The coolest joiners and carpenters are said to be able to build a house without a single nail. Japanese artisans, even amateurs, are just that.
A few years ago, a young and passionate automotive industry worker came across a book describing traditional Japanese woodworking techniques. He was very fascinated by the descriptions of the connections of parts without the use of nails, screws and glue. He wanted to learn how to do the same. But there were no diagrams for making fasteners in the book. Then the guy decided to draw them himself.
He used the free service Fusion-360 to model and animate the parts. The Japanese translated the resulting result into GIFs and posted it on a Twitter account called The joinery... In almost a year, the young carpenter visualized 85 different ways detachable connections.
The variety of mounts is truly amazing. With their help, you can make basically anything - a stool, a sofa, a table, and so on. The main thing is to have straight arms and a good, preferably electric tool.
But even if the manual labor does not inspire you at all, you will probably enjoy watching GIFs. The grace with which the details mesh with each other is mesmerizing.
If you take a closer look at massive antique furniture or doors, you will notice a beautiful and uniform texture: the product seems to be carved from one large piece of wood. Only on closer inspection can you single out the individual planks, which make up the common surface.
Previously, furniture was not made, as is done today, from thick boards. The carpenters were just more skilled. From many thin planks, they could make a large panel with a perfectly smooth surface. Although the tree is known to live its contented hectic life, even when it is no longer connected by its roots 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 the planks so that they remain even and smooth for a long time is called butt joining along the length.
It is necessary to carefully examine each plank and compare its texture with the texture of the adjacent parts: the wood fibers of each part should run in the opposite direction compared to the fibers of the adjacent planks. So one board "locks" the other.
The nature of the texture depends on whether the board is cut from the middle or extreme part of the trunk. Boards can be laid out in different ways: in one case, so that the surface will seem to be a cut from one trunk, in the other, by mixing the boards, create an unusual pattern.
But in any case, when fitting, the boards should be positioned 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, one can see alternately the front (facing the core of the tree), then the seamy (facing the bark) side of the boards.
In order for the boards to fit snugly against each other along the length, the edges must be absolutely straight. You need to vertically fix the board between two guide boards and treat the surface with a plane. Process the wood immediately, without delay - if the air humidity changes, it may deform again.
The table top, assembled from boards, used to be judged on the skill of the carpenter. The ability to join boards end-to-end lengthwise can still be useful today. We will show and tell you how this is done.
Marking and gluing
The plank reinforces the joint along the entire length, while performing two functions: it doubles the area of the joint areas covered with glue, since it penetrates into 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 the connection is more resistant to stress.
For a bar that must be very thin, the most suitable material- plywood. If, for example, you take a solid wood plank, then the arrangement of the fibers in the plank and planks will be parallel. In this case, a high joint strength will be achieved, but the bar itself will not withstand the load and will break if the boards begin to bend. A bar with crosswise grain direction can be used. It withstands well the load during bending of the boards and gives great strength to the joint, but such strips are limited in length and are extremely unreliable under longitudinal loads. Multi-ply plywood compensates for the imperfections of the solid wood planks, providing a strong connection.
An alternative to the rail is plug-in spikes, which are placed with a glue fit at a distance of 10-20 cm from each other. First, a hole for the thorns is drilled in one board, then the location of the thorns 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 total height of the grooves to leave room for the glue.
Blind connection using plywood planks. The plank is completely hidden, and the boards at the ends remain intact.
Since ancient times, after mastering the tools of labor, man began to build a dwelling made of wood. Having gone through evolution, man for millennia continues to improve the construction of his home. Sure modern technologies simplified construction, gave ample opportunity for imagination, but basic knowledge of the properties wooden structures passed from generation to generation. Consider ways to connect wooden parts.
Consider the methods of joining wooden parts that novice craftsmen encounter. Basically, these are carpentry connections, passed down from generation to generation, these skills have been used for more than one century. Before we start joining wood, we assume that the wood is already processed and ready for use.
The first basic rule that should be followed when joining wooden parts is that a thin part is attached to a thicker one.
The most common ways of joining wood, which will be needed in the construction of homestead buildings, are of several types.
