How to make end grooves for connection. Encyclopedia of technologies and techniques - attachments for the router for making grooves and tenons
For a long time, a tongue-and-groove connection has been used in carpentry and carpentry. Ancient architects, using this method, managed to create unique wooden buildings without single nail or a screw. And although a wide variety of hardware is now quite accessible, the articulation individual parts various designs this method not only has not lost its relevance, but also finds wide application in modern products and materials.
The principle of connection and its varieties
In terms of design, all tongue-and-groove joints are made according to the same principle: a protrusion is made on one part, and a recess is made on the second. They are exactly the same in configuration and size. When these two parts are tightly joined, a strong technological unit is obtained. When building houses, such a connection prevents the shift of one part of the structure relative to another; when making furniture, it significantly increases the area on which glue is applied, thereby providing additional strength to the product.
Based on the geometric shape of the protrusion and recess, such joints are divided into two main types:
- rectangular cross-section (sometimes with rounded edges of tenons and grooves);
- in the form of a trapezoid (also called “ dovetail»).
Based on the number of spikes and recesses that need to be made for one joint of parts, these connections are divided into:
- single-spike;
- multi-spike.
Important! Regardless of the number and geometric shape of the protrusions and recesses, they must be made only parallel to the grain of the wood.
Scope of application
The tongue-and-groove connection has found application in many areas of our everyday life. For example, when arranging the floors of premises according to this principle, such familiar coatings as laminate, ordinary batten, chipboard, fiberboard or MDF boards.
Wood is one of the most environmentally friendly safe materials, are used for the manufacture of a wide variety of furniture (from a simple kitchen stool to a designer set for a living room or dining room), roller plate curtains, blinds and much more. And all these products are mainly made using a tongue-and-groove connection.
During the construction of wooden frame buildings, houses made of timber, when arranging the beam-rafter structure of the ceiling and roof, one also cannot do without arranging protrusions and recesses.
Beam connection
The tenon and groove in the beam connection is used both for arranging corner structures made of wood, and for longitudinal alignment of individual pieces. Depending on the cross-sectional dimensions and expected loads, the geometry and number of protrusions and lugs are selected. For example, during construction wooden houses Mostly a single-pin connection is used. And to increase the length of small-section bars using glue, a multi-tenon method is used.
Connecting boards
Almost all owners of suburban real estate have long fallen in love with such a material as lining, as a result of which they obtain an absolutely flat vertical surface. The tongue and groove connection of boards is used for arranging floors, interior decoration at home, and also for outer skin buildings (with an antiseptic coating, of course).
The protrusions are tightly fixed in the recesses of adjacent boards, which prevents them from moving relative to each other. When arranging floors, the tight connection of tongue and groove boards with each other prevents them from moving in the vertical plane (the floor is level) and significantly increases the heat-saving properties of the coating (there are simply no gaps between the boards).
Using a manual electric router
Arrangement of tenon joints minimizes labor costs and significantly reduces the time for carpentry work. Of course this one useful tool will not help when building a house, for example, from timber with a cross-section of 150 x 150 mm, since there are no cutters of this size for a manual router, and the power of this unit will not be enough to install them. But if you want to build furniture yourself, small or door frames, then such a tool is simply necessary. Depending on the size of the parts to be joined and the geometric configuration of the connection, you purchase the necessary cutter, or maybe two (one for cutting the groove, the other for making a tenon). The milling tool's adjustment devices, as well as guide bearings (usually included with these cutters), will help create projections and recesses that match exactly in size and shape.
DIY tools and accessories
If you need to make some kind of piece wooden product, then it is not economically profitable to purchase an expensive electric router. Most likely, everyone on the farm has necessary set tools, and if you have to buy more, then very few. In addition, additionally purchased devices may be useful in the future for the production of small repair work(for example, repairs wooden furniture). In order to make a tenon-groove connection with your own hands using only ordinary hand tools, you will need:
- wood hacksaw (fine teeth);
- carpentry thicknesser ( special device for marking) or a regular construction square;
- ruler and pencil;
- wood chisel.
