Diameter of hole for screw in wood
It is difficult to do without self-tapping screws in almost any area of construction and repair. For example, it is difficult to hang the same shelves, pictures, cabinets without using self-tapping screws. The screws themselves are divided by type (for certain materials).
What is the diameter of the drill bit for the self-tapping screw?
What materials are commonly used at home? Items made of wood, metal, plywood, drywall - their installation is not complete without the use of self-tapping screws. Of course, without practice, you can bend the screws and break them, all due to lack of knowledge on how to work with these fasteners. Therefore, it is better to learn in advance how to screw in self-tapping screws.
Fastening elements are divided into many types. Most often there is a division into “for metal” and “for wood”. They differ from each other even in appearance. The difference lies in the thread ball, that is, the distance between the threads. The thread of self-tapping screws for wood has a larger distance between the turns of the thread (for metal there is a smaller distance).
If you confuse the screws and screw the screw into wood, for example, into a sheet of metal, the fastening will either bend or even break. A self-tapping screw for metal in wood will not hold at all, since the wood will not penetrate between the turns and actually does not hold.
As for self-tapping screws for metal, you can find 2 varieties - with a drill at the tip and without.
Drill diameter for wood screws
It is quite easy to identify a self-tapping screw for wood - it has a large distance between the turns (than a self-tapping screw for metal). Why is that? The reason is quite simple - wood is a less dense material than iron.
Such screws can be of different colors - black, white, gold. The color does not affect functionality, that is, this is not some kind of special marking, but simply different colors for selecting fasteners to match the color. Of course, if you have white furniture, then it is better to use a white screw.
It is impossible to determine by the colors what this self-tapping screw is for wood or metal, only by the distance of the thread.
Self-tapping screws can be of different lengths and you need to choose according to your tasks; there are the smallest ones - a little more than a centimeter long and there are long ones, more than 20 centimeters long.
Black screws are usually 3.5 and 4.2 millimeters in diameter. And yellow ones - from 2.5 to 5.5 millimeters.
Source: https://crast.ru/instrumenty/diametr-otverstija-pod-shurup-v-dereve
Self-tapping screws - variety of types and main sizes
Self-tapping screws are a type of fastener made in the form of a rod with a head and a special external thread that forms an internal thread in the hole of the object being connected. Self-tapping screws have a cylindrical surface with a triangular thread.
Self-tapping screws are a fastening material widely used in construction. They have a very wide variety of materials, sizes, shapes, and methods of application. To tighten it, you need appropriate screwdrivers or bits for screwdrivers. It will take a lot of time to talk about all the variety of self-tapping screws. Therefore, below we will talk about the most common types of this product.
Wood screws
The main difference between wood screws is the rare thread pitch. Unlike metal screws, wood screws have a noticeably larger distance between threads. This is explained by the fact that the density and hardness of wood is much less than that of metal.
There are black, white and golden self-tapping screws in color, which can be matched to the color of the material used. The most popular ones for use are black.
Screw sizes
The length of self-tapping screws ranges from 11 mm to 200 mm.
You can often hear how builders call the smallest screws “seeds” - because of their small size, similar to a sunflower seed.
Diameter of wood screws
According to the diameter of the rod, black self-tapping screws come in 3.5 mm and 4.2 mm, while yellow and white self-tapping screws have diameters from 2.5 to 6 mm.
Drilling holes for screws
There are often cases when, before fastening to a self-tapping screw, it is necessary to drill the materials being fastened (pass the fastening point with a drill). This must be done for dense and thin materials. For example, if you try to screw a self-tapping screw into dense oak wood without pre-drilling, the self-tapping screw will simply break off, bend, or significantly under-tighten to the end, and there will be no tightness of the connection (a gap will appear between the connected elements).
When fastening thin parts, pre-drilling is necessary in order to avoid cracks and splits in the thin material being attached.