This is one of the most simple ways connections (rallying). With this method, it is necessary to fit the surfaces of the two elements to be connected as closely as possible. The parts are pressed tightly against each other and fastened with nails or screws.
The method is simple, but to obtain the quality of the product, several conditions must be met:
The length of the nails should be such that, having passed through the entire thickness of the first workpiece, their sharp end entered the base of another part to a depth equal to at least ⅓ of the length of the nail;
Nails should not be located in one line, and their number should be at least two. That is, one of the nails is shifted upward from the centerline, and the other, on the contrary, downward;
The thickness of the nails must be such that no crack appears in the wood when they are hammered. Pre-drilling the holes will help to avoid the appearance of a crack in the wood, and the drill diameter should be equal to 0.7 of the diameter of the nails;
To receive best quality the joints, the surfaces to be connected must first be well lubricated with glue, and it is better to use a moisture-resistant glue, for example, epoxy.
In this method, two pieces are stacked on top of each other and held together with nails, screws or bolts. Wooden blanks, with this method of joining, can be placed in one line or displaced at a certain angle relative to each other. In order for the angle of joining the blanks to be rigid, it is necessary to fasten the parts with at least four nails or screws in two rows of two in a row.
If you are fastening with only two nails, screws or bolts, then position them diagonally. If the nails will have a through exit through both parts, with the subsequent bending of the protruding ends, this method of connection will significantly increase the strength. The connection in the invoice does not require high qualifications of the master.
This method is more complicated, it requires certain skills and a more scrupulous approach to work. For such a connection, in both wooden blanks, a sample of wood is made at a depth equal to half of their thickness, and a width equal to the width of the parts to be joined.
You can connect parts in half a tree at different angles.
It is important to observe the following rule:
So that the angle of the sample on both parts is equal, and the width of both samples strictly corresponds to the width of the part. If these conditions are met, the parts fit tightly to each other, and their edges will be located in the same plane. The connection is fastened with nails, screws or bolts, and glue is still used to increase strength. If necessary, such a connection can be partial. That is, the end of one of the blanks is cut at a certain angle, and the corresponding selection is made in the other part. This connection is used for corner joining. In this case, both thorns (samples) are cut at an angle of 45 degrees, and the joint between them is located diagonally.
Such splicing of bars and beams along the length has its own characteristics.
For vertical supports, splicing is simple.
But it is a completely different matter when a beam or a beam at the splice is subject to bending or torsion loads, in which case a simple fastening with nails or screws cannot be dispensed with.
The parts to be spliced are cut at an angle (into an oblique pad) and compressed with bolts. The number of bolts depends on the applied loads, but there should be at least two of them.
Sometimes additional overlays are installed, for example, metal plates, preferably on both sides, top and bottom, for strength, you can additionally fasten with wire.
Such a connection is used for flooring or for cladding boards. To do this, a spike is made in the face of one board, and a groove in the other.
With such a splicing, gaps between the boards are excluded, and the sheathing itself acquires beautiful view... Properly processed sawn timber goes to the trade network, where they can be purchased ready-made.
An example of such materials is a floorboard or wall paneling.
This is one of the most common joining of wooden parts.
Such a connection will provide a strong, rigid and neat cohesion.
It goes without saying that it requires certain skills and accuracy in work from the performer.
When performing this connection, you need to remember that a poor-quality spike connection will not add reliability and will not have a beautiful appearance.
A spike connection consists of a groove, hollowed out or drilled in one of the wooden parts, as well as a spike made at the end of another attached element.
The parts should have the same thickness, but if the thickness is different, then the socket is made in the part that is thicker, and the spike is made in the second, thinner part. The connection is made on glue with additional fastening with nails, screws. When screwing in the screw, remember that pre-drilling will make this process easier. It is better to conceal the head of the screw, and the pilot hole should be ⅔ of the screw diameter and be 6 mm less than its length.
One of the very important conditions is the same moisture content of the parts to be joined. If the elements to be joined have different humidity, then when dry, the spike will decrease in size, which will lead to the destruction of the entire connection. That is why the parts to be joined must have the same humidity, close to the operating conditions. For outdoor structures, humidity should be in the range of 30-25%.
