 2). There, the purlins are connected with a straight or oblique overlay. The incoming purlin is held in place by a screw bolt, also called a hinge bolt. The hinge bolt with washers must take the load from the suspended purlin.
Rice. 2. Longitudinal connections of Gerber purlins
Gerber purlins with a joint lying on top are impractical, since there is a danger that the purlins at the edge of the joint will come off. If the joint is suspended, if damaged, there is no danger of tearing off.
To connect Gerber purlins, spatial elements made of steel sheet are also used, which are also called Gerber connecting elements. They are attached with nails along the frontal butt ends of the purlins (see Fig. 2).
Corner connections
Corner joints are necessary when two logs or beams in a corner are joined at right or approximately right angles in the same plane. The most commonly used types of joints are cut-out trunnions, smooth corner foot and compressed foot (Fig. 3). With the help of cut-out trunnions and smooth corner paws, the ends of the thresholds, purlins and rafter legs lying on supports or protruding in a cantilever are connected. Nails or screws can be used to secure connections. The compressed paw has planes that enter each other obliquely. It is particularly suitable for connecting loaded, fully supported thresholds.
Rice. 3. Corner joints
Branches
When branching, a timber suitable at a right or oblique angle is in most cases superficially joined to another timber. In ordinary cases, a joint on axles is used, and in secondary structures a “claw” connection is also used. In addition, beams made of timber can be joined using metal spatial connecting elements. In trunnion joints, the thickness of the trunnion is approximately one third of the thickness of the beam. The axles have a length in most cases from 4 to 5 cm. The groove for the axle is made 1 cm deeper so that the compression force is transmitted not through the axle section, but through the large area of the remaining cross-section of the beams.
When arranging axles, a distinction is made between normal axles that extend across the entire width of the beam, and protruding(hemp) axles, which are used for connections at the ends of beams (Fig. 4). If the beams in the connection do not approach each other at right angles, for example, with corner struts, then the axle at the strut should be made at right angles to the horizontal (or vertical) structural element (see Fig. 4).
Rice. 4. Trunnion connections
When installing trunnions in wooden beams and purlins, the trunnion must bear the entire load. It is more advantageous to carry out such connections using beam shoes made of corrosion-protected steel (Fig. 9). These shoes are secured with special nails in such a way as to prevent them from buckling and turning relative to the joint. Besides, cross section the beams are not weakened by the holes for the trunnions.
Cross connections
Wooden beams can intersect in one plane or with offset planes and be overhead or supporting. Beams intersecting in the same plane can intersect “IN THE PAW” if the weakening of the section does not play any role (Fig. 5). It is advisable to connect the intersecting overhead thresholds on the support beams with round dowels (pins) made of hard wood or steel with a length of 10 to 12 cm (Fig. 6).
Rice. 5. “claw” connection
Rice. 6. Connection using round keys (pins)
Side-joining beams receive good support on the pole if their connection is made “IN THE GROOT” (Fig. 7). To do this, the intersection planes of both elements are cut to a depth of 1.5 to 2.0 cm. This results in a non-shifting connection, which is secured with a screw bolt.
Rice. 7. “Groove” connection
When joining inclined and horizontal beams, as is usually the case when joining rafter legs with purlins - thresholds, a cutout is made in the rafter leg corresponding to the slope, which is called sidebar(Fig. 8).
Rice. 8. Inset of rafter leg
Cut-in depth rafter legs with a normal section height of 16 to 20 cm, it is from 2.5 to 3.5 cm. For fastening, use one nail that penetrates the threshold to a length of at least 12 cm, or a special anchor for attaching the rafters to the purlins.
Rice. 9. Connection with steel shoe
Cuttings
When cutting, a compressed rod entering at an acute angle is connected to another beam using one or more force-transmitting planes on its front side. Based on the number and position of force-transmitting planes, a distinction is made between a frontal notch, a notch with a tooth, and a double frontal notch with a tooth.
At frontal cut(also called the frontal stop) the receiving beam has a wedge-shaped cutout corresponding in shape to the end of the compressed rod (Fig. 10). The frontal plane must pass at an angle dividing an obtuse external corner cuts in half. The fastening bolt must have the same direction, guaranteeing the joint against lateral displacement. To mark the notches, parallels are drawn at equal distances from the sides of the angle, which must be divided in half. The connecting line between the point of their intersection and the vertex of an obtuse angle will be the bisector of this angle (see Fig. 10). The position of the fastening bolt is obtained if the distance between the bisector and the end of the notch is divided into three parts parallel to the bisector (see Fig. 10).