Making your own corner joint
As an example, let's look at how to make a tongue-and-groove connection between two bars of the same cross-section at right angles using available tools. Let's say you need to connect 60 x 60 mm (they may well be suitable for making window frames summer house).
The thickness of the protrusion for a single-tenon connection (in accordance with the recommendations of handbooks on carpentry) should be ⅓÷⅜ of the thickness of the block (in your case it will be 20 mm). The length of the tenon will be equal to the thickness of the block (60 mm). The dimensions of the recess must correspond to the dimensions of the tenon, so that it fits into the eye with force.
Attention! Spikes must be installed on vertical parts wooden structure, and the grooves are horizontal.
The algorithm for performing the work is quite simple:
- First, we mark the future protrusions and eyes. If you do not pay due attention to this process, the manufactured tenons and grooves may not match each other in size or relative position. There is also a danger that they will not fit into each other tightly. All this will significantly reduce the strength and reliability of the connection.
- Using a thicknesser (or square) at a distance of 60 mm from the end, draw a line on all four sides of both bars.
- Then on two opposite sides and at the end we draw two parallel lines at a distance of 20 mm from each other.
- Using a hacksaw, we make cuts along the marking lines to the transverse line, that is, to a depth of 60 mm.
Note! To ensure that the thickness of the cut (approximately equal to the setting of the teeth of the cutting blade of the hacksaw) does not affect the accuracy of the joint, we install the saw blade on the outside (when making a tenon) or on the inside (when making a groove).
- At the end of the block with a protrusion, we saw off the outer pieces of wood.
- Using a chisel, carefully hollow out the inside of the recess.
- We insert the tenon into the groove and check the made connection. If necessary, remove protruding defects with a chisel.
In conclusion
If you need to arrange a tenon and groove yourself, it is best to practice on scraps of bars.
If the manufactured protrusions and recesses coincide exactly, and the articulation of the individual parts is strong, then you can begin work on the prepared building material. Well, if the tenon fits into the groove too freely, or vice versa, then you need to once again check the correctness of the markings, conduct another training session, and only after that proceed with the implementation of the planned project.
Dovetail, detachable tenon joint (trapezoidal grooves), used in mechanical engineering and carpentry for reliable fastening of parts to each other. In this material we will consider the manufacture of devices that facilitate the production of grooves in wood using a hand router.
DIY accessories for a wood router
The machine itself is a very ancient invention of mankind; descriptions of the principles of milling appeared in the 16th century, and the prototype of the machine was the invention of Leonardo da Vinci, who proposed rotating a round file to increase the processing of the product, which can be considered the first analogue of a milling cutter.
And already the American inventor Eli Whitney, over the years of his life from 1765 to 1825, brought to fruition all the scattered attempts to create a full-fledged machine, for which he is rightfully considered the creator of the first milling machine, although not all scientists agree with this statement.
And since the machine has such ancient roots, there are a great many adaptations for the manufacture of various parts; describe them all in the light of this material is not possible, and therefore we will consider only some of them, in my opinion, the most important and useful.
Universal device for tongue and groove connection
factory plate for making a tongue and groove connection
Used with a router to cut the corresponding grooves and tenons, it is installed in a vice and the part is pressed against the device with a clamp. Typically sold in stores.
appearance connections
Consider devices for milling grooves
Cut it out top part– a tabletop made of 18 mm plywood, 40 cm long and sufficiently wide to handle the thickest workpiece that you plan to join with a tenon.
Cut two 5x10 cm bars, sawing them to the same length as the top. The bars will subsequently play the role of pressing the workpiece and centering it relative to the groove in the tabletop. To prepare the top, draw a line down the center of the top, then rout a mortise along the line at one end.
schematic representation of equipment
Please note
The notch should be the same width as the copy ring you will use with your router bit. The notch should be long enough to match the length of the longest groove you will be cutting.