Choice of wood.
In carving, for making large crafts with large elements, they often use wood conifers as the main one. They are available and the striped texture can be played up in ornaments.
As a background for the applied and cut threads, it is used fir.
A valuable material is cedar, its soft, with a beautiful texture and pleasant yellow-pink or light-pink color of the core of the wood. The wood is easy to cut, cracks a little during shrinkage and is resistant to decay.
Wood pears It is used for highly artistic thread details, as it is durable and has little warping from weathering.
Poplar, the wood is very soft and light - it is used to make carved decorative columns or backboards for attaching an overhead thread.
It is good to use wood for making chains from round rings. apple trees... This wood is used in small crafts, in applied carving. In this case, the springy properties of the apple tree are used.
Wood is also used linden trees... Very lightweight, planes well, drills and grinds well.
Thread from oak laborious to manufacture due to its hardness.
But the oak is not afraid of moisture, does not warp. Products made from natural wood are very beautiful, but affordable. To reduce the cost of the product, veneering is used. For example, veneered doors are made, according to the customer's order, "oak". We get beautiful doors, outwardly similar to natural ones, but at a much lower price.
What could be simpler than connecting wooden parts with a "mustache"? Despite the simplicity of the method, sometimes difficulties arise with the accuracy and accuracy of the connections. In this article, we will give you simple tips that you can use to achieve incredible results. Your corner joints will always be perfect!
It doesn't matter what you do: a photo frame or a trim for a furniture facade, make sure that the color of the wood, as well as the direction and structure of the fibers on the blanks, match. It takes a little time to select parts with a similar structure, but the result is excellent connections.
If you've ever tried adjusting yours by a few tenths of a degree, you know how difficult it is to do it. We offer you an easy way to solve this problem: stick on cross stop several sheets of paper for notes. Thus, making test cuts and removing one sheet at a time, you will achieve the ideal cutting angle.
To accurately determine the length of the trim element, you need to try it on to the panel. This is easy to do if you attach the trim to the trim panel.
It is often not easy to evenly position the parts relative to each other and clamp them in the clamps, especially when the parts are lubricated with slippery glue. That is why woodworkers use dowels, even in cases where additional strength of the joint is not required.
On some clamps, when assembling the frames, you need to additionally make sure that all corners are connected at 90 degrees. Using corner clamps, there is no need for additional measurements of angles and setting diagonals.
Sometimes it is difficult to quickly apply glue to joints, assemble frames and clamp them in clamps without haste and fuss before the glue begins to set (often open time glue is less than 5 minutes in a warm and dry place). To increase the open time of the glue, you can thin it slightly with water. However, do not overdo it - if there is too much water, the bond strength may decrease.
Profiled workpieces are not always convenient to face - chips may appear, they are not always easy to clamp in clamps - the outer profile of the product can be damaged. Therefore, simplify your life - first assemble and glue the frame from rectangular blanks, and after the glue dries, profile hand milling cutter or at
When making a frame structure, the pieces on opposite sides of the piece should be the same length. To make sure of this, run a simple test. Fold the two pieces together and slide your finger along the ends. There should be no drops. You may not notice the difference in length by eye, but you will definitely feel even the smallest discrepancy in the length of the workpieces.
If, in the process of assembling products, you still did not manage to avoid cracks at the corners of the joints, do not despair. Just close them by pressing the corners to the center of the joint with a blunt, smooth object. You will be surprised, but the gap will disappear, while appearance the product will not deteriorate at all. Believe me, even experienced craftsmen use this method.
If the last part of your harness is slightly shorter than the opposite, you can cut it along the inside. And after assembly, cut off the rest of the parts on the outside. Thus, the width of the strapping will decrease slightly. If this, for example, is not a furniture facade, then no one will notice anything.
Connections of wooden elements have the task of connecting mating Construction Materials such as edging beams, so that they do not move relative to each other. According to the position and direction of the connected wooden elements, longitudinal joints and corner joints, as well as joints at branches and crossings, are distinguished. Spatial sheet steel connectors and pre-drilled sheet steel cover plates often replace carpentry joints.
