For any repair, self-tapping screws and screws are actively used. On sale you can find a great many different modifications, some of them are designed for wooden structures, the other helps to connect metal parts, furniture elements, glass products. Knowing what kind of self-tapping screws are, what sizes they can be, why many screws are made of different materials, you can try to correctly complete the task. To clarify such a question, you need to put everything on the shelves and draw up detailed instructions.
Initially, it is important to understand that each screw element has a narrow focus and its own marking.. Experts draw attention to the following parallel: in working with metal, it is necessary to use a metal oxidized self-tapping screw, a roofing screw with a roof, and wood screws with a tree. This distinction is the basis of the basic qualifications of the described tool. The fixing screws vary in appearance, size, cap shape and thread, each with its own price. Knowing how different types of self-tapping screws look, what designs have wood screws or wood screws, how to read the proposed markings, you can easily navigate the existing assortment. Therefore, it makes sense to talk about this in more detail.
Screws for working with metal
Despite the fact that the subject of the article is a description of the fixing screws intended for joining wooden elements, it is necessary to initially tell a little about their brothers - metal self-tapping screws. It is quite difficult to mix them up with other screws, they are made of high-quality metal, the turns on the pole are located very close to each other. The small inter-crest space provides better adhesion of the screw to a hard metal surface. As a rule, screws for metal have a coal-black or oxidized color, the price of 1 kg is higher than the price of 1 kg of screws intended for fixing wooden bases.
The diameter of the shaft of a conventional screw for connecting parts can vary (from 3.5 mm to 5 mm). The longer the barrel, the thicker the product. The following table helps to see the dimensions of metal screws.
Length (mm) | Thread pitch (mm) |
10,0-50,0 | 5,0 |
60,0-100,0 | 10,0 |
110,0-120,0 | 15 |
125,0-220,0 | 20 |
The parameters given in the table are basic, but they are only indicative. Many manufacturers do not take into account GOST and independently adjust the indicated parameters. It is their importance to consider when buying screws to solve specific problems. To connect parts made of thin tin, there is no need to make a hole with a drill first. If the thickness of the workpieces exceeds the specified thickness, it is necessary to drill a hole whose diameter is larger than the diameter of the connecting screw element.
Press plate screws made of galvanized steel are selected for fastening sheet metal, up to 0.9 mm thick. There are white wood screws. This is one and the same fastener, it just has a wide functional purpose. A washer located on top of the screw provides a tight hold on the two elements. On sale you can find both the shortest self-tapping screws (their length is only 13 mm) and the longest (64 mm).
The screws, the design of which consists of a barrel, an upper washer and a lower drill, are intended for fastening metal up to 2 mm thick. The drill allows you to make the necessary hole, into which the bolt itself then fits well. Using such screws is quite convenient. They help save time and securely fasten.
Wood screws
Almost all wood screws have a rare step in the intercostal space. The distance between two ribs is greater than that of metal screws. This feature is explained simply: wood is a less dense material than iron. On sale you can find wood screws in different colors (black, galvanized, golden). Color affects specifications. The yellow (anodized) screws are protected by a special compound, it helps protect the described elements from rust. Black screws rust very quickly. In addition, the color allows you to provide a wide selection for the selection of design performance. So, for example, in order to nail a furniture loop made of yellow wood, it is better to choose a screw to match her.
When buying, it is important to pay attention to the length of the screws. It is commensurate with the density of the compounds. So, for example, if you want to fasten two wooden parts together with a width of 50 mm, you need to choose screws for wood 75 mm long for fastening. Is the principle of length selection now clear?
The next moment. All wood screws have different diameters. Those of them that in the radius from 3.5 mm to 4.2 mm according to GOST do not require pre-drilling for their screwing. Other screws are screwed differently. Wood is not metal. If there, the screw hole is made a little wider than the diameter of the screw, when working with wood, the situation changes in the opposite direction.
So, for example, in order to screw in a black or yellow (anodized) screw with a diameter of 4.5 mm, it is necessary to drill a hole with a diameter of 3.5 mm. A 5 mm hole is drilled under a 5 mm self-tapping screw. Only in this case, when fastening, the wooden workpiece will not crack. To accomplish this task, a conventional metal drill is used. Violation of the indicated proportions can lead to another problem - the lack of adhesion density and the fragility of the assembled structure as a whole.
Types of thread screws
It is the screw thread that determines its scope. There are three varieties of thread. All of them are presented in the following table.
Types and types of threads | External execution | Application area | Price rub / pack |
Coarse thread with a wide step | They are used for joining elements made of wood, drywall, fiberboard, chipboard, MDF sheets. | from 62 rub. (200 pcs.) | |
Fine thread with low pitch | They are used for joining parts made of especially hardwood. | from 141 rub. (100 pieces) | |
Two-way thread (alternating high and low turns) | They are used to join materials with different densities (drywall and wood frame, for example). | from 100 rub. (200 pcs) |
Classification by other components
What else needs to be paid attention to? Specialists distinguish screws by:
- The material of manufacture (screws made of carbon steel, stainless steel, brass).
- According to the outer coating (phosphated and oxidized (they are black in color and quickly rust), galvanized, galvanized yellow (anodized), uncoated).
- Standard threading (rare and frequent).
- At the end of the trunk (sharp self-tapping screws and drill bits - self-tapping view).
Of particular note is the plurality of types and types of heads for self-tapping screws used for woodworking. The following table will help to identify all existing options, as well as their features.
Types of heads | Their purpose |
Countersunk (ISO 1482, for example) | Such a self-tapping screw has a round head in the shape of a funnel, after completing the fastening, it is completely recessed in the material, there are no protrusions on its surface at the attachment point. |
Hemispherical | Provides a wide pressing area, it allows you to make a firmly bonded connection. |
Hemispherical with a press washer | It is used according to GOST for fastening sheet materials. A characteristic feature of the form is a wide area of fit and a reduced length of the column. |
Reduced countersunk | A distinctive feature is a smooth transition from the head to the pole, when fastening, the self-tapping screw is fixed in both fastened elements, during installation it requires more effort. |
Spherical head with large press washer | The largest bearing surface with a small head height. It is used for joining soft sheet materials. |
Hex head | A screw designed to work with a screwdriver and nozzles for it. The most common type of screw, easily screwed in by hand. |
Funnel-like head, countersunk, with hex key | It is used where it is necessary to hide and mask the place of attachment with a beautifully decorative button. |
In conclusion
Those who study the proposed characteristics more closely will be able to easily find the answer to the question of how to choose self-tapping screws if you need to work with wood or metal. Such an element is able to provide reliable fastening if it is used strictly for its intended purpose. Summing up certain results, it can be noted: to distinguish a wood screw from a screw for metal is quite simple.
- Firstly, it has a much larger pitch than a metal screw. This is because the density of the tree is less, it is softer, the structure of the fibers is porous.
- Secondly, the screws intended for fastening wooden products have narrow and sharp tips, which is why the hole that is made with them is obtained with smooth walls.
And another important point, the cost of hardware for wood is much lower than that which have elements designed to work with metal products.