Then mill two adjustment slots perpendicular to the center line. Finally, drill an inspection hole between these two slots. To assemble the entire structure, screw the bolts into the jaws and secure the top to the bars with wing nuts and washers.
To use our equipment, draw a groove on the workpiece and mark the center line on it. Loosen the screws and place the workpieces between the bars so that the center line connects with the top line of the jig, making sure that the edge of the workpiece is opposite the edge of the top.
Pinch the lambs. Align the router bit to one end of the mortise drawing, then mark guide lines on the top surface of the table along the edge of the router base.
How to work correctly with tongue and groove equipment
Repeat this again to mark the lines of the other end. Route the slot by starting the cut at the bottom by aligning the router base with the first construction line, and stop routing when the insert reaches the second construction line.
There are many types of different connections that are widely used in repairs today. They are needed for assembling and repairing furniture, for connecting individual parts of some functional elements. But it is the tenon joint that has earned the greatest popularity among all types.
A tenon joint is a connection wooden parts by tightly fitting the tenons into the holes (grooves).
The connection based on grooves and tenons is mainly used for wooden materials. It provides a fairly strong joining, while preventing the parts from deforming. This is especially good for furniture, when it is necessary to ensure maximum reliability of fasteners.
Anyone can make a tenon joint, but before serious assembly you need to practice properly if you do not have any carpentry skills. As a result, you can get a fairly high-quality fixation. And if you further fasten it metal corners, then the strength of your furniture is at a high level.
Manufacturing of dovetail tenon and mortise.
There are many ways in which a tenon joint can be made. But before considering the main most common ones, it is advisable to take into account some rules and subtleties that will definitely need to be followed while performing the work:
- If you have the opportunity, make the tenon using special precision equipment. This will ensure that the sizes of the tenons and grooves match each other as closely as possible. Such equipment is available in every carpentry shop or industrial labor training room.
- It happens that you are going to make furniture that does not require much precision. Then you can make the connections yourself. To do this, the tenons must be cut exclusively along the grain of the wood. In this case, the width should be approximately 17-20 times the thickness of the main part. This way you can avoid chipping and cracking.
- Things are a little simpler when cutting tenons on plywood. IN in this case The thickness of the spinal sinus can be absolutely any. The width of the main parts does not affect this. But the principle of matching in the direction of the fiber remains the same.
- After the tenons have been cut out and their size has been checked, the wood must be slightly dried. This refers to the usual keeping of the material indoors throughout the day. This way the wood can accept permanent form, which will help avoid bending of the connection in the future.
Preparation of the instrument and the first part of the measurements
Measuring straight tenon joints.
Now let’s look at the main and most common option for how you can make a high-quality tenon joint with your own hands. It is based on the use of a regular file or a large saw (depending on the required dimensions).
So, the first thing you need to do is choose a tool. It is important to keep in mind that each file has its own cutting width. Therefore, in the end, part of the tenon will become slightly larger. And how much depends directly on this width. That is why, when measuring connection parameters, take into account the width of the cut.
Now start marking. For this you will need a pencil and a ruler. First measure the parts that need to be connected to each other. After this, the width of the parts is applied at the site of the future cut. In this case, the depth of the cut itself will be exactly equal to the thickness of the main part.
Typically, many furniture designs may require multiple tenons or mortises on one piece. In this case, you need to focus on how similar they will be. If they are identical, then it is enough to take one measurement. At different sizes produced required quantity measurements Also remember the rule: it is advisable to make cuts a little smaller in thick parts, and deeper in thin ones.
Marking of the second part
Tenon joint elements.
After this, we move on to marking the second part of the connection. To do this, you need to take the two parts that are supposed to be connected and attach them tightly to each other. In this case, you need to ensure that it matches the lines of the cuts. When the parts are perfectly attached to each other, it is recommended to clamp them in a vice so that they do not move.