Rice. 10. Frontal cut
Under the action of a compressive force, the wood lying in front of the frontal part of the compressed rod works to slice(see Fig. 10). Since the permissible stress for cutting wood along the fibers is relatively small (0.9 MN/m2), the plane of the wood in front of the cut edge (cut plane) must be quite large. Since, in addition, cracking due to shrinkage should be taken into account, then, with rare exceptions, the length of the cut plane should not be less than 20 cm.
At reverse or gear notch the notch plane is cut at a right angle to the underside of the compressed rod (Fig. 11). Due to the fact that due to the eccentric connection in a gear notch there may be a risk of splitting of the compressed rod, it is necessary that the free end of the notch does not fit tightly to the support rod and a seam is provided between them.
Rice. 11. Tooth cutting
Double cut consists, as a rule, of a frontal notch in combination with a gear notch (Fig. 12). The direction of the notch planes is the same as is customary for each of the notches of this combination. However, the serrated notch in this case must be at least 1 cm deeper so that its cut plane is lower than the cut plane of the frontal notch. The fastening bolt should run parallel to the frontal part of the notch approximately halfway between the bisector and the top of the acute joint angle.
Rice. 12. Double cut
Cutting depth t v is limited according to DIN 1052. The determining factors for this are the contact angle (a) and the height h of the cut rod (Table 1).
Pin and bolt connections
In case of pin and bolt connections wooden beams or boards touching their sides are connected by cylindrical connecting elements, such as rod dowels, bolts with recessed heads and nuts, ordinary bolts and nuts. These rod dowels and bolts are designed to prevent the wood members from moving in the joint plane, also called the shear plane. In this case, forces act perpendicular to the axis of the rod dowel or bolt. Dowels and bolts work in bending. In connected wooden elements all efforts are focused on inner surface holes for dowels or bolts.
The number of rod dowels and bolts installed at the junction depends on the magnitude of the transmitted force. In this case, as a rule, at least two such elements should be installed (Fig. 13).
Rice. 13. Connection using rod dowels
In a single joint, many shear planes may be located adjacent to each other. Based on the number of cut planes that are connected by identical connecting elements, single-cut, double-cut and multi-cut dowel and bolt connections are distinguished (Fig. 14). According to DIN 1052, single-cut load-bearing connections using dowel rods must have at least four dowel rods.
Rice. 14. Bolted connections
For bolted connections, bolts and nuts made of steel with standardized diameters of 12, 16, 20 and 24 mm are mainly used. To prevent the head and nut of the bolt from cutting into the wood, strong steel washers should be placed under them. Minimum dimensions these washers are provided for various diameters bolts in DIN 1052 (Table 2).
To prevent splintering of the connected wooden elements by the core dowels and bolts, these connecting means must be installed minimum distances between themselves, as well as from the loaded and unloaded ends. The minimum distances depend on the direction of the force, on the direction of the wood grain and on the diameter of the dowel rod or bolt db and do (Fig. 15 and 16). For load-bearing bolts and nuts, greater distances must be maintained between each other and from the loaded end than for rod dowels and bolts with hidden heads. But dowel rods or bolts with hidden heads located close to each other in the direction of the wood fibers should be spaced apart relative to the cut line so that the joints do not crack (see Fig. 15).
Rice. 15. Minimum distances for dowel rods and hidden head bolts
Rice. 16. Minimum distances in case of load-bearing bolts
Holes for pins and bolts are pre-drilled perpendicular to the cutting plane. For this purpose, electric drills with a frame with parallel movement are used. For pins when drilling holes in wood, as well as when simultaneously drilling holes in wood and metal connecting elements The diameter of the hole must match the diameter of the pin.
Also, the holes for the bolts should be well suited to the diameter of the bolts. The diameter of the hole cannot be increased compared to the diameter of the bolt by more than 1 mm. At bolted connections It's bad when the bolt sits loosely in the hole. It is also bad if, due to shrinkage of the wood, the clamp of the bolt in the hole gradually weakens. In this case, a backlash appears in the cut plane, which leads to even greater pressure from the bolt rod on the boundary planes of the hole walls (Fig. 17). Due to the associated flexibility, bolted connections cannot be used indefinitely. For simple buildings, such as sheds and sheds, as well as scaffolding, they can, however, be used. In any case, in the finished structure, the bolts must be tightened many times during operation.
