Perhaps, it is not possible to find more reliable assistants when doing repair or finishing work, than screws. These staunch "steel soldiers" are able to withstand literally any fastening for soft materials. How to independently choose the screws from the great variety of fasteners?
Content
For an hour the blond girl in a pink hat was standing by the window in the building supermarket and was examining the fixing elements. She brought her here a request from strict Petrovich, who was doing repairs in the blond's apartment. "Go, buy the screws," Petrovich said, and wrote something on a piece of paper. "Here are these," - the master handed the blonde a note. "460s 4-40", - was written on a piece of paper in a box.
Secret entry
"What is 460?" - Blond thought, considering the screws, bolts, screws and screws, which were laid out in the display case. "Probably something secret, since the letter" c "is available." To the blonde was not boring and sad, let's help her to figure out what kind of screws there are.
Screws (screws) for fastening wooden and plastic parts, namely for such purposes screws are used, are manufactured by industry, according to existing standards. According to GOST the screws are made of stainless steel, brass and cover them to improve the anti-corrosion properties of zinc, brass or chrome.
Kinds of heads (screws) of a screw
Looking more closely, the Blonde suddenly exclaimed in surprise: "So they have different hats". Yes this is true! The head of the screw in its form differs into a spherical, flat and hexagonal, less often square. The dimensions and shape of the screw cap are standardized. Therefore, it is necessary to distinguish the screws:
• Countersunk head
• with semi-countersunk head
• having a semicircular head
• with hexagon head
• having a square head.
Screws having a countersunk head are used for those jobs where the head arrangement is provided flush or below the working surface or must be recessed. The screw head in this case enters the existing conical hole - a chamfer. To strengthen the clamping moment for screws with a countersunk or semi-hollow head metal washers are used. Use also plastic sockets with a decorative cap, which, after installing the screw, closes the head.
With a semi-hollow head screws are a cross between a semicircular and countersunk head. This type of screws is used to use the fastening of metal elements to wooden elements.
Screws with a semicircular head are used for fastening with sheet materials, in the case when the thickness of the material is too small for the use of a countersunk head.
Self-tapping screws, the owner of a hexagon head (wood plow) is applicable for fixing structural elements without preliminary drilling. Due to the high class of strength of production and the galvanized surface of the screw, any working surface (concrete, brick or wooden) can be drilled at the same time.
Due to the presence of a figured slot on the screw head, a screwdriver type must be chosen for operation. Slots can be straight and cross Philips or Pozidrive.
Types of screw threads
"Oh, look, but there are thin screws with carving, but in half with carving" - the pink hat of the blonde swung from surprise.
In addition to the head of the screw there is a whole body. The body of the screw is a third of the total length. And some screws have a continuous thread along the entire length. The end of the screw is a sharp tip, which allows you to drill into the surface with a screwdriver or electric drill. The thread of the screw allows you to screw in without damage to the surface.
Therefore, the possibility of screwing into the surface of the screw is carried out due to the thread on the whole body. And it should be noted that the characteristic screw thread visually differs from that of other fasteners. Screw thread is higher and has a significant cutting step. As a rule, the threaded portion of the body has the shape of a cone and tapers to the end of the screw. In this case, the thread is cut along the entire length of the whole body, and in a separate section.
Screw dimensions
When purchasing screws, you must always specify their size. So the length of wood screws is measured from the tip of the cone-shaped part to the head.
It is also necessary to determine the diameter, shape of the head and the type of slot. The screws can be in the range of 6 mm. up to 63 mm. The diameter is measured by the cross section of the whole body. Dimensions of the diameter start from 3.5 to 6.5 mm. The smallest screw, called the "bug", has a working length of only 8 mm. and a diameter of 4 mm.
A screw of a giant size, called "track", has a working length of 170 mm. and a diameter of 24 mm. The relationship between the length and diameter of the screw is denoted by a number and in practice of fundamental importance do not. The only thing to remember is that the higher the number, the thicker the diameter of the screw. The most popular and demanded diameters are: 2, 3, 4, 6 mm.
It is recommended to purchase screws one by one. In any economy, screws of different sizes will be useful.
The most common sizes of screws are: 25 (length) x 3.5 (diameter) mm, 38 x 4 mm, 50 x 4 mm, 63 x 5 mm. For work you may need screws with a straight and a cross-slot. Screws having a cross-shaped slot are twisted with a special cross-head screwdriver. The end of the Phillips screwdriver is tight enough and it fits securely into the recess of the slot. The most common cross type of the screw is Pozidriv with a characteristic slit of the octagonal star.
Do you want to know tips for choosing screws from professionals? Then study the proposed video, which will help to make a choice.
Return of the blonde
After watching the video and finally selecting the necessary screws, the blonde slowly returned home. The door was opened to her angry Petrovich: "God, well, where you are all day! Has she bought it? "The happy blonde handed Petrovich a bag of screws.
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