Now that the parts are properly fastened, you need to apply marks with a pencil on the second part that has not yet been marked, and then make the initial cuts with a file. These will not be solid lines, but just thin marks, similar to scratches. But it is still necessary to do them, since it will be easier to work later. Only when making marks, try to do it in such a way as to achieve perfect evenness and avoid bending.
After this, it is necessary to release the parts and move them further relative to each other. It is important to take this into account. If you move the parts just a little by the width of the file, the connection will turn out to be quite rigid. And if you make the shifts a little more, it will be freer.
However, it cannot be said that any of the options is bad. It all depends on the nature and size of the parts being connected. And also on the specific type of wood used. If you use plywood, then you can make shifts only along the width of the cut, since in any case it will not be subject to severe deformation.
Final formation of tenon joints
Methods for tenoning wooden parts.
When all this is done, we move on to the thorough formation of the tenons and grooves. In order for everything to go correctly, you need to constantly take measurements during work in order to eliminate, if possible, the risk of error. Be especially careful about the straightness of the lines. For large parts use a building level for control.
So, the main part of the work is finished: tenon joints formed. Now you need to finally measure everything to make sure it is correct, after which you can move on to the final design. For this you can use sandpaper or manual jigsaw. It depends on how rough the surface is.
Connection will follow. It is important to consider the type of connection here. They are detachable and non-detachable. Permanent connections should be stronger and more thorough, and detachable connections should be such that they can be disassembled if the need arises. For permanent connections, glue is used, and for detachable connections, the corners must be slightly rounded.
The option of how you can make tenon joints with your own hands has been considered.
There are several more methods, but they are more complex and more suitable for professionals. But if you don’t rush anywhere, you can gradually acquire skills and perform subsequent work simply.
Good afternoon, friends!
Today let's look at one of the ways to make a classic carpentry connection tenon - groove. We will not just make the connection on its own, but we will make a full-fledged product - a small decorative table. We will have the opportunity to practice, because such a product requires 8 connections of the drawers to the legs at once. Along the way, let's look at some other techniques for working with manual router.
To make a tenon-groove joint, we start by cutting out the groove using a hand router. To do this, we will need a router with a rip fence and a straight groove cutter. IN in this example grooves are selected on the table legs at the junction with the drawers. In the photographs you see an example of making table legs from purchased balusters - this is how the table looks very impressive. However, if desired, you can also use a regular wooden block.
We mark the location of the future groove as follows: we find the center of the workpiece, because we want the groove to be exactly in the middle (in this case, the thickness of the block is 50mm, respectively, the center is 25mm). We mark the boundaries of the future groove. A board 100mm wide will be used as a drawer; accordingly, we will make a 90mm groove. After marking, install the router with a parallel stop so that the center of the cutter is located exactly along center line and start cutting out the groove.
To reduce the load on the cutter, it is better to carry out the sampling gradually - in several passes, each time lowering the cutter lower and lower. In this case, the groove depth was 20mm, sampling was carried out in 4 passes with a step of 5mm. As you can see in the photo, on the first workpiece, I was not able to accurately observe the milling boundaries and the groove turned out to be a little larger than necessary. In this case, this is not a problem - the groove will still be completely covered by the drawer, but you should be careful and try to follow the markings. Without changing the router settings, we make the same grooves on all workpieces.
To avoid such a defect, pads are often pressed against the workpiece, which physically do not allow the router to go further the right place, but in this case, since the groove is selected too close to the edge of the workpiece, it is not possible to use this method and you have to rely only on your own strength. If you often plan to make a tongue-and-groove joint, you should think about making a template that will allow accurately make grooves close to the edges of the workpieces. You should also be careful with the possible displacement of the cutter in the lateral direction - always press firmly rip fence to the workpiece.