Joints that must transmit forces of a certain magnitude and direction, for example compressive forces, are also called joints of the connected wooden elements as rods, for example, compressed rods. Compressed rods, connected at an acute angle, can be connected at notches. Other joints of wooden structures are made by joining the wooden elements with the help of connecting means.
By the type of connecting means, such connections are called nail or bolted, dowel or dowel connections. Glued wood is also used in wood construction. building construction... As they have particular advantages, the use of glued timber structures is of increasing importance.
There are longitudinal connections on supports and longitudinal connections in the span. Above the supports, perpendicular pins are used, a joint "in a paw" and a partially trunnion joint "in a paw" (Fig. 1). To reinforce these joints, flat or round steel construction brackets can be driven in from the top or from the side. Often, wooden elements are joined to the forehead and secured only with construction brackets. If, however, large tensile forces act at the joint, for example at girders on the roof rafters, then both elements are joined head-on on the support and are connected by side planks or perforated strips of corrosion-protected steel.
Rice. 1. Longitudinal connections
The runs can also be made in the form cantilever-suspended(Gerber runs) or articulated girders... For them, the joint is located in the place determined by the 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 girders are connected with a straight or oblique overlay. The incoming girder 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 girders
Gerber runs with a joint lying on top are impractical, since there is a danger that the runs at the edge of the joint will come off. When the joint is suspended, spitting, there is no danger of separation.
To connect Gerber girders, spatial elements made of steel sheet are also used, which are also called Gerber connecting elements. They are attached with nails along the frontal abutting ends of the purlins (see Fig. 2).
Corner joints are necessary when two logs or beams in a corner are joined at a right or approximately right angle in the same plane. The most commonly used types of joints are notched trunnions, smooth angled foot and compressed foot (Fig. 3). With the help of cut pins and smooth corner legs, the ends of the thresholds, girders and rafter legs lying on the supports or protruding cantilever are connected. Nails or screw bolts can be used to secure the connections. The compressed paw has planes obliquely entering each other. It is especially suitable for joining loaded, fully supported sills.
Rice. 3. Corner connections
When branching off, a beam suitable at a right or oblique angle in most cases superficially butts with another beam. In normal cases, a joint on the trunnions is used, and in secondary structures also a joint "in the paw" is used. In addition, timber beams can be joined using metal connecting space elements. In trunnion joints, the trunnion thickness is approximately one third of the bar thickness. The trunnions have a length in most cases from 4 to 5 cm. The groove for the trunnion is made 1 cm deeper so that the compression force is transmitted not through the section of the trunnion, but through large area the remaining section of the beams.
When arranging trunnions, normal trunnions are distinguished, passing through the entire width of the beam, and protruding(hemp) pins, which are used for connections at the ends of the bars (Fig. 4). If the beams in the joint do not fit at right angles to each other, for example at corner struts, then the trunnion at the brace must be made at right angles to the horizontal (or vertical) structural element (see Fig. 4).
Rice. 4. Connections with trunnions
When installing pins in wooden beams and girders, the trunnion must carry the entire load. It is more advantageous to carry out such compounds using girder shoes made of corrosion-resistant steel (fig. 9). These shoes are secured with special nails in such a way as to prevent them from skewing and turning relative to the docking point. Besides, cross section the beam is not weakened by the trunnion holes.
Wooden beams can intersect in the same plane or with offset planes and be overhead or support. Bars intersecting in one plane can intersect "IN THE PAW" if the weakening of the section does not play any role (Fig. 5). It is advisable to tie intersecting overhead thresholds on the support beams with round dowels (pins) made of solid wood or steel from 10 to 12 cm in length (Fig. 6).
Rice. 5. Connection "in the paw"
Rice. 6. Connection with round keys (pins)
The bars joining on the side get good support on the post, if their connection is made "IN PAZ" (Fig. 7). For this, the planes of intersection of both elements are cut to a depth of 1.5 to 2.0 cm. In this case, a non-displaceable connection is obtained, which is fixed with a screw bolt.
