Wooden joints without a single nail. Secrets of making tight joints from wood. Making a corner connection

04.05.2020

Making tight joints from wood

Professional layout with precision tools

Tight joints of wood products start with neat and precise markings. This is especially important if you are making connections by hand and marking lines serve as guides for tools. The accuracy of machining depends on the accurate setting of stops, stops, overhang and inclination of saw blades and cutters. The steps below will help you achieve great results. This does not require unique equipment, but should choose tools that guarantee accuracy and efficiency. Also, get in the habit of observing the following rules when measuring and marking.

Use precise tools. For example, try, if possible, to use an accurate steel ruler instead of a tape measure with a flexible tape in most cases. Good tools cost more, but they will last you a lifetime.
Consistency is the key to success. Use the same measurement tools throughout your project to avoid small inaccuracies that affect the quality of your connections. For example, the 300 mm marks on the two rulers may not match.
The main thing is the result, not the measurements. In most cases, measurements should be avoided when you can use an already finished part with connection elements to mark an adjacent part. For example, having made spikes on the front wall of the box, use them to mark the “dovetails” on the blanks of the side walls.
Apply right tricks markings and the right tools. With good marking and measuring tools, it is easier to achieve the required accuracy.

It is not always possible to accurately align the end of the ruler with the end of the workpiece, so in such a situation it is better, as they say, to sacrifice zero. Align the next ordinal division with the end and mark the size in accordance with it.

To draw a thin line parallel to the edge of the workpiece, use a thickness gauge. Shows the outline of the nest on the post after determining the position of the end of the crossbar

A sharp knife leaves the thinnest line, providing high precision markup. In some cases, the recessed line also becomes the starting position for the chisel.

When you need to measure the thickness of the workpiece and the slot disc or the width of the slot, the electronic caliper will eliminate the error by showing the exact size.

Make sure that the machine stops are set exactly at an angle of 90 °, you can use a steel square

Fine-tuning of machines for precise machining of parts

Machine tools and power tools will provide excellent results only if they are correct setting and adjustments. This page shows the main features of setting up three machines that are essential for most workshops: a saw and planer, as well as milling table. Having prepared them for work, remember the following rules.

First of all, make blanks of the same thickness. Start any project by cutting all pieces to the same thickness. Any differences in thickness make it difficult to obtain accurate joints and necessitate additional adjustments in grinding and sanding.
Reasonable approach. Long boards are inconvenient to process, so it is better to immediately cut them into blanks with a small allowance, which are easier to handle, achieving the necessary accuracy.
Double check the dimensions. The actual thickness of plate and sheet materials, as a rule, differs from the nominal, so a caliper should be used to measure them. Only after that, cut the grooves, tongues and folds of the appropriate width.

Before cutting anything, check that the blade is parallel to the slots in the table, set the cross (corner) stop to 90°, and then set the rip fence parallel to the blade. When ripping, use a pressure comb to hold the workpiece firmly against the rip fence.

Align the rear table with the highest point of the cutting edge path of the knives as shown in the figure on the right. Then, using a checked square, make sure that the rip fence is set exactly at right angles to the back table. For best results, always press the workpiece against the fence when planing. Slowly feed the board onto the rotating cutterhead. When the front end boards will pass above the knives, move the down force forward so that the board is pressed against the back table. For best results, adjust the rear table and rip fence.

Plan to do most of your milling work in multiple passes by setting the fence to the final height or width for the last pass. Fix the position of the router after each change in the overhang of the cutter. When selecting grooves, tongues, folds and other elements of connections, use clamps similar to the clamping comb shown here. It is easy to do it yourself, it does not require a lot of material.

The final fit guarantees success

No matter how many connections you want to make on the machine, after each change in settings, always make test passes and connection samples using offcuts. Adjustment should be continued until a tight assembly of the test joint is achieved, and only then proceed to processing the details of the project. But despite all your efforts, sometimes you can find imperfections in the connections. Chips on the saw table or subtle warping of a previously planed workpiece can ruin the job and make assembly impossible. If the piece is too thick or too wide, resist the temptation to adjust the size with the help of lathes. Precise fitting is best left to hand tools.