You can select the diameter of the required drill for drilling for a particular self-tapping screw using this table:
Self-tapping screw diameter Drill diameter| 4.0 mm | 2.5-3.0 mm |
| 4.5 mm | 3.0-3.5 mm |
| 5.0 mm | 3.5-4.0 mm |
| 6.0 mm | 4.5 mm |
If the diameters of the drill and the screw are equal, the adhesion density will be very low or there will be none at all.
Tighten the black screws using a screwdriver with a PH2 connector or a similar bit. For golden screws - PZ bit No. 1, No. 2 or No. 3, depending on the diameter of the screw.
Self-tapping screws for metal
Self-tapping screws for metal, unlike screws for wood, are characterized by a frequent thread pitch with small spaces between turns.
The length is similar to wood screws from 11 to 200 mm.
Diameter 3.5 mm.
They have a PH 2 connector.
Black self-tapping screws for metal come with a drill and a sharp tip.
For self-tapping screws with a sharp tip, it is necessary to pre-drill the metal, except for cases of fastening thin metals (up to 2 mm). When the metal thickness is more than 2 mm, it is necessary to drill with a 2.8-3 mm drill.
Self-tapping screws with press washer
They are used for fastening a wide variety of materials: metal, wood, soffits, siding and many others.
The large head, called a press washer, allows you to press the material being fastened tightly without using a washer.
- Have a rod diameter of 4.2 mm
- Length from 13 mm to 64 mm.
- PH 2 connector
Roofing screws
Self-tapping screws with a hexagonal head have a wide range of applications, but most of all they are used for fastening roofing coverings such as metal tiles and corrugated sheets, as well as components for them, for which they received the general name “roofing”.
- The length of self-tapping screws with a hexagonal head varies from 19 to 100 mm.
- Rod diameter 4.8 and 6.3 mm.
They are equipped with a washer with a rubber gasket, which is responsible for the tightness of the connection, which is important for installing a roof (to prevent leaks).
In terms of color diversity, caps can be of very different colors: red, brown, green, white and others. The color of the cap is matched to the color of the material being fixed and is marked according to the Ral and RR color standards.
There are also self-tapping screws without painting - just with a galvanized head and washer.
To fasten (tighten) these screws, bits with an internal hexagon are used.
Bit size:
- for self-tapping screws with a core diameter of 4.8 mm - 8 mm bit
- with a rod diameter of 6.3 mm - 10 mm bit
Confirmat - furniture screw
.
Confirmats are used when assembling furniture.
The most used ones are 50 mm long with a hex head.
This type of fastener requires mandatory pre-drilling. There is a special confirmation drill for this.
To tighten the confirmations, use hexagons or bits for HEX 4 brand screwdrivers.
Construction wood grouse
A capercaillie is a thick-rod self-tapping screw with a hex head.
Capercaillie are widely used in fastening various units of heavy structures, where special strength and reliability of the connection is required.
When constructing pitched roofs, wood grouse are used for wooden rafter systems and interfloor ceilings.
- The thickness of the wood grouse's rod is from 6 to 10 mm.
- The size of the hexagonal head of wood grouse varies from 10 to 19 mm.
They are tightened manually with wrenches of the appropriate size, or with attachments using ratchets or power tools. Pre-drilling may be necessary.
For fastening to bases made of concrete, brick, foam block, etc., they are used together with a plastic dowel.
Source: https://krovli.club/strojmaterialy/samorezy-vidy-i-razmery
How to choose the right drill bit for metal screws
Do you need to securely fasten any element to a metal surface? Then you definitely need to use metal screws. Such fasteners are quite inexpensive, but at the same time they are reliable fasteners. Using them, you can do all the necessary work related to repairs several times faster.
These products externally resemble ordinary screws, although the difference is still significant, namely in the tip. For self-tapping screws, it is made in the form of a small drill (mini drill).
Therefore, the principle of screwing is that they first, as it were, cut through the surface, and then are screwed in using a screw thread. The metal cap allows you to firmly fix the work surface.
There are also ordinary black self-tapping screws with a sharp tip at the end, which you just can’t tighten. Before fastening products with their help, you will need to make holes.
