I'll introduce you to new material. You will not only listen carefully, but watch how I connect the details.
My explanation will be supplemented by the guys who worked with encyclopedias and technical reference books. They have prepared important information for you.
After the explanation, there will be a blitz tournament (poll) on the new topic.
Most joinery consists of several parts. In order to obtain a finished product from individual parts, they must be connected to each other. Joining wood parts is often done with nails, screws and glue. Today we will learn how to connect parts using nails and screws.
In Russia, the production of nails has been known since the 13th century, but only in the 19th century were the first machines for their production created. Now nails are made using automatic machines.
Hammered nails are held in place by pinching between the wood fibers.
A nail has a head, shaft and point.
Nails are standard parts. They differ depending on the destination.. (write in notebook)
(The teacher demonstrates different kinds nails)
Nails come in different sizes. Depending on the length of the rod (40, 50, 100 mm, etc.), nails in everyday life are often referred to as "magpies", "fifties", "hundreds", etc.
Before hammering a nail, mark the joints and make indentations with an awl.
When connecting parts with nails, usually a thin part is nailed to a thick one.
The thickness of the nail should not exceed 1/4 of the thickness of the part being nailed. The length of the nail should be 2-3 times the thickness of the part to be nailed. It must be remembered that the connection will be stronger if the nail enters the main part across the fibers and less strong if along the fibers.
To prevent the part from splitting, the nail should be hammered at a distance of at least 4 nail diameters from the edge of the part and at least 15 diameters from the end.
Nails are hammered by carpenters hammer .
The hammer should be held so that the hand is at a distance of 20 ... 30 mm from the end of the handle. First, the nail is held large and index fingers left hand and apply light blows to the nail head with a hammer.
(The teacher demonstrates how to perform this operation)
After the nail has firmly entered the wood, the left hand is removed and harder blows are applied.
You can avoid splitting wood when driving nails by first slightly blunting the nails by hitting their point. Such a nail displaces the fibers of the wood without tearing them, so the part does not split.
(The teacher demonstrates how to perform this operation)
If the nail went crooked or bent when hammering, it must be pulled out. For this purpose, apply ticks or a hammer with a special slot on the toe.
In order not to damage the surface of the product, a piece of plywood or a small plank is placed under the jaws of the pliers or the head of the hammer, they grab the nail by the cap or rod and pull it out of the wood by turning the tool.
(The teacher demonstrates how to perform this operation)
If the ends of the nails protrude, they are bent on a mandrel and hammered back into the wood. This increases the strength of the connection.
(The teacher demonstrates how to perform this operation)
A hammered nail is pulled out as follows: the bent end of the nail is bent with a chisel. Align it with pliers or pliers. The end of the nail is knocked out with a hammer, and then pulled out by the head with tongs.
(The teacher demonstrates how to perform this operation)
Work on connecting parts with nails is most often performed by a carpenter .
Will tell us about this profession
And now I will introduce you to the connection of parts with screws.
Screw connection is more durable than nails.
Screw - it is a fastener consisting of a head and a threaded rod. The term "screw" - German origin, translated means "screw".
Like nails, screws are standard parts. Depending on the purpose, the screws are made in different lengths and thicknesses,
(Teacher demonstrates different types of screws)
as well as with various form heads: semicircular, hidden and semi-secret.
Most often, screws with a countersunk head are used, since it does not protrude above the surface of the part.
1. Wood screws
- Head: recessed semicircular
2. Screw for sheet metal
- Head: cylindrical - oval - round
- Used for: fastening thin sheets of metal or plastic. These screws are self-tapping.
3. Threaded dowel (screw with thread on both ends)
- Head: wood carving (metric)
- Used for: hidden connections wooden panels, beams, etc.
4. Wood screw or hex screw
- Used for: fastening heavy beams and other building elements made of wood
5. Screw for hanging mirrors
- Head: recessed
- Used for: hanging mirrors and bathroom accessories. The head of the screw is closed with a chrome-plated or plastic cover.
6. Wood screw
- Used for: general woodworking
7. Wood screw
- Head: oval
- Used for: fixing metal products and accessories. The head of the screw protrudes from the surface of the wood.
8. Connecting screw
- Head: recessed
- Used for: fixing door hinges, plates and other decorative elements with slotted holes.
9. Wood screw
- Head: recessed
- Used for: a variety of woodworking. The head of the screw is recessed when it is tightened.