Little zenzubel. With its help, it is possible to quickly remove a layer with a thickness of 0.5 mm or more from a wide spike or comb. The low angle zener is especially effective when working across the fibers. The cutting edge protruding from the side allows processing inner corner close to the shoulder of the spike.
Rasp or file. A flat rasp with a coarse cut quickly removes material, but leaves a rougher surface than a planer. A flat file is slower, but it works well for smoothing the surface.
Sandpaper. If you need to remove very little material from a spike or other wide surface, glue a piece of 100 grit sandpaper to a suitable piece of board or cork block. Use self-adhesive sandpaper, or stick with regular sandpaper using spray adhesive or double-sided tape. This method allows you to process only one plane without affecting the adjacent ones, as happens if you just wrap the bar with sandpaper.
Chisel. Blades of various widths will allow you to remove material from any hard-to-reach places. When scraping a flat surface, hold the chisel with the bevel up, pressing its flat front edge against the wood.

When using a rasp, chisel, or any other tool to remove material, take your time and regularly check the result by joining the parts.

Plan your build sequence carefully

You have carefully cut out all the details, achieved tightness in all joints and are now ready to start assembling. But before you open the bottle of glue, be sure to do a trial dry assembly (without glue). When assembling the product, determine in what order it is better to connect the parts, how many clamps are required to tightly compress all the joints, and how best to place the clamps so that there are no distortions.

The assembly of large and complex projects is best divided into several simple steps, instead of fussing around trying to glue all the pieces together in one go. For example, when making a cabinet with paneled sides, first assemble the frames with panels, and then proceed with the main assembly. This approach gives you more time to check all connections and requires fewer clamps. Another way to buy time is to use glue with an extended setting time. For example, the regular yellow Titebond adhesive makes the entire assembly in 15 minutes, while the Titebond Extend variety allows you to align the bonding within 25 minutes.

When installing clamps, make sure that their pressure is on the middle of the joint. An incorrectly installed clamp can deform the parts so that a gap forms between them. Sometimes, despite your best efforts, the connections don't come out neat. An accidentally slipped tool, inattention or unnoticed filings near the stop lead to the fact that the connection is loose or a noticeable gap appears in it.

Assemble the locker in stages, first gluing the small side paneled frames. Then you can pay more attention to each connection. Then proceed to assemble the body

How can a seemingly ruined job be salvaged?

The gap can be covered with a mixture of fast-setting epoxy adhesive with sanding dust from the same wood (the mixture should have the consistency of a thick paste). It is better to use epoxy glue instead of PVA, since the putty is inevitably smeared on the surfaces adjacent to the joint and the epoxy glue hardens without being absorbed into the wood. Excess of such a composition is easy to remove by grinding, so that there are no problems when applying the finish. Use this filling method when it comes first appearance connection, not its strength.

If, during trial assembly, the spike dangles in the socket, such a connection will not be strong. Filling the gaps with glue won't do any good, so don't be lazy to reinforce a piece that's too thin with wood. Cut out two overlays to make the spike a little thicker than required, and glue them on both sides. After drying, re-adjust the spike to the dimensions of the nest.

Turn a disadvantage into a virtue

Sometimes it is better not to hide the traces of repair, but to make them visible. In a too narrow ash thorn, two cuts were made and thin cherry wedges were inserted into them, which tightly pressed the narrow cheeks of the thorn to the edges of the socket. In other cases, such as countersunk joints, small chamfers or roundings along the ribs of the shoulders will make the loose seam less noticeable.

Replace Part

This can happen to any of us. Some mistakes don't make sense to fix for two reasons: (1) if no matter your skill and effort, the unsightly defect remains noticeable, or (2) if it's faster and easier to make a new part to replace the damaged one.

Since ancient times, after mastering the tools of labor, a person began to build a dwelling made of wood. Having gone through evolution, a person continues to improve the construction of his home for thousands of years. Certainly modern technologies simplified construction, gave a wide opportunity for imagination, but basic knowledge about the properties wooden structures pass from generation to generation. Consider ways to connect wooden parts.

Consider the ways of connecting wooden parts that beginner craftsmen face. These are mainly carpentry joints passed down from generation to generation, these skills have been used for more than one century. Before joining wood, we assume that the wood has already been processed and is 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 household buildings, are of several types.

End connection

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 joined 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, they would enter with their sharp end into the base of another part to a depth equal to at least ⅓ of the length of the nail;

Nails should not be located on the same line, and their number should be at least two. That is, one of the nails is displaced from the center line upwards, and the second, on the contrary, downwards;

The thickness of the nails should be such that when they are hammered into the wood, a crack does not appear. Pre-drilling holes will help to avoid cracks in the wood, and the diameter of the drill should be equal to 0.7 of the diameter of the nails;

To receive best quality pre-lubricate the joints, the surfaces to be joined with glue, and it is better to use a moisture-resistant glue, such as epoxy.