Next, we proceed to making the spike. I had at my disposal circular saw, with the help of which there is nothing complicated about this. We take the blanks for the drawers, set them on the saw to 20mm - the height of the future tenon, and raise the saw blade above the table to a distance equal to half the thickness of the groove. In this case, a cutter with a thickness of 15 mm was used, respectively, we extend the saw blade by 7-8 mm.
Thus, without changing the saw settings, we process all 4 workpieces for the drawers on both sides. Then, if necessary, change the height saw blade, and in the same way we process them from the ends to obtain a full-fledged tenon.
All that remains is to slightly round the corners of the tenon with a knife to ensure an exact match with the groove and the connection is ready!
After cutting the legs to size, you can proceed to gluing the legs and drawers.
All we have to do is make the tabletop. In this case, it was cut with a router from 30mm thick glued board. For more details on how this was done, see In principle, the tabletop can be of any shape.
The edge of the table top was then finished with an edge moulder. And glued to the dowels to the drawers.
The table is ready! Agree, thanks to the baluster legs it looks very impressive.
In the coming days, stay tuned for another post on techniques for working with a hand router. It will be interesting!
Good luck to everyone in the craft!
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So, in what cases is a tongue-and-groove connection needed?
Vertical jumpers
In most products (for example, tables), jumpers or spacers are connected to the vertical legs (Fig. 1). With this arrangement, the fibers on the bonded surfaces of the parts are mutually perpendicular.
Horizontal jumpers
The situation with jumpers, for example, on a wall table. how to do it, which we will tell you in one of the following articles, is somewhat different. To create drawer compartments, the lintels are installed horizontally relative to the legs, and instead of one wide tenon with a large glue surface, you have two small glue surfaces.
Solution
To solve this problem, you will have to cut out two grooves and two tenons (Fig. 2). This may look like a loose connection, but it's not entirely true. Double spikes increase the gluing area due to two large cheeks.
So, making a double groove tenon connection - good option connecting the legs with narrow (thin) jumpers, but at the same time the number of cuts doubles. This does not mean that the number of machine settings is doubled.
In the wall table (about it in the next article) the jumpers and legs are of the same thickness. This means that the outer cheeks of the tenons (and grooves) can be at the same distance from the edges of the part.
Therefore, two grooves on each leg (and two outer tenon cheeks) can be cut with one machine setting.
As with any mortise/tenon joint, the mortises must first be selected (Figures 3 and 4). They only require one installation to drill them out. drilling machine. Then the ends of the grooves can be straightened with a chisel.
How to make double spikes
External cheeks
First, to cut out the shoulder, install a longitudinal ruler, which will serve as a limiter (Fig. 5-7), determining the length of the tenon. Then lift the disc and cut out the first cheek using overlapping cuts. Then unfold the part and cut out the second cheek. Check fit and. if necessary, lift the disk.
Inner cheeks
Mark them directly along the grooves. To do this, place the part above the grooves and make the appropriate marks (photo 2). As with the outer cheeks, sawing out the inner cheeks requires only one blade setting. But this time the part must be placed on its end (Fig. 8-13).
Then, use a sharp chisel to trim the tenons to the grooves.
Double tongue-and-groove connection - how to make: instructions for photo
1. To create an opening for drawers, install two instead of one lintel. But then the gluing surface on the spikes will decrease.
2. When using double tongues and grooves, the gluing area doubles, which increases the strength of the connection between the parts.
3. To determine the length of the grooves, mark the top and bottom ends of each piece. Then, to determine the width of the grooves, mark all of their sides.
10. Without changing the disk settings, rotate the part so that the opposite edge of the part is pressed against the limiter block. Saw out the cheek and remove excess wood.
11. Having roughly cut out the tenons, check their fit to the grooves. For an accurate fit, the cheeks and shoulders will have to be trimmed with a chisel.
12. If the tenons do not fit exactly into the grooves, several passes of a sharp chisel should remove the unevenness on external sides cheeks.
13. In order for the tenons to fit completely into the grooves, their shoulders must be trimmed, while the inner shoulder may be slightly recessed.
