- Rules for choosing a connection depending on the type of load
- How to make a spike connection
- How to splice boards with glue
- How to weld structural members
- Connections with ad hoc links
It will be useful for novice home craftsmen to learn about the methods of joining wooden parts. We devote a short educational program to this topic, which will describe the main types of joinery joints and rallies with the use of glue, nails, screws or dowels, or without them at all..
Rules for choosing a connection depending on the type of load
The most simple end connections, they are used if necessary to build up a part. These joints are best suited to withstand compressive loads, but good resistance to twisting, stretching and bending can be achieved by cutting down specially shaped locks. The standard end connection is trimmed to half the thickness of both parts. The cut can be straight or oblique, if necessary, to prevent bending, stretching or twisting, a thorn or an obtuse angle is cut at the end of each cut, or the cut is made stepwise, forming a kind of “lock”.
1 – a straight overlay in a half-tree; 2 – oblique pad; 3 – straight strip with a stepped joint; 4 – half-wood overlay with an oblique joint; 5 – oblique patch lock; 6 – half-wood connection with an oblique thorn
Corner and side joints are used to connect straight parts into a truss or frame. Usually this part of the structure is a supporting one, so the main loads fall on displacement and compression. If the structure is subjected to the stipulated static load, a rectangular spike is cut on one of the parts, and a groove or eyelet of appropriate dimensions is cut on the other. If action to break the structure is possible, the tongue and groove are cut in the form of a trapezoid..
Corner joints: 1 – with an open through thorn; 2 – with a deaf closed thorn; 3 – with a through oblique thorn
Overhead cross and T-shaped connections are used, as a rule, for additional connections between critical structural parts. The main load in them is on compression, displacement and rupture. The first two types of loads are eliminated by cutting half a tree or less, followed by aligning the parts. The shoulders of the notches take the main load on themselves, it remains only to secure the connection with screws or overhead brackets. In some cases, a dowel is used to strengthen the connection or a thorn with a wedge is cut.
1 – half-wood cross connection; 2 – cross connection with landing in one socket; 3 – T-shaped connection with a hidden oblique spike; 4 – T-shaped connection with a straight stepped plate
A separate type of connections is box-type. They are intended for joining boards at right angles. Usually, for a box connection, teeth are cut on each board, the width of which is equal to the distance between them. On different boards, the teeth are cut with an offset, so when joining, the corner from the boards looks like one whole. The teeth can also be wedge-shaped, which prevents the angle from breaking in one direction, or they are additionally fastened with glue or nails.
Box corner joints: 1 – with straight through thorns; 2 – with oblique through thorns
How to make a spike connection
To make a spike connection, you need to circle both parts with a marking line on all faces at a distance from the end equal to the width of the connection. On two opposite sides and the end, the body of the thorn is marked with lines, the markings on both parts are completely identical.
The thorn is cut from the sides with a hacksaw for a cross-cut and the wood is chipped with a chisel. The width of the stud is made 2-3 mm larger for subsequent precise processing with a knife or chisel. The groove is cut with a hacksaw for longitudinal cutting and chipped with a chisel, also leaving a small allowance for processing. This is followed by fitting, in the process of which the parts are combined and achieve the most snug fit..
With a T-shaped spike connection, a central spike or groove is cut on one of the parts, and an eyelet is hollowed out or two side cuts are made on the other, depending on the type of the first part. To make the eyelet, a chisel is used, turning the inclined part of the blade into the hole. If the eyelet is not solid, I make the spike 8-10 mm more depth and cut off its end in the form of a deployed wedge. So when hammering, the spike will open itself, and the part will be firmly planted.
To connect wide parts, you can use a box connection by cutting several pins and grooves. The easiest way to secure a tenon joint is to drill through it across the tenons and hammer a wooden dowel into the hole (window gusset).
How to splice boards with glue
A very popular method of joining boards and beams is longitudinal and transverse gluing. When joining the boards with the wide side, the end can be even, although in most cases a tongue-and-groove profile is used. A tight fit of the parts is very important so that the adhesive layer is as thin as possible, this is the only way to achieve maximum strength. Sometimes a small amount of cotton fiber is applied to the butt greased with glue, this improves the quality of the bond.
The boards can also be connected in profile, but this will require wedge-shaped toothed cutting of both ends with an offset to the floor of the tooth for different parts. At home, such an operation can be performed using a handheld router..
For gluing parts, casein glue or high concentration PVA is used; sifted wood flour is added to the adhesive to give strength. The surfaces are covered with glue and kept in air for 3-5 minutes, after which they are placed under oppression or squeezed with clamps. Such a connection is stronger than the wood itself and never breaks at the joint..
How to weld structural members
For supporting structures, two types of connections are used – extension and articulation. The easiest way to fuse two pieces together is to make a half-thickness cut with a hacksaw at the same distance from the ends, and then chop off the excess wood with an ax. After matching the two parts, the connection is usually fastened with two overhead strips nailed to the side of the cut. Bonding is also possible, but only with a tight fit of the parts.
The ends cut into half a tree can be brought together at almost any angle, this is the main method of connecting roof trusses. To fasten the parts together, an additional tightening bond is required: the timber is applied to the connected parts from the side at a distance of 30-50 cm from the corner and cut into half the thickness at the points of contact, and then the structure is fastened with nails.
Often vertical and inclined structures need support, for example, when connecting a rafter system to floor beams. In this case, a notch is made for the landing slots on the horizontal beam, into which the racks will be inserted. It is very important to observe the angle of inclination and make the undercut by no more than a third of the thickness of the bar.
Connections with ad hoc links
Almost all joinery joints are made with additional reinforcing ties. In the simplest example, the role of such is played by nails or screws..
When building up parts, the unit can be strengthened with a through bolted connection, clamps, brackets and wood grouses, or it is simply wrapped with cold-rolled wire. It is enough to fasten the spliced vertical supports with two overhead strips – wooden or metal.
Corner joints are most often fastened with staples, overhead plates or corners. In cases where it is necessary to maintain a small mobility of the connection, one through bolt is used, which either stitches across the place of the overlay of the parts, or pulls them in the longitudinal direction with a minimum offset from the overlay.
The attachment point of the special connection must be at least 10 diameters of the fastening element from the edge and must not have any defects. It is important to remember that often the bonds do not provide the overall strength of the connection, but only compensate for the unaccounted load.