Invoice connection

With this method, two parts are superimposed one on top of the other and fastened with nails, screws or bolts. Wooden blanks, with this method of connection, can be placed in one line or shifted at a certain angle relative to each other. In order for the angle of connection of the workpieces to be rigid, it is necessary to fasten the parts with at least four nails or screws in two rows of two pieces in a row.

If you fasten with only two nails, screws or bolts, then they should be placed diagonally. If the nails will have a through exit through both parts, followed by bending of the protruding ends - this connection method will significantly increase strength. The connection to the invoice does not require a high qualification of the master.

Half tree connection

This method is more complex, it requires already certain skills and a more scrupulous approach to work. For such a connection, in both wooden blanks, wood is sampled to a depth equal to half 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 sampling angle on both parts is equal, and the width of both samples strictly corresponds to the width of the part. Under these conditions, the parts fit snugly against each other, and their edges will be placed in the same plane. The connection is fastened with nails, screws or bolts, and glue is still used to enhance strength. If necessary, such a connection may be partial. That is, the end of one of the workpieces is cut at a certain angle, and the corresponding sample is made in the other part. Such a connection is used for angular rallying. Both spikes (samples) in this case are cut at an angle of 45 degrees, and the joint between them is located diagonally.

Splicing to length

Such splicing of bars and beams along the length has its own characteristics.

For vertical supports, splicing is simple.

But it’s a completely different matter when a beam or beam at the splicing point is subject to bending or torsion loads, in which case you can’t get by with simple fastening with nails or screws.

The parts to be joined are cut at an angle (into an oblique overlay) and compressed with bolts. The number of bolts depends on the applied loads, but there must be at least two.

Sometimes additional overlays are installed, for example, metal plates, it is better on both sides, top and bottom, for strength, you can additionally fasten with wire.

Cleat

Such a connection is used when laying the floor or for sheathing boards. To do this, a spike is made in the face of one board, and a groove in the other.

With this splicing, gaps between the boards are excluded, and the sheathing itself acquires beautiful view. Appropriately processed lumber enters the distribution network, where they can be purchased at ready-made.

An example of such materials is a floorboard or lining.

Connector "socket-thorn"

This is one of the most common joints of wooden parts.

Such a connection will provide a strong, rigid and neat rallying.

It goes without saying that it requires certain skills and accuracy in work from the performer.

When making this connection, you need to remember that not high-quality tenon 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 must have the same thickness, but if the thickness is different, then the socket is made in the thicker part, and the spike is made in the second, thinner part. The connection is carried out on glue with additional fastening with nails, screws. When driving a screw, remember that pre-drilling will facilitate this process. It is better to hide the head of the screw, and the pilot hole should be ⅔ of the diameter of the screw and be 6 mm less than its length.

One of the very important conditions is the same humidity of the parts to be joined. If the elements to be joined have different moisture content, then when dried, 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%.

The use of wood to decorate buildings.

Choice of wood.

In carving, to perform large crafts with large elements, they often use wood conifers as the main one. They are available, and the striped texture can be used in ornaments.

As a background for overhead and slotted threads, it is used fir.

The valuable material is cedar, its soft, with a beautiful texture and a pleasant yellow-pink or light pink color of the wood core. The wood is easy to cut, cracks little during shrinkage and is resistant to decay.

Wood pears used for highly artistic carving details, as it is durable and warps little from atmospheric influences.

Poplar, the wood is very soft and light - it is used to make a carved decorative column or background shields for attaching false threads.

It is good to use wood to make chains from round rings. apple trees. This wood is used in small crafts, in applied carvings. In this case, the springy properties of the apple tree are used.

Wood is also used lindens. Very light, well planed, well drilled and polished.

carving from oak difficult to manufacture due to its hardness.

But oak is not afraid of moisture, it does not warp. Products made of natural wood are very beautiful, but they can afford it. Veneering is used to reduce the cost of the product. For example, veneered doors are made, by order of the client, "under the oak". We get beautiful doors, outwardly similar to natural ones, but at a much lower price.

They say about the toughest joiners and carpenters that they are able to build a house without single nail. Japanese artisans, even amateurs, are just one of those.

A few years ago, a young automotive industry worker, enthusiastic, fell into the hands of 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 schemes 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 various ways detachable connections.

The variety of fasteners is really 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 an electric tool.

But even if manual labor doesn't inspire you at all, you'll probably enjoy watching GIFs. The way the details interlock with each other is mesmerizing.

In addition to processing solid pieces of wood, it is often necessary to join wooden details into knots and structures. Connections of elements of wooden structures are called landings. Joints in the construction of wooden parts are defined by five types of fits: tense, tight, sliding, loose and very loose fit.