Different types of carpentry joints - which are stronger than others
Do you need a frame connection that won't fall apart when the kids turn the cabinet door into a playground for their fun?
Or a box connection that can withstand jerks and shocks without damage?
We tested 12 samples of both types to choose the two best.
Previously, we put a variety of mortise, tenon, butt and tongue joints to the rigors of testing to find out which ones were the best. Now, to find out which frame and box joints are the strongest, we made dozens of test specimens and pushed them to their death (literally).
For the door frames, we made six samples each with counter-profile joints, tongue-and-groove, half-timber and semi-hidden tenons.
We also produced prototypes of box joints:
- with tongue and groove,
- with straight box tenons,
- with open and semi-concealed dovetail spikes,
- keyed with dovetail groove,
- tongue-and-groove with two shoulders,
- in a fold and a mustache with a lock.
To ensure equal conditions, all joints were made from wood of approximately the same density using the same glue. In the frame joint samples (with the exception of certain specified cases), red oak with a cross-section of 18x50 mm was used. Samples of box joints are made of poplar 12×100 mm.
On testing equipment into each connection in two ways. The first measured the tensile strength of connections, as in the case of rough opening drawer or a sharp side jerk of the sliding door.
Another test tested the ability of joints to resist fracture before the parts became out of square and the bond failed. (Imagine a child swinging on a closet door, or a wide linen drawer tilted from a sharp tug.)
When the cracking and crunching of the breaking wood subsided, we found that all joints withstood significantly greater tensile loads than fracture loads, which seemed quite unusual for real-world conditions. For example, box joints withstood on average a tensile force of about 675 kgf, and a breaking force of only 36 kgf.
On average, the frame connections in the doors withstood a tensile force of about 550 kgf, but only 231 kgf at break. You can compare the relative strength of connections in each category using the tables. After analyzing the columns of numbers, we found several features that you can implement in your workshop to make connections stronger.
FRAME CONNECTIONS
Half-tree connections
Result. In the fracture test, half-timber joints withstood twice the load of the next strongest joint. Conclusion. Large area gluing along the fibers gives this connection exceptional strength. Use it on mirror frames and heavy doors to ensure their reliability.
Result. In the tensile tests, for most of the half-timber joints, it was not the glue that broke, but the wood on the studs. Conclusion. This connection is capable of holding heavy inserts, such as stained glass, in doors.
Result. Coarse saw blade marks could be seen in joints with broken glue. Conclusion. For a strong bond, sand the contacting surfaces of the joint smoothly.
Result. Despite the fact that half-tree connections are primitive and easy to make, they are superior in strength to other, more labor-intensive connections, for example, counter-profile ones. Conclusion. Greater complexity does not guarantee greater strength.
Connections with semi-concealed tenon
Result. In each tensile test, the socket post was torn lengthwise through the wood before the tenon on the crossbar broke. Conclusion. The gluing along the fibers of the walls of the nest and the cheeks of the tenon is quite strong, but weaker than in half-tree joints.
Result. In tensile tests in all samples, the cracks in the posts coincided with the bottom of the socket. Conclusion. Long tenons reduce the likelihood of cracking and strengthen the connection, as in previous tests.
Result. In none of the images tested did the spikes break or even show signs of weakness. Conclusion. The repeatedly practice-tested rule of making studs with a thickness equal to a third of the thickness of the parts has once again proven the sufficient longitudinal strength of the studs.
Result. In several specimens tested for fracture, the tenons broke the wood between the socket and the end of the post (see photo), but not before the posts burst lengthwise. Conclusion. Use this connection for applications where increased reliability is required. The strength of the tenon's gluing is more than sufficient, despite the vulnerability of the thin wall of the socket.
Result. The connection weakens when the end of the tenon does not reach the bottom of the socket. Conclusion. The gap between the bottom of the socket and the tenon to collect excess glue weakens the connection. Try to keep it to a minimum and not apply too much glue.