Tips for choosing a drill for self-tapping screws
There are two types of self-tapping screws: for wood and for metal bases. For metal surfaces, use a self-tapping screw with a thread that has a small distance between the turns. Thanks to this, the fixation of the elements is reliable. When using fasteners with a diameter of 3.5 mm, no pre-drilling is necessary. If the work involves the use of thin sheet metal, it is necessary to drill holes in advance.
The thickness of the hole being drilled directly depends on the thickness of the material used. Having guessed the size of the drill, you can then screw in the self-tapping screw manually using a regular screwdriver.
Table of recommended drill diameters for a certain metal thickness
| metal thickness, mm | 0,5 | 0,7 | 1,0 | 1,5 | 2,0 | 3,0 | 4,0 |
| drill diameter, mm | — | 3,3 | 3,4 | 3,5 | 3,6 | 3,7 | 3,8 |
Typically, drills with a diameter of 3.4 are used. Other species are also found, but much less frequently.
Fastenings to metal structures: main features
Metal screws are used when you need to securely fix any material to a metal structure. Their caps are hexagonal, hemispherical, with a press washer . Carbon steel is used in the production of such fasteners. In order to extend their service life, when used in rooms with high humidity, they are additionally processed (galvanized).
In order to install it into the metal base, you will need self-tapping screws with a drill. Such fastenings are necessary if the material is more than 0.9 mm thick and no pre-drilling has been carried out.
How to properly screw a self-tapping screw into metal
Fasteners can have heads of different diameters. Therefore, you should get a suitable screwdriver or screwdriver with a suitable attachment. If you plan to tighten only 1-3 screws, then you can get by with a screwdriver. If you are planning a larger-scale job, it is impossible to complete the plan without a screwdriver. This tool will allow you to quickly and efficiently perform all the necessary work.
The general screwing technology is as follows:
- First, you need to determine the type of material, since there is a soft metal - aluminum and there is steel.
- If you have to work with steel, you first need to make holes.
- Install the fastener “in position”. Carefully but firmly, you need to screw it in with a drill until it goes deep and secures into the material. After this, the drill speed can be increased. At the last stage, it is better to reduce the speed to avoid damaging the screw.
- When working with aluminum, you can do without pre-drilling. Screwing is done using a screwdriver.
Source: https://stroitesnami.com/clauses/sverlo-pod-samorezy/
How to choose a drill for a self-tapping screw
Drilling a hole in the wall is only half the battle. To complete the fastening task, you need to screw more screws, directly into the drilled hole or into the dowels.
A self-tapping screw is a type of fastener, which is a rod with a sharp thread and a head designed to transmit torque when screwing while simultaneously cutting threads in the elements being connected.
The range of self-tapping screws for wall mounting on sale tends to be infinite. The task of selecting hardware (from the phrase “metal products”) for fastening to the wall seems insoluble. But if you put everything into detail, it becomes clear what kind of screw is required for each specific case.
Self-tapping screws are made of brass, carbon and stainless steel (the metal contains more than 13% chromium). The most widely used self-tapping screws are made of carbon steel with a protective coating. They are the cheapest.
Carbon steel self-tapping screws are available with the following types of protective coatings. Oxidized, black - for fastening in rooms with normal humidity. Galvanized silver - for indoor and outdoor use. Galvanized, yellow – for indoor and outdoor use. They have a golden decorative appearance. Look good on gold-plated door locks and hinges.
Types and types of self-tapping screws
Depending on the type of thread, there are self-tapping screws: with a universal thread, with a rare thread pitch, and with a frequent one. Self-tapping screws with a frequent thread pitch are designed for screwing into metal sheets. For example, if you need to hang a heavy picture on a plasterboard wall.
Use a powerful magnet to find the place where the profile to which the sheets are screwed is located, and screw the self-tapping screw through the drywall into the profile.
If the screw does not have a drill at the end, then you must first drill a hole in the metal with a diameter equal to the internal diameter of the screw thread.