Knots - these are parts of structures at the junction of parts. Connections of wooden structures are divided into types: end, side, corner T-shaped, cross-shaped, corner L-shaped and box corner connections.

Joiner connections have more than 200 options. Only connections used in practice by joiners and carpenters are considered here.

End connection (building) - the connection of parts along the length, when one element is a continuation of another. Such joints are smooth, jagged with spikes. Additionally, they are fixed with glue, screws, overlays. Horizontal end connections withstand compressive, tensile and bending loads (fig. 1 - 5). Lumber is increased in length, forming vertical and horizontal jagged joints (wedge lock) at the ends (Fig. 6). Such joints do not need to be under pressure during the entire bonding process, since significant frictional forces act here. Gear joints of sawn timber, made by milling, meet the first class of accuracy.

Joints of wooden structures must be made carefully, in accordance with the three accuracy classes. The first class is intended for high quality measuring tools, the second class is for furniture production, and the third is for building parts, agricultural implements and containers. The lateral connection of several boards or battens with an edge is called rallying (Fig. 7). Such connections are used in the construction of floors, gates, carpentry doors, etc. Plank, rack panels are additionally reinforced with crossbars and tips. When sheathing ceilings, walls, the upper boards overlap the lower ones by 1/5 - 1/4 of the width. The outer walls are sheathed with horizontally laid overlapping boards (Fig. 7, g). The upper board overlaps the lower one by 1/5 - 1/4 of the width, which ensures the removal of atmospheric precipitation. The connection of the end of the part with the middle part of the other forms a T-shaped connection of the parts. Such connections have big number options, two of which are shown in Fig. 8. These connections (knitting) are used when pairing the log of ceilings and partitions with the harness of the house. The connection of parts at a right or oblique angle is called a cruciform connection. Such a connection has one or two grooves (Fig. 3.9). Cross-shaped connections are used in the construction of roofs and trusses.

Rice. 1. End connections of the bars, resisting compression: a - with a straight half-wood overlay; b - with an oblique overlay (on the "mustache"); c - with a straight half-wood overlay with a joint in an obtuse angle; g - with an oblique overlay with a joint into a spike.

Rice. 2. End connections of the bars (extension), resisting stretching: a - in a straight overhead lock; b - in an oblique laid on lock; c - with a straight overlay half a tree with a joint in an oblique spike (in a dovetail).

Rice. 3. End connections of beams that resist bending: a - with a straight half-wood overlay with an oblique joint; b - with a straight overlay half a tree with a stepped joint; in - in an oblique laid on lock with wedges and with a joint in a thorn.

Rice. 4. Splicing with a notch reinforced with wedges and bolts.

Rice. 5. End connections of the bars, working in compression: a - end-to-end with a hidden hollowed-out spike; b - end-to-end with a hidden plug-in spike; c - with a straight overlay half a tree (the connection can be reinforced with bolts); mr. straight half-wood overlay with wire fastening; e - with a straight overlay half a tree with fastening with metal clips (clamps); e - with an oblique overlay (on the "mustache") with fastening with metal clips; g - with an oblique overlay and fastening with bolts; h - marking the oblique lining; and - end-to-end with a secret tetrahedral spike.

Rice. Fig. 6. End extensions of the milling scheme for end gluing of workpieces: a - vertical (along the width of the part), toothed (wedge-shaped) connection; b - horizontal (through the thickness of the part), gear (wedge-shaped) connection; c - gear joint milling; g - sawing out a gear connection; e - milling of a gear connection; e - end connection and gluing.

Rice. 7. Rallying boards: a - for a smooth fugue; b - on the plug-in rail; in - in a quarter; d, e, f - into a groove and a crest (with various forms of a groove and a crest); g - overlap; h - with a tip in the groove; and - with a tip in a quarter; to - with overlap.

Rice. 8. T-shaped joints of bars: a - with a hidden oblique spike (in a paw or in a dovetail); b - with a straight stepped overlay.