Tongue and tongue joints
Result. As with semi-bursted tenon joints, the posts break along the bottom of the tongue during the tensile test. In all cases, short tenon-ridges 10 mm long were firmly held by the adjacent walls of the grooves.
Conclusion. Since the length of such tenons is limited by the depth of the tongues in the racks, pay attention special attention careful fitting and gluing of all elements of such a connection, including the ends and shoulders of the tenons.
Result. The ends of the tenons tore off the wood fibers at the bottom of the tongues. Conclusion. Glue does not fill gaps in joints well. A precisely adjusted tenon length increases strength and improves the appearance of the joint.
Counter-profile connections
Result. Despite the profiled edges of the posts and crossbars, these joints were found to be approximately equal in strength to tongue and groove joints in tensile and fracture tests. Conclusion. Profile joints do not weaken the connection.
Result. In all tensile tests, the posts split at the end of the crossbar tenon. Conclusion. The joint shown on the right fails where the fibers are twisted or angled. For strong frames, choose straight-grain wood.
Result. Even the gluing of end and longitudinal fibers in such joints exceeds the strength of the surrounding wood. Conclusion. The connection is quite suitable for frames with panels.
Conclusion
It cannot be considered a coincidence that the two strongest connections were with largest area gluing longitudinal fibers. For frames with heavy glass or mirrors, choose half-timber joints, especially in cases where the width of the frame is greater than its height. Semi-hidden tenon joints work the same way, with the tongues in the posts and crossbars being made into blanks before the joints themselves are made. Use them in doors that are frequently opened.
You should also not neglect counter-profile connections, as well as tongue and groove connections. In real conditions, four such connections in the corners of the door will give four times greater strength, and filling with panels will additionally strengthen the structure. Both of these connections are strong enough for normal use, but will not withstand too much rough handling. The strength of any joint can be increased by using straight-grained wood and careful fitting and gluing of elements with smooth surfaces.
Box connections
Straight box tenons
Result. The gluing of straight tenons turned out to be quite strong - in tensile tests, the fibers and edges of the tenons on both parts of the joint were split. Even when gluing the end fibers with the longitudinal ones, the corners of the individual tenons chipped off. Conclusion. In connection with straight box tenons of 12 mm thick parts, the gluing area is 24 cm2, and half of this area is accounted for by gluing longitudinal fibers. Use these joints in areas where the greatest tensile strength is required, such as in drawers for storing heavy items.
Result. To our surprise, the fracture strength of these joints was much lower and was only 4 percent of the tensile strength. Conclusion. Reinforce such joints with thin nails, driving them into the outer tenons on both edges.
Mushroom connection with lock
Result. In all samples, the tapered ridge remained glued to the mating groove. The strength of the connection is ensured by gluing the longitudinal fibers. Conclusion. These joints combine strength and beauty with neat joints at the outside corners.
Result. Narrow bevels at the outer and internal corners reduce bonding strength.
Conclusion. Select a cutter profile to minimize the width of these bevels.
Result. In both tests, the specimens failed almost equally when the ridge broke at the base.
Conclusion. Since the ridge formed by the cutter is expanded at the base, such joints are stronger than tongue-and-groove joints.
Tongue and groove connection
Result. Despite the fact that in each section the longitudinal fibers are in contact with the end fibers, the strength of the gluing of tongue-and-groove joints exceeds the strength of the wood itself. The joints fail when the outer wall of the groove breaks off completely from edge to edge. Conclusion. By using a tongue-and-groove connection to attach the back wall of the box to the side walls, you can increase strength by placing the grooves in the side walls at a greater distance from the ends.
Result. On the destroyed joints we found areas with burn marks, where the bonding strength was low. Conclusion. Wood with burns does not absorb glue well. When making these connections, reduce the rpm of the cutter or sand down any burn marks left by the saw blade.
Open dovetail connection
Result. In tensile tests, the end faces of the eyelets separated from the longitudinal fibers of the side wall, leaving almost no marks.