Rice. 7. Groove connection
When joining inclined and horizontal beams, as is usually the case when joining rafter legs with girders - thresholds, a cut is made in the rafter leg corresponding to the slope, which is called inset(fig. 8).
Rice. 8. Inset of the rafter leg
The depth of the inset in the rafter legs at a normal section height of 16 to 20 cm is from 2.5 to 3.5 cm. One nail is used for fastening, penetrating the threshold for a length of at least 12 cm, or a special anchor for attaching the rafters to the girders.
Rice. 9. Steel shoe connection
In the case of notches, a compressed rod entering at an acute angle is connected to another bar using one or more force-transmitting planes on its frontal side. According to the number and position of the force-transmitting planes, a frontal cut, a cut with a tooth and a double frontal cut with a tooth are distinguished.
At frontal cut(also called a frontal stop) the receiving bar has a wedge-shaped notch that matches the shape of the end of the compressed rod (Fig. 10). The frontal plane should pass at an angle dividing the obtuse outer corner cuts in half. The fastening bolt must have the same direction, guaranteeing the joint against lateral displacement. To mark the cuts, parallels are drawn at the same distance from the sides of the corner, which must be halved. The connecting line between the point of their intersection and the apex of the 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 cut is divided into three parts parallel to the bisector (see Fig. 10).
Rice. 10. Frontal notch
Under the action of the compressive force, the wood lying in front of the frontal part of the compressed bar works on slice(see fig. 10). Since the permissible stress on a cut of wood along the grain is relatively small (0.9 MN / m 2), the plane of the wood in front of the cut edge (cut plane) should be large enough. 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 toothed groove the plane of the notch is cut at right angles to the underside of the compressed rod (fig. 11). Due to the fact that due to the eccentric connection in the toothed groove there can be a risk of splitting the compressed rod, it is necessary that the free end of the groove does not fit snugly against the support rod and a seam is provided between them.
Rice. 11. Serrated notch
Double cut consists, as a rule, of a frontal cut in combination with a toothed cut (Fig. 12). The direction of the cut planes is the same as for each of the cuttings of this combination. However, the toothed cut in this case must be at least 1 cm deeper in order for its cut plane to be below the cut plane of the frontal cut. The fastening bolt should run parallel to the frontal part of the notch approximately halfway between the bisector and the top of the sharp corner of the joint.
Rice. 12. Double cut
Cutting depth t v is limited according to DIN 1052. For this, the abutment angle (a) and the height h of the bar to be cut out (Table 1) are decisive.
In the case of pin and bolt connections wooden beams or boards touching the sides are connected by cylindrical connecting elements, such as rod dowels, bolts with countersunk heads and nuts, ordinary bolts with nuts. These rod dowels and bolts must prevent the timber elements from sliding in the joint plane, also called the shear plane. In this case, forces act perpendicular to the axis of the rod dowel or bolt. The dowels and bolts are bending at the same time. In the jointed timber elements, all efforts are concentrated on the inner surface of the dowel or bolt holes.
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 with rod dowels
In one connection, many shear planes can be located next to each other. According to the number of shear planes, which are connected by the same connecting elements, single-shear, double-shear and multi-shear dowel and bolt connections are distinguished (Fig. 14). According to DIN 1052, one-shear bearing connections with rod dowels must have at least four rod dowels.
Rice. 14. Bolted connections
For bolted connections, bolts with nuts made of steel with a standard diameter 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. The minimum dimensions of these washers are given for the different bolt diameters in DIN 1052 (table 2).
In order to prevent splitting of the timber elements to be connected by rod 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 force, on the direction of the wood grain and on the diameter of the dowel or bolt db and do (fig. 15 and 16). Bearing bolts with nuts must maintain greater distances between themselves and from the loaded end than in the case of rod dowels and bolts with hidden heads. On the other hand, rod dowels or bolts with hidden heads that are close to each other in the direction of the wood grain should be spaced apart relative to the cut line so that the joints do not crack (see Fig. 15).
Rice. 15. Minimum distances in the case of rod dowels and concealed head bolts
Rice. 16. Minimum distances in the case of bearing bolts
Holes for pins and bolts are pre-drilled perpendicular to the shear plane. For this, electric drills with a parallel movement bed are used. For pins when drilling holes in wood, as well as when drilling holes in wood and metal connectors at the same time, the hole diameter must match the diameter of the pin.