Rice. 9. Cross connections of bars: a - with a straight overlay half a tree; b - with a direct overlay of incomplete overlap; c - with landing in one nest

The connections of two parts with ends at a right angle are called angular. They have through and non-through spikes, open and in the dark, half-dark overlay, half-tree, etc. (Fig. 10). Corner joints (knitting) are used in window irregular blocks, in greenhouse frame joints, etc. A spike connection in the dark has a spike length of at least half the width of the connected part, and the groove depth is 2–3 mm more than the spike length. This is necessary so that the parts to be joined easily mate with each other, and after gluing, there is room for excess glue in the spike socket. For door frames, an angular tenon connection is used in the dark, and to increase the size of the connected surface, in a semi-darkness. A double or triple tenon increases the strength of the gusset. However, the strength of the connection is determined by the quality of its implementation. AT furniture production a variety of corner box connections are widely used (Fig. 11). Of these, the simplest is an open end-to-end spike connection. Before making such a connection, spikes are marked with an awl at one end of the board according to the drawing. By marking the side parts of the spike with a file with fine teeth, a cut is made. Every second cut of the spike is hollowed out with a chisel. For the accuracy of the connection, they first saw through and gouge out the sockets for the spikes in one piece. It is applied to the end of another part and crushed. Then they saw through, gouge and connect the parts, cleaning the connection with a planer, as shown in fig. eleven.

When connecting the parts to the "mustache" (at an angle of 45 °), the angular knitting is fixed with steel inserts, as shown in fig. 12. At the same time, make sure that one half of the insert or clamp is included in one part, and the other half is in the other. A wedge-shaped steel plate or ring is placed in the milled grooves of the parts to be joined.

The corners of frames and boxes are connected with a direct open through spike connection (Fig. 3.13, a, b, c). With increased quality requirements (the spikes are not visible from the outside), the corner knitting is performed by an oblique blind connection, a groove and a ridge, or an oblique connection to the rail, as shown in fig. 13, d, e, f, g and in fig. fourteen.

A box structure with horizontal or vertical transverse elements (shelves, partitions) is connected using corner T-shaped joints shown in fig. fifteen.

In the connection of the elements of the upper belt wooden trusses corner cuts are used with the lower one. When mating the truss elements at an angle of 45 ° or less, one cut is made in the lower element (puff) (Fig. 16, a), at an angle of more than 45 ° - two cuts (Fig. 16.6). In both cases, the end cut (cut) is perpendicular to the direction of the acting forces.

Additionally, the nodes are fixed with a bolt with a washer and a nut, less often with brackets. The log walls of the house (log house) from horizontally laid logs in the corners are connected with a cut “in the paw”. It can be simple or with an additional spike (shank with a pit). The marking of the cut is performed as follows: the end of the log is hewn into a square, to the length of the side of the square (along the log), so that after processing a cube is obtained. The sides of the cube are divided into 8 equal parts. Then, 4/8 part is removed from one side from below and from above, and the remaining sides are performed, as shown in Fig. 17. Templates are used to speed up the marking and the accuracy of making cuts.

Rice. 10. Corner end connections of blanks at a right angle: a - with a single opening through a spike; b - with a single through hidden spike (in the dark); in-with a single deaf (non-through) thorn in the dark; g - with a single through semi-secret spike (in semi-darkness); d - with a single deaf spike in semi-darkness; e - with a triple open through spike; g - in a straight overlay half a tree; h - in a through dovetail; and - in eyelets with undercutting.

Rice. 11. Box corner joints with straight through spikes: a - sawing tenon grooves; b - marking the spikes with an awl; in - connection of a thorn with a groove; g - processing by a planer of a corner joint.

Rice. 12. Corner end connections at a right angle, reinforced with metal inserts - buttons: a - 8-shaped insert; b- wedge-shaped plate; in rings.

Rice. 13. Box corner joints at a right angle: a - straight open through spikes; b - oblique open through spikes; in - open through dovetail spikes; g - groove on the plug-in rail end-to-end; d - in the groove and crest; e - on plug-in spikes; g - on spikes in a dovetail in semi-darkness.

Rice. 14. Oblique (on the "mustache") box connections at a right angle: a - oblique spikes in the dark; b - oblique connection on a plug-in rail; in - oblique connection on spikes in the dark; g - an oblique connection, reinforced with a trihedral rail on glue.

Rice. 15. Direct and oblique connections of blanks: a - on double connection in oblique groove and comb; b - on a straight groove and comb; in - on a trihedral groove and a crest; g - on a straight groove and a comb in the dark; d - on straight through spikes; e - on round plug-in spikes in the dark; g - on a spike in a dovetail; h - on the groove and the crest, reinforced with nails.

Rice. 16. Nodes in farm elements.

Rice. 17. Conjugation of the logs of the walls of the log house: a - a simple paw; b - a paw with a wind spike; c - paw markings; 1 - wind spike (pit)

Connections of wooden elements have the task of connecting mating Construction Materials, such as edged 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 on branches and crosshairs, are distinguished. Spatial sheet steel connectors and pre-drilled steel sheet escutcheons often replace carpentry connections.