Rice. 17. Backlash in bolted connections
Dowel connections
Dowels are fasteners made of solid wood or metal that are used together with bolts to connect smoothly joined wooden elements (Fig. 18). They are positioned in such a way that they act evenly on the surface of the elements being connected. In this case, the transmission of forces occurs only through the dowels, while the bolts provide a clamping effect in the connection so that the dowels cannot tip over. Slats made of flat or profile steel are also attached to wooden elements using dowels. To do this, use single-sided dowels or flat steel dowels. There are dowels various forms and types.
Rice. 18. Connecting wooden elements using dowels and bolts
When making dowel connections with pressed-in dowels, holes for the bolts are first drilled in the elements being connected. After this, the wooden elements are again separated, and a groove is cut, if necessary, for the main plate. Depending on the construction technology, the dowel is completely or partially driven into the groove of one of the elements being connected using a mallet. For final clamping of a precisely aligned connection, special clamping bolts with a large washer are used. Connections with many or large pressed-in dowels are clamped using hydraulic press. When connecting with a large number dowels, as happens when installing corner connections in frames made of laminated board elements, it is more preferable to use round plug-in dowels, since with pressed-in dowels the press-in pressure may be too high (Fig. 19).
Rice. 19. Dowel connection in the corner of the frame
Each dowel, as a rule, must correspond to one bolt and nut, the diameter of which depends on the size of the dowel (Table 3). The size of the washer is the same as for bolted connections. Depending on the magnitude of the force acting on the connection, larger or smaller dowels can be used. The most common diameters are from 50 to 165 mm. In the drawings, the size of the dowels is indicated by symbols (Table 4).
| Table 3. Minimum dimensions for dowel connections | ||
| Outer diameter d d in mm | Bolt diameter d b in mm | Distance between dowels/distance from dowel to the end of the element, e db, in mm |
| 50 | M12 | 120 |
| 65 | M16 | 140 |
| 85 | M20 | 170 |
| 95 | M24 | 200 |
| 115 | M24 | 230 |
| The values are valid for the family of round press-in dowels type D. | ||
| Table 4. Drawing symbols for special types of dowels | |
| Symbol | Dowel size |
 |
from 40 to 55 mm |
 |
from 56 to 70 mm |
 |
from 71 to 85 mm |
 |
from 86 to 100 mm |
 |
Nominal dimensions > 100 mm |
At placement of dowels You should maintain certain distances between the dowels and from the edges of the wooden elements. These minimum distances according to DIN 1052 depend on the type of dowel and its diameter (see Table 3).
The bolts and nuts of dowel joints are almost always passed through the center of the dowel. Only with rectangular and flat steel dowels do they lie outside the plane of the dowel. When tightening the nuts on the bolts, the washers should cut approximately 1mm into the wood. For dowel joints, the nuts on the bolts must be tightened again several months after installation so that their tightening effect remains even after the wood shrinks. They talk about a connection with constant force transmission.
Load-bearing dowel connections
Load-bearing dowel (nail) connections have the task of transmitting tensile and compressive forces. With the help of dowel connections, load-bearing parts can be fastened, for example, for simply supported trusses, as well as structures made of boards and beams. Dowel connections can be made single-cut, double-cut and multi-cut. In this case, the size of the nails must correspond to the thickness of the lumber and the depth of driving. In addition, when placing nails, certain distances between them must be maintained. In load-bearing dowel connections, holes should be drilled in advance. The drilled hole should be slightly smaller in diameter than the diameter of the nail. Since this does not cause the wood to crack as much, the nails can be placed closer together in this way. Besides, load bearing capacity the nail joint will increase and the thickness of the wood can be reduced.
Single shear dowel connections are used when compressed and stretched rods from boards or beams must be attached to the beams (Fig. 20). In this case, the nails pass through only one connecting seam. They are loaded there perpendicular to the hole shaft and can bend if too much force is applied. Since shear forces also arise in the connecting seam in the body of the nail, this section plane is called the shear plane. In the case of paired connection of plank rods on the planes of the main beam, there are two single-cut dowel connections opposite each other.