The screw heads have slots (straight or cross grooves) for a screwdriver. The term "spline" is derived from the German word meaning "gap", "groove".
When choosing a screw, it should be borne in mind that its length should be 2 to 3 times the thickness of the thinner part to be joined. However, the screw should not go through the main (thicker) part.
When connecting large parts, use large screws with a square or hex head for a wrench. They have an unusual name - capercaillie.
Wood screws have a sharp point, so they go into the material like a wedge and split it. The material is subjected to a special load when the screw shaft enters it.
Currently, along with screws are widely used self-tapping screws.
Unlike screws, self-tapping screws start from the head of the rod itself.
The places for installing screws are marked in the same way as for nails. In a thinner part, a through hole is drilled with a diameter slightly larger than the diameter of the screw.
In the main part into which the screw is screwed, a blind hole with a diameter of 0.8 of the screw diameter is drilled to a depth equal to the length of the screwed part of the screw. For thin screws, holes can be pierced with an awl.
For countersunk and semi countersunk screw heads countersink with a large diameter drill or a special tool - countersink - expand the inlet.
The terms "countersinking" and "countersinking" come from a German word meaning "to deepen" in translation. The diameter of the drill and countersink must be equal to the diameter of the screw head.
After preparing the parts, the screw is placed in the hole and screwed screwdriver clockwise.
Choosing the right screwdriver is also important.
If you take the wrong size screwdriver, you can damage the slot on the screw head with it, after which, even if you use force, it will be impossible to tighten it.
(The teacher demonstrates an example of connecting parts with screws)
At the enterprises of the woodworking industry, assembly work (including with the help of screws) is carried out by carpenters and assemblers of wood products.
Will tell you about this profession
So, you listened carefully to my explanation and carefully followed the technique of performing operations.
JOINING THE PARTS ON THE NAILS Many of the woodwork you will be making in the training workshops will contain multiple pieces. They are interconnected different ways. The process of connecting parts into a whole product is called assembly. Many wood products that you will make in the training workshops contain several parts. They are connected to each other in various ways. The process of connecting parts into a whole product is called assembly.
Depending on the location of the parts in the products, end and middle connections are distinguished. They can be made with nails, screws or glue. End Connections Middle Connections The industry produces nails of various thicknesses, lengths and with different heads. The main tools used to connect parts on nails are a carpenter's hammer, pliers and an awl. Carpentry Hammers Awl Pliers
When connecting parts with nails, a thin part is nailed to a thick one. In order for the connection of parts to be reliable, the length of the nail must be 23 times the thickness of the nailed part. The diameter of the nail must be less than the thickness of the part being nailed, otherwise a crack may appear in the part. The place where the nail is driven in must be at least half the thickness of the part from the edge or end of the part. It is advisable to pre-pierce it with an awl. The nail begins to be hammered with gentle hammer blows, and when it enters half of the rod, it is necessary to hit harder. Hammer blows on the nail are applied from above, directly on the hat, and not at an angle to the nail shaft. The strongest connection is obtained when the nail is driven across the fibers or at some angle to them. If the nail went askew or bent, don't worry! Such a nail must be removed with a hammer with a special slot on the toe or with pliers. Punching holes with an awl Punching nails Punching nails at right angles to the grain of the wood Bent nails can be straightened on a metal bar or hard board and used in further work. In order not to damage the product, a piece of wood or plywood is placed under the jaws of the pliers or the head of the hammer. Pulling out nails with pliers Pulling out nails with a hammer
ATTENTION! You can only work with a serviceable tool, it must be used strictly for its intended purpose. When working, the hammer must be kept at a distance of 2030 mm (2 3 fingers) from the free end of the handle. Do not leave a carpenter's hammer on the edge of a workbench. You can not stand behind the back of a person working with a hammer. The tip of the awl should be directed away from the worker.
CONNECTION OF PARTS ON SCREWS Over time, the nail connection weakens: the nail can swing and even fall out completely. The connection of parts on screws is much more durable. Over time, the nail connection weakens: the nail can swing and even fall out completely. The connection of parts on screws is much more durable.