Connections that must transmit forces of a certain magnitude and direction, such as compressive forces, are also called joints of connected wooden elements like rods, for example, compressed rods. Compressed rods connected at an acute angle can be connected at notches. Other connections of wooden structures are arranged at the expense of joints of wooden elements using connecting means.

According to the type of connecting means, such connections are called nail or bolt, dowel or dowel connections. In wood construction, glued building construction. Since they have particular advantages, the use of glued timber structures is of increasing importance.

Longitudinal connections

There are longitudinal connections on the supports and longitudinal connections in the span. Above the supports, perpendicular trunnions are used, a joint “in the paw” and a partially trunnion joint “in the paw” (Fig. 1). To reinforce these joints, building brackets made of flat or round steel can be driven in from above or from the side. Often, wooden elements are joined head-on and fixed only with building brackets. If, however, large tensile forces act at the joint, for example, at the girders on the roof rafters, then both elements are joined head-on on the support and connected by side plates made of boards or perforated strips of steel protected from corrosion.

Rice. 1. Longitudinal connections

Runs can also be made in the form cantilever-suspended(Gerber runs) or hinged girders. They have a joint located in a 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 runs are connected with a straight or oblique overlay. The incoming purlin is held in place by a screw bolt, also called a pivot bolt. The swivel bolt with washers must bear the load from the suspended purlin.

Rice. 2. Longitudinal joints of Gerber girders

Gerber purlins with a seam lying on top are impractical, since there is a danger that the purlins at the edge of the seam will come off. With a suspended joint, having screwed up, there is no danger of separation.

To connect the 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 front butted ends of the runs (see Fig. 2).

Corner connections

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 cut-out trunnions, a smooth angular foot and a compressed foot (Fig. 3). With the help of cut-out trunnions and smooth corner legs, the ends of thresholds, girders and rafter legs lying on supports or protruding cantilevered are connected. Nails or screw bolts can be used to secure the joints. The compressed paw has planes obliquely entering each other. It is particularly suitable for connecting loaded, fully supported thresholds.

Rice. 3. Corner joints

Branches

When branching, a beam suitable at a right or oblique angle in most cases is superficially joined to another beam. In normal cases, a joint on the trunnions is used, and in secondary structures, the joint "in the paw" 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 timber. 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 a large area of the remaining section of the bars.

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 bars in the connection do not fit at right angles to each other, for example, at the corner struts, then the trunnion at the strut must be made at right angles to the horizontal (or vertical) structural element (see Fig. 4).

Rice. 4. Pin connections

When installing trunnions in wooden beams and runs, the trunnion must bear the entire load. It is more advantageous to make such connections using beam shoes from corrosion-protected steel (Fig. 9). These shoes are fixed with special nails in such a way as to prevent them from buckling and turning relative to the joint. Besides, transverse section beams are not weakened by pin holes.

Cross connections

Wooden beams can intersect in the same plane or with offset planes and be overhead or support. Bars intersecting in the same plane can intersect "IN THE LAPU" if the weakening of the section does not play any role (Fig. 5). It is advisable to tie the intersecting overhead thresholds on the support beams with round dowels (pins) made of hard wood or steel 10 to 12 cm long (Fig. 6).

Rice. 5. Connection "in the paw"

Rice. 6. Connection with round dowels (pins)

The beams joining on the side receive good support on the pole if their connection is made “In the groove” (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 an immovable connection, 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 cutout is made in the rafter leg corresponding to the slope, which is called sidebar(Fig. 8).

Rice. 8. Insert rafter leg

The depth of the tie-in in the rafter legs with 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

cuts

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. According to the number and position of the force-transmitting planes, a frontal cut, a cut with a tooth, and a double front cut with a tooth are distinguished.

At frontal cutting(also called a frontal stop), the receiving beam has a wedge-shaped cutout that matches the shape of the end of the compressed rod (Fig. 10). The frontal plane must pass at an angle dividing the obtuse outer corner notches in half. The fastening bolt must also have the same direction, guaranteeing the joint from lateral displacement. To mark the cut, parallels are drawn at the same distance from the sides of the corner, 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 cutting

Under the action of a compressive force, the wood lying in front of the frontal part of the compressed rod works on slice(see fig. 10). Since the permissible stress on the cut of wood along the fibers is relatively small (0.9 MN / m 2), the plane of the wood in front of the cut edge (cut plane) must be large enough. Since, in addition, cracking due to shrinkage should be taken into account, with rare exceptions, the length of the cut plane should not be less than 20 cm.