Rice. 20. Single-cut dowel connection
At double shear dowel connections the nails pass through the three wooden elements being connected (Fig. 21). The nails have two cutting planes, since they are loaded with the same directional force in both connecting seams. Therefore, the load-bearing capacity of a double-shear loaded nail is twice that of a single-shear nail. To prevent double-cut dowel joints from coming apart, half the nails are driven in on one side and the other half on the other. Double-shear dowel connections are mainly used if simply supported trusses consist entirely or predominantly of boards or beams.
Rice. 21. Double-cut dowel connection
Minimum thicknesses of wooden elements and minimum nailing depth
Since thin wooden elements easily split when hammering nails, the boards for load-bearing rods, belts and planks must be at least 24 mm thick. When using nails from size 42/110, use even larger ones minimum thicknessA(Fig. 22). They depend on the diameter of the nail. With dowel joints with pre-drilled holes, the minimum thickness of wood will be less than with simple nailing, since there is less risk of cracking.
Rice. 22. Minimum thickness and driving depth
The distance of the nail tip from the closest cutting plane is called the driving depth. s(see Fig. 22). It depends on the diameter of the nail dn and has a different value for single-cut and double-cut nail connections. Single shear loaded nails must have a driving depth of at least 12dn. However, for certain special nails, due to the greater holding force due to the special profiling, a driving depth of 8d n is sufficient. For double-shear connections, a driving depth of 8dn is also sufficient. With a shallower driving depth, the load-bearing capacity of the nails decreases. If nails have a driving depth of less than half the required, then they cannot be taken into account for the transmission of forces.
Minimum distances between nails
Fastening of formwork, slats and fillies, as well as rafters, lathing, etc. acceptable using less than four nails. However, in general, a minimum of four nails are required for each seam or multiple nail joint intended to transmit forces.
The uniform arrangement of these nails on the connection plane is done using nail marks(Fig. 23). To ensure that two nails located one behind the other do not sit on the same fiber, they are shifted relative to the point of intersection of mutually perpendicular nail marks by the thickness of the nail in both directions. In addition, minimum distances must be maintained. They depend on whether the direction of force is parallel or across the fibers. Next, it is necessary to monitor whether the ends of the rods or the edges of the wood will be loaded by the force acting in the connection or not. Since there is a danger of cracking when the ends of the rods or edges are loaded, it is necessary to maintain large distances from the edges to the nails.
Rice. 23. Minimum distances between nails for a single-cut connection
At single shear nail connection vertical or diagonal stretched rod with nails with a diameter d n ≤ 4.2 mm, the minimum distances shown in Fig. 23. When using nails with a diameter d n > 4.2 mm, these distances should be increased slightly. If nail holes are pre-drilled, shorter distances are required in most cases.
At double shear nail connections the nails are arranged in ledges. Between the risks of a single-shear nail connection, additional risks are drawn with a minimum distance of 10d n (Fig. 24).
Rice. 24. Minimum distances between nails for a double-cut connection
Installation of nail connections
When making nail connections, the nails must be driven vertically into the wood. In this case, the nail head should only be slightly pressed into the wood so that the wood fibers at the joint are not damaged. For the same reason, the protruding ends of the nails can only be bent in a special way. This should only occur perpendicular to the grain. To apply the location of nails, as a rule, appropriately drilled templates made of thin plywood or tin are used. In the case of plywood templates, the holes are made of such a diameter that the nail heads can pass through them. In the case of templates made of tin, the locations of the nails are marked with a brush and paint.
Nail connections with steel plates
Nail connections with steel plates can be divided into three types, namely connections with embedded or externally lying plates with a thickness of at least 2 mm and connections with embedded plates with a thickness of less than 2 mm.
Externally lying pads usually have in advance drilled holes(Fig. 25). They are placed over the joint of beams or boards at the end and nailed with the appropriate number of wire or special nails. At embedded overlays with a thickness of at least 2 mm nail holes must be drilled simultaneously in the wood members and in the trims. In this case, the diameter of the holes must correspond to the diameter of the nail. Embedded overlays with thickness less than 2 mm, of which there may be several at the joint, can be pierced with nails without pre-drilling (Fig. 26). Such connections can only be made using specially designed spline tools and only with special approval from the authorities.
Rice. 25. Connection using a perforated steel plate-plate
Rice. 26. Nail connection with embedded steel plates (Greim)
Connections using nail gussets
Nail gussets are used for the rational production of wooden half-timbered trusses from single-row sections of wood (Fig. 27). To do this, wooden rods of equal thickness are cut to length, impregnated and adjusted exactly to each other.