Also, the bolt holes should match the bolt diameter well. The hole diameter must not be increased by more than 1 mm compared to the bolt diameter. With bolted connections, it is bad when the bolt sits loosely in the hole. It is also bad if, due to the shrinkage of the wood, the bolt clamp in the hole gradually weakens. In this case, a backlash occurs in the shear plane, which leads to even greater pressure of the bolt rod on the boundary planes of the walls of the holes (Fig. 17). Due to the associated flexibility, bolted connections cannot be applied indefinitely. For simple structures such as sheds and sheds, as well as forests, they can, however, be used. In any case, in the finished structure, the bolts must be tightened repeatedly during operation.
Rice. 17. Backlash when bolted
Dowels are hardwood or metal fasteners that are used together with bolts to connect smooth-jointed wooden elements (fig. 18). They are positioned in such a way that they act evenly on the surface of the elements to be joined. In this case, the transfer of forces is carried out only through the dowels, while the bolts provide a clamping effect in the connection so that the dowels cannot tip over. The slats made of flat or profile steel are also attached to the wooden elements using dowels. To do this, use one-sided dowels or flat steel dowels. Dowels come in various shapes and types.
Rice. 18. Connection of wooden elements using dowels and bolts
When installing dowel joints with pressed dowels, first, holes for bolts are drilled in the connected elements. After that, the wooden elements are separated again and, if necessary, a groove is cut out for the main plate. Depending on the construction technology, the dowel is fully or partially driven into the groove of one of the connected elements using a mallet. For the final clamping of the precisely aligned connection, special clamping bolts with a large washer are used. Connections with many or large press-in dowels are clamped using hydraulic press... When connecting with a large number of dowels, as is the case with a device corner joints in frames made of glued planks, it is more preferable to use round plug-in dowels, as with pressed dowels, the press-in pressure may be too high (Fig. 19).
Rice. 19. Dowel joint in the corner of the frame
Each dowel, as a rule, must correspond to one bolt with 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. Larger or smaller dowels can be used depending on the amount of force acting on the connection. 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 in dowel connections | ||
| Outside diameter d d in mm | Bolt diameter d b in mm | Distance between dowels / distance from the dowel to the end of the element, e db, in mm |
| 50 | M12 | 120 |
| 65 | М16 | 140 |
| 85 | M20 | 170 |
| 95 | M24 | 200 |
| 115 | M24 | 230 |
| The values are valid for the D-type round press-in dowel family. | ||
| Table 4. Drawing symbols for special 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 it is necessary to adhere to certain distances of the dowels between themselves and from the edges of the wooden elements. These minimum distances according to DIN 1052 depend on the type of plug and on its diameter (see table 3).
Bolts with dowel nuts are almost always guided 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 about 1 mm into the wood. For dowel connections, the bolted nuts must be re-tightened a few months after installation in order for their tightening effect to remain even after the wood has shrunk. They talk about a connection with a constant transmission of force.
Bearing dowel (nail) connections have the task of transmitting tensile and compressive forces. With the help of dowel joints, load-bearing parts can be fastened, for example, for freely supported trusses, as well as structures made of boards and beams. Stud connections can be made with single-shear, double-shear and multi-shear. In this case, the size of the nails should correspond to the thickness of the lumber and the depth of driving. In addition, when placing the nails, certain distances between them must be maintained. Holes must be drilled in the bearing dowel joints in advance. The drilled hole should be slightly smaller than the diameter of the nail. Since the wood does not crack so much, the nails can be placed closer to each other in this way. In addition, the bearing capacity of the nail joint will increase and the thickness of the wood can be reduced.
Single shear dowel connections used when compressed and stretched rods from boards or beams must be attached to the beams (Fig. 20). In this case, the nails pass only through one connecting seam. They are loaded there perpendicular to the bore 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 cut plane. In the case of paired connection of plank rods on the planes of the main beam, there are two single-shear dowel joints opposite each other.