A screw is a fastener that consists of a head and a threaded shank. The head of the screw has a slot for a screwdriver. The slot can be straight and cruciform. Screws differ in the type of heads, which are semicircular, countersunk and semi-secret, as well as in the length of the rod. Most often, countersunk head screws are used. Such a screw does not protrude above the surface of the part. A screw with a semi-circular head A screw with a countersunk head A screw with a semi-counter-sunk head The places for installing the screws are marked in the same way as for nails. It is difficult to screw a screw into a part, therefore, in the workpiece, before installing small screws, a hole is made with an awl to a depth equal to about 2/3 of the screw length. For a countersunk head, a large diameter drill widens the inlet. The screw is inserted into the hole and screwed with a screwdriver clockwise. A screwdriver is selected in such a size that the width of its working part is equal to the width of the slot. The shape of the working part of the screwdriver should be the same as that of the slot. For thick and long screws, holes are drilled with drills. Their diameter is 4/5 of the diameter of the screw shaft, the drilling depth is approximately equal to half of its length.
ATTENTION! Use only a screwdriver that fits exactly into the slot of the screw head. The screw must be screwed in at right angles to the parts. When assembling parts, do not use screws with a knocked down slot. Screws lubricated with machine oil or soap are easier to screw into the part. The burr on the head of the screwed screw must be removed with sandpaper.
Most often to get adhesive joints use wood glue. It comes in the form of grains or dark brown tiles. Prepare the glue special utensils glue pot and use hot. The glue should not be very thick and without lumps. The glue is applied with a thin layer evenly on the surface of the parts to be joined with a brush and compressed with a clamp fixture. Wooden clamp Metal clamp After exposure (its time is determined taking into account the glue used), the glued parts are released from the clamp, the remaining glue protruding from the seams is removed. Sometimes synthetic materials are also used for gluing wooden parts. universal adhesives such as PVA, "Supercement", BF, which are widely used in everyday life for gluing products from other materials. However, synthetic adhesives emit harmful fumes. Therefore, their use requires special conditions: good ventilation of the premises, the presence of warm water for washing hands after work.
Finishing the final treatment of an assembled product in order to improve its appearance and protect it from moisture, insect damage, etc. Finishing a product includes several operations: cleaning surfaces, coating with dyes, applying patterns by burning, etc. These operations can be performed before assembly or after assembly of parts. Depending on the intended use of the product, some operations may not be applicable. Cleaning irregularities after sawing, as well as rounding the sharp corners of the workpiece, is carried out with a rasp or a file with a large notch. When filing left hand the worker should lie on the toe of the tool, not covering it. Press the tool only when it moves forward. Cleaning of parts with a file Cleaning of parts after manufacturing is carried out with a sandpaper. It is based on cotton fabric or thick paper, on one side of which small grains of glass or hard minerals are glued.
For convenience, a piece of sandpaper is attached to wooden block. It is convenient to grind small parts as shown in the figure. Cleaned parts or products are often painted with cotton paint, watercolor or gouache. A special stain is also used. Sometimes wood products are varnished, it gives it a beautiful look. appearance and protects the surface from moisture. Regardless of the type of dye, it is applied with a brush or swab with a piece of cotton wrapped in gauze. Cover the surface first along the fibers, then across. Applying color with a brush Applying color with a swab
To connect wooden parts to the structure, a connection with nails is used. The industry produces various types of nails. Common to them is their structure (Fig. 107).
At the same time, nails differ in the shape of the head, the length and diameter of the rod, the purpose, the material from which they are made, etc. (Fig. 108). Nails with a flat head were widely used (Fig. 109). Depending on these parameters, nails are used to connect thick and thin parts into a structure, for glazing windows, fastening fabric, rubber, metal and other structural elements with wood structural elements, etc. Thin nails are used to work with plywood and fiberboard.
Rice. 107. Structure of a nail: a - head; b - rod; c - point
Rice. 108. Types of joiner's nails: a - with a flat head; b - with a conical head; c - with a spherical head; g - with a convex decorative head; d - spiral
Rice. 109. Types of carpenter's nails with a flat head
The main tools that are used to connect parts with nails are a carpenter's hammer, pliers, tools for pulling nails (Fig. 110). When connecting parts, remember that you always connect a thinner part with a thicker one. In accordance with the dimensions of the blanks, the length and diameter of the nails are selected. The length of a nail that does not pass through should be 2-4 times the thickness of the thinner part, and its diameter should be 10 times less than its thickness.
Rice. 110. The main tools for connecting parts with nails: a - hammers; b - ticks; c - a tool for pulling nails
A nail is driven at a distance of at least 10 mm from the edge of the part, otherwise it may crack. If the nail needs to be hammered closer than 10 mm from the edge, a hole is drilled in the part, the diameter of which is 0.5 mm smaller than the diameter of the nail. When hammering a nail, the hammer is held by the handle at a distance of 20 ... 30 mm from its end (Fig. 111) and strikes at the center of the nail head. At the same time, the nail is held by the rod near the head (Fig. 112). The direction of impact must coincide with the axis of the nail, otherwise it will bend (Fig. 113).