Rice. 27. Connection using a nail gusset
The moisture content of the wood should not exceed 20%, and the difference in thickness should not be more than 1 mm. In addition, the rods should not have any cuts or edges.
The nail gussets must be positioned symmetrically on both sides and, using a suitable press, pressed into the wood so that the nails sit in the wood to their full length. Driving nail heads using a hammer or the like is not permitted.
Fastening with nail gussets creates a connection or joints that are strong in compression, tension and shear at nodal points without weakening the load-bearing section of the wood. For the transmission of forces, the main importance is the working area of the connection of the nail gusset (Fig. 28). It corresponds to the area of contact of the nail gusset with the wood, with the exception of the edge strip with a width of at least 10 mm.
Rice. 28. Working area of the connection at the nail gusset
Trusses with gusseted connections of rods are industrially manufactured only by licensed enterprises, delivered ready-made to the construction site and installed there.
When making any carpentry products There are often times when the length of the board is not enough. As luck would have it, instead of one long one there are several short ones. In this case, experienced carpenters do not run to the store or to the sawmill, but increase the length of the timber. Refurbished products are not used in all cases. For example, it is better not to use them for seats on benches or for the floor, but for door panels or rafters, connected planks are quite suitable.
Behind long years As humans work with wood, many ways to connect boards to each other have emerged. We will look at one of these techniques in this article.
So, we have 3 ties that need to be connected to each other lengthwise. It should be noted here that the fewer segments are used for splicing, the stronger the connected array will be. In our case, it turned out that one plank was not enough to make the canvas. Therefore, I had to join it together from three short pieces. Of course, the parts of the planks for splicing must be equal in width.
First of all, let's mark the gaps. Let's connect them into half boards, that is, cut half the width from one segment, half from the other. Part of one gorge will overlap another. A length of 10-15 cm for the cutout will be quite enough, but the longer this distance, the stronger the connection will be. It is important to take into account that when marking the segments, you need to remember the length for which the cut is planned. For example, if you want to make a connected board 200 cm long, then the total length of the two sections should be greater by the distance at which you plan to make the cut. With a 15 cm cut, the length of the two boards will be 215 cm. At a 15-centimeter distance, one part of the board will fit into the other, and the total length will be 200 cm.
In the same way we will make a cutout on segments 2 and 3.
Now the planks need to be fastened together. We will use furniture dowels for these purposes. On two sections we will make marks opposite each other and drill holes with a depth equal to half the dowel. Let's drop into the holes furniture glue and hammer the dowel so that it sticks out halfway. We will also add a drop of glue into the holes on the second board and connect the segments together. Two dowels for connection will be quite enough.
Let's join the third part of the gorge in exactly the same way.
Next, we will increase the bending strength of the connected array. For this we need a hand router.
Let's install it on it slot cutter with a diameter of 2 cm and set the cutting depth to be slightly more than half the thickness of the board. The main thing here is not to cut through the boards. Using a router, we make two grooves on each side, capturing all 3 jointed boards. We will make 4 grooves in total, each about 15 cm long.
We will insert into these grooves wooden blocks, cutting them out from the remains of the gorge. It turns out something like dowels, only these dowels hold two bars in the same plane. The bars must fit into the grooves with force so that they do not move. We smear the grooves with wood glue, insert the keys and hammer them in until they stop. The height of the bars is not important here.
We plan off the excess parts of the bars with a plane.
To prevent the keys from jumping out of the grooves if the board dries out, we will drill into them through holes, insert furniture dowels and hammer them into the entire thickness of the timber. We plan the protruding parts of the dowels again with a plane.
At this stage, the connection of the boards to each other is completed. Then they begin Finishing work to remove gaps if necessary. Let's take a universal putty and rubber spatula Let's fill the gaps.
After a couple of hours, when the putty is completely dry, we sand the tarmac grinder. Now the connected board is ready for use.
In our case, it was inserted into door leaf. After making the door and painting it, it became completely invisible that the board consisted of several parts. And this does not affect the strength in any way.
VIDEO
Typically, timber products such as beams, planks or planks come in a specific size, but construction often requires materials that are longer, wider or thicker. Therefore, to obtain required sizes exist different kinds connections using notches, which are made manually according to markings or with special equipment.
Width connections
When joining narrow boards, boards of the required size are obtained.
There are several ways to connect.