At reverse or notched cut the cutting plane is cut at a right angle to the lower side of the compressed rod (Fig. 11). Due to the fact that due to an eccentric connection in a notched notch there may be a risk of splitting the compressed rod, it is necessary that the free end of the notch does not fit tightly 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 cutting planes is similar to that used for each of the cuttings of this combination. However, the notched cut in this case must be at least 1 cm deeper so that its cut plane is below the cut plane of the frontal cut. The fastening bolt should run parallel to the front of the notch approximately midway between the bisector and the top of the acute joint angle.

Rice. 12. Double notch

Cutting depth t v is limited according to DIN 1052. The decisive factors for this are the contact angle (a) and the height h of the cut rod (Table 1).

Pin and bolt connections

In the case of pin and bolt connections, wooden beams or boards that are in contact with 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 should prevent the wooden elements from moving in the connection plane, which is also called the shear plane. In this case, forces act perpendicular to the axis of the rod dowel or bolt. Dowels and bolts at the same time work on bending. In the connected wooden elements, all efforts are concentrated on the inner surface of the 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 with rod dowels

In one connection, many shear planes can be located next to each other. According to the number of cut planes that are connected by the same connecting elements, single-cut, double-cut and multi-cut dowel and bolted connections are distinguished (Fig. 14). According to DIN 1052, single shear load-bearing connections with dowel pins must have at least four dowel pins.

Rice. 14. Bolted connections

For bolted connections, mainly bolts with nuts made of steel with a normalized diameter of 12, 16, 20 and 24 mm are used. In order to prevent the head and nut of the bolt from cutting into the tree, strong steel washers should be placed under them. The minimum dimensions of these washers are given for various bolt diameters in DIN 1052 (Table 2).

In order to prevent splitting of the wooden elements to be connected by rod dowels and bolts, these connecting means must have 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 fibers and on the diameter of the dowel or bolt db and do (fig. 15 and 16). For load-bearing bolts with nuts, greater distances must be maintained 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 located close to each other in the direction of the wood fibers should be spaced apart from the cut line so that the joints do not crack (see Fig. 15).

Rice. 15. Minimum distances in case of rod dowels and hidden head bolts

Rice. 16. Minimum distances in case of bearing bolts

Holes for pins and bolts are pre-drilled perpendicular to the cutting plane. For this, electric drills with a bed with parallel movement are used. For pins when drilling holes in wood, as well as when drilling holes in wood and metal connecting elements, the diameter of the hole must correspond to the diameter of the pin.

Also, the bolt holes should match the diameter of the bolts well. Do not increase the diameter of the hole in comparison with the diameter of the bolt by more than 1 mm. With bolted connections, it is bad when the bolt sits freely in the hole. It is also bad if, due to the shrinkage of the wood, the clamp of the bolt in the hole gradually weakens. In this case, a play appears in the shear plane, which leads to even greater pressure of the bolt shaft on the boundary planes of the hole walls (Fig. 17). Due to the flexibility associated with this, 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 when bolted

Dowel connections

Dowels are fasteners made of hard wood or metal, which are used together with bolts to connect smoothly joined wooden elements (Fig. 18). They are positioned in such a way that they evenly act on the surface of the elements to be joined. In this case, the transmission of forces is carried out only through the dowels, while the bolts provide a clamping action in the connection so that the dowels cannot tip over. Laths made of flat or profiled steel are also attached to wooden elements using dowels. For this, one-sided dowels or flat steel dowels are used. Dowels come in various shapes and types.

Rice. 18. Connecting wooden elements with dowels and bolts

When making dowel connections with pressed dowels, bolt holes are first drilled in the elements to be connected. After that, the wooden elements are separated again, and, if necessary, a groove for the main plate is cut. Depending on the construction technology, the dowel is completely or partially driven into the groove of one of the connected elements using a mallet. For the final clamping of an axially aligned connection, special clamping bolts with a large washer are used. Connections with many or large pressed-in dowels are clamped with hydraulic press. For connections with a large number of dowels, as is the case when making corner joints in frames made of glued plank elements, it is more preferable to use round plug-in dowels, since the pressing pressure may be too high with pressed dowels (Fig. 19).

Rice. 19. Dowel connection in the corner of the frame

Each dowel, as a rule, should 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. Depending on the magnitude of the force acting on the connection, larger or smaller dowels can be used. The most common are diameters 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
Outer diameter d d in mm	Bolt diameter d b in mm	Distance between dowels/distance from dowel to element end, 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 push-in dowels type D.

Table 4. Drawing symbols for special type 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 dowel placement 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, they depend on the type of dowel and its diameter (see table. 3).

Bolts with dowel nuts are almost always driven 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. With dowel connections, the nuts on the bolts must be re-tightened after a few months after installation, so that their tightening effect remains even after the shrinkage of the wood. They talk about a connection with a constant transmission of force.