Rice. 111. Hammer grip
Rice. 112. Holding a nail at the beginning of hammering: a - with fingers; b - pliers
The nail begins to be hammered with gentle blows of the hammer, and when it enters the workpiece by about a third of the length of the rod, the impact force is increased. To deepen the nail head into the wood, special cylindrical devices are also used (Fig. 114). To connect plywood parts, the places for driving nails are pierced with an awl (Fig. 115). If parts are connected with a through passage of a nail, its length should be one third more than the thickness of the connected parts. To do this, use a nail with a flat or conical head. The part of the nail that has come through is bent across the fibers (Fig. 116).
Rice. 114. Deepening the head of a nail with a cylindrical device
Rice. 115. Puncture of clogging points
If the direction of the nail has shifted or is bent, it should be removed. Such a technological operation is performed with pliers, a hammer or a special tool with a slot. In order not to damage the product when removing the nail, a piece of wood or plywood is placed under these tools (Fig. 117).
When making connections with nails, the following safety rules must be observed:
Rice. 116. Sequence of bending a nail
Rice. 117. Methods for pulling a nail: a - with pincers; b - with a hammer; in - a tool for pulling
Rice. 118. Schemes for fastening the hammer head with a wedge: a - correct; b - wrong
Rice. 119. Nozzle of the hammer striker: a - correct; b - wrong
nail, pincers.
1. The end of the hammer handle should stick out of the hand at
2. The nail is hammered into the workpiece at a distance from the edge not less than
3. When pulling a nail, a piece of wood is placed under the pliers to
4. The length of the nail must be greater than the thickness of the part to be nailed, in
5. The diameter of the nail must be less than the thickness of the part in
Nails and screws are the simplest and most affordable means for connecting wooden parts and fastening metal parts to wooden bases.
Our industry produces nails of a wide variety of varieties - round and square section, with a flat and conical head, with a length of 15 to 250 mm and a diameter of 1 to 8 mm, respectively (see table 1 at the end of the book), Depending on the type of work performed, the thickness of the material and the required strength, nails are used various sizes. The strength of the connection on the nails also depends on the number of driven nails, their direction in the layers of wood, the quality of the wood itself, etc. A long and thick nail holds on stronger than a short and thin one; a nail driven into the end of a tree is held much weaker than a nail driven across the grain.
It must be borne in mind that several closely spaced nails hammered into one layer of wood can split the workpiece (Fig. 52). The same thing can happen when driving a nail too close to the end, especially if the nail is thick and the board or rail is thin. The connection will be stronger if the nails are not driven strictly perpendicular to the surface, but with a slight slope.
Always nail a thin part to a thicker one, and not vice versa. The length of the nails should be 2-4 times the thickness of the thin piece. When nailing boards, you need to take into account the direction of their bending during warping.
So that the nail head does not spoil the appearance of the product, when attaching narrow decorative bars (glazing beads) to the doors of cabinets or paneled doors, the nail is not driven in completely, the head is bitten off, and then driven flush with the surface or even with a recess. The nail head can also be hidden by first flattening it with hammer blows (Fig. 52, D), and hammering it so that the resulting planes of the head coincide with the direction of the wood fibers. The hammered nail is deepened with hammer blows through the head of another nail laid sideways (Fig. 52. D), when finishing, the resulting recess in the board is puttied.
Sometimes when nailing a product, the nail passes through. The protruding end is folded into a hook and hammered flush (Fig. 52, E).
When driving a nail into the plaster, it often cracks. The nail will go better if it is first lowered into hot water or melted paraffin.
To avoid hitting your fingers with a hammer when hammering small wire nails, you can use simple fixture(Fig. 52, G). It is a spiral of thin steel wire, bent as shown in the figure. The carnation is placed between the coils, which hold it until it goes deep into the tree. The coils of the helix must be large enough for the head of the nail to pass freely through them.
Nails are usually pulled out with pliers or hammer horns. If the nail is completely hammered into the board, before pulling out, it is necessary to make a gap between its head and the surface of the board, otherwise it will not be possible to grab the head. To do this, either cut the wood or, if the nail sticks out on the other side, it is knocked out a little. In order not to spoil the part with pincer sponges or a hammer, a piece of wood or an ax blade is placed under them.