1) Joint with a smooth reveal;
With this joining method, each strip or board is called a plot, and the seam that is formed as a result of the connection is called a fugue. The quality of jointing is indicated by the absence of gaps between the joints of the edges of adjacent plots.
2) Rail connection;
Grooves are selected along the edges of the plots and inserted into their slats, which fasten the plots together. The thickness of the slats and the width of the groove should not exceed 1/3 of the thickness of the board.
3) Quarter connection;
In plots that are fastened, quarters are selected along the entire length. In this case, the dimensions of the quarter, as a rule, do not exceed half the thickness of the plot.
3) Tongue and groove connection (rectangular and triangular);
This type of connection provides the plot with a groove on one side and a ridge on the other. The comb can be either rectangular or triangular, but the latter is rarely used as its strength is slightly inferior. The tongue and groove joint is quite popular and is often used by parquet manufacturers. The disadvantage of this connection is considered to be lower efficiency, since more boards are used.
4) Dovetail connection;
This type of fastening is a little similar to the previous one, only the comb has a trapezoidal shape. Well, hence the name.
Also, when assembling panels, dowels, tips in a groove and a comb are used with a lath glued into the end. Among the glued slats, there are triangular, rectangular and glued ones, and when using dowels, the dovetail groove is mainly chosen. All this is needed to securely fasten the shield.
Length connection
Popular types of joints along the length include: end-to-end, tongue-and-groove, tongue-and-groove, toothed adhesive joints, quarter joints, and rail joints. The toothed connection is the most popular because it has better strength.
There is also splicing, where longer sections are joined together. This can happen in several ways. For example, half-tree, oblique cut, oblique and straight overlay lock, oblique and straight tension lock and end-to-end. When choosing half-timber splicing, the required joint length should be 2 or 2.5 times the thickness of the timber. For greater reliability, dowels are used, for example, this can be found in the construction of cobblestone houses.
When using an oblique cut with trimming the end, the dimensions are 2.5 - 3 times the thickness of the beam and are also secured with dowels.
A connection with a straight or oblique patch lock is used in structures in which tensile forces are present. A straight rim lock is located on a support, and an oblique lock can be placed near the supports.
If you decide to use an oblique cut with an end trim, then the connection should have 2.5 or 3 times the thickness of the timber. In this case, dowels are also used.
When joining with a straight or oblique tension lock, you don’t have to worry about strength, but such a connection is difficult to manufacture, and when the wood dries out, the wedges weaken, so this joining method is not suitable for serious structures.
A butt splice is when the two ends of a beam are placed on a support and securely connected with staples.
The connection of beams or logs can be found during the construction of walls or in the upper or lower frame in frame houses. The main types of joints include half-tree, half-foot, tenon and corner frying pan.
Half-tree cutting is cutting down or cutting off half the thickness at the ends of the beams, after which they are connected at an angle of 90 degrees.
A half-foot joint is formed by cutting inclined planes at the ends of the beams, thanks to which the beams are tightly connected. The size of the slope is determined by the formula.
Cutting with a corner frying pan is very similar to cutting half a tree, but distinctive feature is that with such a connection one of the beams loses a small part in width.
Height connection
A cross-shaped connection of beams can be found during bridge construction. With this method, you can use a half-tree connection, a third and a quarter of a tree, or notching one beam.
Building up
Building up beams and logs is the connection of elements in height, which is often used in the construction of pillars or matches.
There are several types of extensions:
1) end-to-end with a hidden tenon;
2) end-to-end with a through ridge;
3) half-tree with bolt fastening;
4) half-tree with fastening with clamps;
5) half-wood with strip steel fastening;
6) an oblique cut with fastening with clamps;
7) end-to-end with overlays;
8) bolting;
The length of the joints is usually 2-3 times the thickness of the beams being connected or 2-3 times the diameter of the logs.
Tenon connection
When tenoning bars, a tenon is cut on one, and an eye or socket is made on the other. Tenon joints are often used to create joinery, doors, windows or transoms. All connections are made with glue. You can use not only one, but also two or more spikes. The more thorns, the larger area gluing. This type of connection can be divided into corner end, corner middle and corner box.
With an angular end connection, an open through tenon (one, two or three), a tenon with a through and non-through darkening, and insert dowels are used. Corner middle connections can be found on doors. Corner middle and end joints can additionally use nails, screws, dowels or bolts.
Well, that’s probably all about connection types. This does not include connections made with nails, screws or bolts. Pure wood and a little glue. :)