Rice. 20. Single shear stud connection
At double shear dowel joints the nails pass through three pieces of wood to be joined (fig. 21). Nails have two shear planes, since they are loaded in both connecting seams with an equally directed force. Therefore, the bearing capacity of a double-shear-loaded nail is twice that of a single-shear one. In order for the double-shear dowel connections to not disperse, half of the nails are hammered on one side, and the other half on the other. Double-shear dowel joints are mainly used if the free-standing trusses consist entirely or predominantly of boards or beams.
Rice. 21. Double shear stud connection
Since thin wooden elements break easily when hammering in nails, 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 minimum thicknessesbut(fig. 22). They depend on the diameter of the nail. With pre-drilled dowel joints, the minimum wood thicknesses can be reduced than with simple nailing, as there is less risk of cracking.
Rice. 22. Minimum thickness and depth of driving
Removing the tip of the nail 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 12d n. However, for certain special nails, a driving depth of 8d n is sufficient due to the higher holding force due to the special profiling. With double shear connections, a driving depth of 8d n is also sufficient. At a shallower driving depth, the bearing capacity of the nails decreases. If the nails have a driving depth of less than half the required depth, then they cannot be taken into account for the transfer of forces.
Fastening of formwork, battens and filly, as well as rafters, battens, etc. acceptable with less than four nails. However, in general, at least four nails are required for each seam or multi-cut nail joint designed to transmit forces.
The uniform arrangement of these nails on the plane of the connection is made using nail marks(fig. 23). So 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, the minimum distances must be observed. They depend on whether the direction of force is parallel or across the fibers. Next, you need to monitor whether the ends of the rods or the edges of the wood will be loaded by the force acting in the joint or not. Since there is a risk of cracking with loaded rod ends or edges, large distances from the edges to the nails must be maintained.
Rice. 23. The minimum distance between nails with a single shear connection
At single shear nail connection vertical or diagonal tensioned bar with nails with a diameter of 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 slightly increased. If the nail holes are pre-drilled, then in most cases smaller distances are required.
At double shear nail connections 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 with a double-shear connection
When making nail connections, nails must be driven vertically into the wood. In this case, the head of the nail should only be slightly pressed into the wood so that the wood fibers at the junction are not damaged. For the same reason, the protruding ends of the nails can only be bent in a special way. This should only happen perpendicular to the fibers. To apply the location of the 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 heads of the nails 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 strips can be divided into three types, namely, joints with embedded or outside lying plates with a thickness of at least 2 mm and connections with embedded plates less than 2 mm thick.
Outside overlays usually have in advance drilled holes(fig. 25). They are applied over the joint of the beams or boards at the end and nailed with the appropriate number of wire or special nails. At embedded linings with a thickness of at least 2 mm nail holes must be drilled simultaneously in the wood elements and in the lining. In this case, the diameter of the holes must correspond to the diameter of the nail. Embedded linings less than 2 mm, of which there may be several at the joint, can be pierced with nails without preliminary drilling (Fig. 26). Such connections may only be made with specially designed spline tools and only with special approval from the authorities.
Rice. 25. Connection by means of a perforated steel plate-lining
Rice. 26. Nail connection with embedded steel linings (Greim)
Nail gussets are used for the rational manufacture of wooden half-timbered trusses from single-row sections of wood (Fig. 27). For this, wooden rods of the same thickness are cut to length, impregnated and fitted exactly to each other.
Rice. 27. Connection with a nail gusset
In this case, 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, press into the wood so that the nails sit in the wood for their entire length. Hammering the nail gusset with a hammer or the like is not permitted.
The fastening with the help of nail gussets creates at the nodal points a connection or joints that are strong in compression, tension and shear without weakening the load-bearing section of the wood. For the transfer of forces, the working area of the connection of the nail gusset is of prime importance (Fig. 28). It corresponds to the contact area of the nail gusset with the wood, with the exception of the edge strip with a minimum width of 10 mm.
Rice. 28. Working area of the connection at the nail gusset
Trusses with connecting rods with gussets are industrially manufactured only by licensed enterprises, delivered ready-made to the construction site and installed there.