Conclusion. For greater strength, carefully apply glue to the edges of the studs and longitudinal grain lugs.
Result. Despite the careful work, there were almost no traces of glue on some of the spikes. Conclusion. Lubricate both parts with glue so that after squeezing out the excess, there is enough glue left in the joint.
Result. Even after the bond fails due to excessive load, the parts remain mechanically connected. Conclusion. Unlike other joints, weak gluing does not lead to complete destruction of the box if the tenons are located on the front and back walls, and the eyes are on the side.
Keyed connection with dovetail groove
Result. All specimens in both tests failed when the 3 mm wall between the groove and the end of the board broke off. Conclusion. This connection is best used for drawers in which the part with the tongue can be installed further from the end of the part with the groove.
Result. In both tests, these joints were found to be less strong than similar tongue-and-groove joints, which can simply be cut on a saw. Conclusion. Considering that one joint piece needs to be pushed into another, making it difficult to install the bottom, you may find it easier to make drawers with tongue and groove joints.
Seam connection reinforced with nails
Result. Despite the absence of parts with small elements, such as in miter joints with a lock or in keyed joints with a dovetail groove, here the thickness of the parts does not lead to an increase in the strength of the connection. During the tensile test, only one of the three samples showed a crack along the end of the rebated part. In the rest, destruction occurred along the adhesive seam connecting the longitudinal fibers with the end fibers. Conclusion. Even with mechanical reinforcement using three nails, the gluing of the end and longitudinal grains was much inferior to the strength of the wood, unlike most other joints.
Result. Nail heads partially or completely penetrated the rebated part in the tensile test, and only two nails did so in the fracture test specimens. Conclusion. Nails help hold parts in place during box assembly, but don't rely on them to make up for weak glue.
Tongue-and-groove connection with two shoulders
Result. Weak point Such connections turned out to be a thin strip between the wall of the groove and the end of the part. Conclusion. This connection is best used when the groove can be located further from the end of the side wall of the box.
Result. The ridges were 4 mm thick, but none of them broke during both tests. Conclusion. High-quality gluing ensures the strength of even thin spikes and ridges.
Result. In tensile tests, two samples developed cracks at maximum load, but the joints did not fail. Conclusion. At the first sign of cracking, apply a liberal amount of glue to the sides of the end grain groove and you may be able to save the part. 
Semi-concealed dovetail (top right)
Result. In tensile tests, the adhesive joints failed quickly, but the parts remained together due to the shape of the mechanical locking elements. Conclusion. You can disassemble the dried connection, remove old glue and re-glue the box.
Result. In tensile testing, the rounded interior of some studs broke off under load. Conclusion. Reduce the rotation speed of the cutter to avoid burns on both parts of the connection. Then apply glue to both parts, not just the sockets.
Conclusion
Choose straight tenon joints for drawers that are subject to rough handling, yanking, or if they are used to store heavy items. If appearance is important and you don't want the end surfaces to be visible at the corners, choose miter joints with a lock that have almost the same strength. Tongue-and-groove joints are simple to make and are strong enough to fasten the back wall of the box, located at a distance of at least 2-5 mm from the ends of the side walls. Open dovetail joints formed by a router lack fracture strength, but are considered among the most repairable joints, which is why they are so popular in heirloom furniture. Dovetail keys are not particularly durable or practical.
If the bottom will be inserted into the tongues of all four walls of the box, you must choose a different connection option for the front or back wall. Nail-reinforced rabbet does not look very elegant, but it is easy to make and suitable for attaching front and back walls, which undoubtedly makes it very convenient for making ordinary boxes that do not have high demands.
Instead of tongue-and-groove joints with two shoulders, it is better to choose a miter joint with a lock, unless you are forced to work only with a saw machine. Semi-concealed dovetail joints are not as strong as other joints, but they look impressive, are not visible on the drawer front, and they can be re-glued together, just like an open dovetail joint.