More durable than on nails, connections on screws. Screws are issued with semicircular and flat (secret) heads. The head has a slot (slot) for screwing with a screwdriver (Fig. 53). Screws are made in various lengths - from 6 to 120 mm (see table 1 at the end of the book).
At home, screws are used quite often: for attaching plank sheathing, plywood, hardware to wood, screwing switches, sockets, etc.
When using screws, you must adhere to the following rules. First, mark with a pencil or awl the places where you want to screw the screws. After that, use a gimlet or drill to make a hole with a diameter slightly smaller than the cylindrical part. For the screw part of the screw and for small screws, the hole can be pricked with an awl. It is much more difficult to screw screws into a whole tree without pricking holes, the strength of the connection does not increase from this, and besides, it can end in splitting the part. Screws are screwed with a screwdriver until the head stops against the surface. The slot of the head is usually installed on a layer of wood.
For screws with a countersunk head, the hole near the surface is countersunk. You can do this with a bench drill, and if you don’t have one, it’s easy to make a convenient countersink yourself. To do this, the screw head from the bottom must be cut with a hacksaw, as shown in Figure 53, B.
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The materials were sent by Glebov A.A. teacher of technology and labor training, MOU "Veselolopan secondary school"
Target: teach students to choose the right nails and screws to connect the parts of the product; practice connection techniques.
Equipment: hammer, screwdriver, nails, screws, wood blanks.
During the classes
I. Repetition of the material covered.
1. Conversation on the following questions:
"What types of drills do you know?
How to determine drill diameter?
2.Practical task.
"Drill a hole in the workpiece using a brace (drill).
3. Message of the topic and purpose of the lesson.
II. Presentation of the program material.
1. Illustrative story.
Teacher. Depending on the purpose, the nails differ in diameter, length, and shape of the cap.
The teacher demonstrates different types of nails.
When connecting parts with nails, you must adhere to the basic rules:
"A thin piece is nailed to a thick one;
"the thickness of the nail should not exceed 1/4 of the thickness of the part;
"the length should correspond to 2-3 thicknesses of the part;
"distance from the edge 4 diameters;
"the distance from the end is 15 diameters.
The teacher demonstrates how to hammer in a nail and pull it out if the nail is bent or crooked into the workpiece. (See Appendices, fig. 32.)
To improve the strength of the connection, the protruding nails are bent on the mandrel.
The teacher demonstrates how to perform this operation. (See Appendices, fig. 33.)
To pull out the nail, the operations are performed in the reverse order.
2.Instructing on the rules for the safe use of a hammer.
Teacher. When working with a hammer, you must follow the safety rules:
"work only with a working hammer;
"do not stand behind a comrade working with a hammer;
"hit the nail head strictly vertically;
"Do not leave a hammer on the edge of a workbench.
3.Practical work.
Completing tasks:
On unsuitable material, connect the parts with nails.
"Practice in bending nails.
"Pull out the hammered nails.
4. Explanation and development of the connection of parts with screws.
Teacher. Now let's look at the connection of parts with screws.
The screw consists of a head (semicircular, countersunk and semi- countersunk), a shaft of various lengths and thicknesses with a screw thread. (See Appendices, fig. 34.)
The teacher draws the attention of students to the types of slots of the screw head.
Teacher. When choosing the length of the screw, it must be taken into account that its length should be 2-3 times the part to be connected (top).
A hole is drilled in the upper part slightly larger than the diameter of the screw, and in the lower part - 4/5 0 of the screw.
For countersunk and semi- countersunk screw heads, the hole is countersinked. (See Appendices, fig. 35.)
Screw the screw with a screwdriver clockwise. (See Appendices, fig. 36.)
The teacher demonstrates an example of connecting parts with screws.
To What do you think, which connection of parts will be more durable and reliable - nails or screws?
At the enterprises, assemblers perform the operation of screwing screws with the help of electric screwdrivers, pneumatic screwdrivers.
5. Instructing on safety rules when connecting parts with screws.
Teacher. The main safety rules are:
"do not use screws with a knocked-out slot;
"use only a working screwdriver;
"screw in the screw only at a right angle;
"when screwing in, do not touch the screw with your hands;
After screwing in, deburr the screw.
6.Practical work.
On unsuitable material, practice screwing in screws, having previously selected screws and a screwdriver.
III. Summary of the lesson.
The teacher evaluates the quality practical work, indicates typical mistakes made by students.