Bearing pin connections

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. Nail joints can be made 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 the drive. In addition, when arranging the nails, certain distances between them must be maintained. In load-bearing dowel joints, holes must be drilled in advance. The drilled hole should be slightly smaller in diameter than the diameter of the nail. Since the wood does not crack as much, the nails can be placed closer together in this way. In addition, the load-bearing capacity of the nail joint will increase and the thickness of the wood can be reduced.

Single shear dowel joints 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 shaft of the hole and can bend with too much force. Since shear forces also occur in the connecting seam in the body of the nail, this sectional plane is called the shear plane. In the case of paired joining of plank rods on the planes of the main beam, there are two single-cut dowel joints opposite each other.

Rice. 20. Single shear dowel connection

At double shear dowel joints the nails pass through three connected wooden elements (Fig. 21). Nails have two cut planes, since they are loaded in both connecting seams with the same directed force. Therefore, the bearing capacity of a double-shear loaded nail is twice that of a single-shear nail. In order for the double-cut dowel joints to not disperse, half of the nails are hammered on one side, and the other half on the other. Double-cut dowel joints are mainly used if freely supported trusses consist entirely or mainly of boards or beams.

Rice. 21. Double-cut dowel connection

Minimum timber thicknesses and minimum nailing depth

Since thin wooden elements easily split when hammering 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 thicknessesa(Fig. 22). They depend on the diameter of the nail. With pre-drilled nail joints, the minimum thicknesses of the wood can be less than with simple nailing, as there is less risk of cracking.

Rice. 22. Minimum thickness and depth of driving

The distance of 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, 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 8d n is also sufficient. With a shallower driving depth, the bearing capacity of the nails decreases. If the nails have a driving depth of less than half that required, then they cannot be taken into account for the transmission of forces.

Minimum spacing between nails

Fixing formwork, battens and fillets, 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-shear nail joint intended to transmit forces.

The uniform arrangement of these nails on the plane of the connection is made using nail marks(Fig. 23). In order for two nails located one after another not to sit on the same fiber, they are displaced relative to the point of intersection of mutually perpendicular nail lines by the thickness of the nail in both directions. In addition, minimum distances must be observed. They depend on whether the direction of the force is parallel or across the fibers. Further, it is necessary to monitor whether the ends of the rods or the edges of the wood are loaded by the force acting in the joint 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 with a single shear connection

At single shear nail connection vertical or diagonal tensioned rod with nails with a diameter of d n ≤ 4.2 mm, the minimum distances shown in fig. 23. When using nails with a diameter of d n> 4.2 mm, these distances should be slightly increased. If the nail holes are pre-drilled, in most cases smaller distances are required.

At double-cut nail connections nails are arranged in ledges. Between the risks of a single-cut nail joint, additional risks are drawn with a minimum distance of 10d n (Fig. 24).

Rice. 24. Minimum distances between nails for double-cut joint

Nail connection device

When making nail joints, 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 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. For drawing the location of the nails, as a rule, suitably drilled templates made of thin plywood or tin are used. In the case of plywood templates, holes are made of such a diameter that nail heads can pass through them. In the case of tin templates, the locations of the nails are marked with a brush and paint.

Nail connections with steel plates

Nail joints with steel plates can be divided into three types, namely, connections with embedded or externally laid plates with a thickness of at least 2 mm and connections with embedded plates with a thickness of less than 2 mm.

Overlays on the outside, as a rule, have in advance drilled holes(Fig. 25). They are superimposed over the connection of beams or boards to the butt and nailed with the appropriate number of wire or special nails. At embedded overlays with a thickness of at least 2 mm holes for nails must be drilled simultaneously in the wooden elements and in the overlays. 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 junction, can be pierced with nails without pre-drilling (Fig. 26). Such connections may only be made with specially designed spline tools and only on the basis of special approval from the authorities.

Rice. 25. Connection with a perforated steel plate-lining

Rice. 26. Nail connection with embedded steel plates (Grame)

Connections with nail gussets

Nail gussets are used for the rational manufacture of wooden half-timbered trusses from single-row sections of wood (Fig. 27). To do this, wooden rods of the same thickness are cut to length, impregnated and adjusted 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 and edges.

Nail gussets must be placed symmetrically on both sides and, using a suitable press, pressed into the wood so that the nails sit in the wood for their entire length. Hammering of nail gussets with a hammer or the like is unacceptable.

Fastening with the help of 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 working area of \u200b\u200bthe connection of the nail gusset is of primary importance (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 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 mounted there.