For fastening sheets of roofing iron, there are special galvanized self-tapping screws of two sizes: 4.8×16 and 4.8×19 with a hex head. A type of self-tapping screws with a rare thread pitch are designed specifically for screwing into soft materials, such as plastic, plaster, asbestos, wooden boards and the like. Universal – designed for screwing into any materials. Of course, it is better to use specially designed ones, but any will hold securely.
A separate line worth noting is the self-tapping screw - a confirmat, specially created for the manufacture of furniture from wood and chipboard. The confirmat type self-tapping screw, with a clean surface and a large area of the lateral surface of the thread, allows you to obtain a high-strength and precise connection of elements. The most popular confirmat size is 7×50. Before screwing the confirmat, a hole with a diameter of 4.5 or 7 mm is required, respectively. The confirmation head is made for a hex key.
To hide the head of a tightened self-tapping screw, Confirmat produces decorative plastic buttons - plugs of any color. The plug with its protrusion is tightly inserted into the hexagonal hole of the confirmation head and disguises it to match the color of the furniture.
It should also be noted that there are self-tapping screws for concrete, which are screwed without a dowel directly into the drilled hole. When screwing into porous material and with cavities, drilling holes with a hammer drill is not allowed. To make it easier to screw, a little bit of any machine oil should be injected into the hole before screwing. Used for permanent fastening. I don’t use them because they are difficult to tighten and even more difficult to unscrew.
There are also self-tapping screws that have a herringbone thread profile. They are driven into the hole at the same time as the dowel with a hammer and are also intended for fastening “forever”. Their use is justified, for example, when attaching a baguette for a suspended ceiling or when installing plastic window frames. Their advantage is the speed of installation.
The head is the extended part of the self-tapping screw, designed to hold fixed objects and ensure the transmission of torque from the tool to the self-tapping screw.
Self-tapping screws are designated as follows: 3×25, where 3 is the outer diameter of the thread (mm), 25 is the length of the self-tapping screw measured from the end of the head to the tip of the rod (mm).
Selecting a self-tapping screw depending on the load
Self-tapping screws have a greater safety margin for shearing and bending. The main thing is to securely fasten it to the wall. The more porous the structure of the wall material, the thicker and longer the dowel should be in order to have a larger engagement area, and accordingly the standard size of the self-tapping screw. If in doubt about the choice, it is better to choose a larger self-tapping screw for fastening.
* – the self-tapping screw is screwed in after installing a special dowel for drywall.
An anchor is a type of finished fastener for securing heavy products by wedging into the wall. Anchor translated from German means anchor. Practically, this is the same dowel and self-tapping screw, but the difference is that the dowel is made of metal, and the self-tapping screw is a bolt or stud with a metric thread that screws into a conical nut.
The conical nut, entering the tubular split base of the anchor, pushes it apart, creating a greater moment of friction with the wall material. The use of anchors is only possible when fastening in very hard materials, dense brick, concrete and stone. In everyday life, such cases may arise when attaching a heavy chandelier to a concrete ceiling or when installing a suspended ceiling of a larger area.
The use of an anchor is justified, for example, for fastening sports equipment in an apartment - rings, wall bars. Children's swings on anchors will also hold securely.
Anchors are expensive and therefore their use is justified only if there is no alternative method of fastening. The anchor is indispensable, for example, when attaching a heavy chandelier to the ceiling. In practice, in many cases, fastening with an anchor can be replaced with fastening with plastic dowels paired with self-tapping screws, increasing their number.
Source: https://respect-kovka.com/kak-podobrat-sverlo-pod-samorez/
5 tips for using wood screws
Wood screws produced by fastener manufacturers these days are hardware specially created for working with wood materials of various densities. Their special design ensures easy screwing and reliable fixation. However, the use of such self-tapping screws requires the master to know some nuances that ensure high quality work and save effort and time.
Tip 1: Pilot holes
Screws produced for working with wood are designed so that they can be screwed directly into the material, without prior preparation. Most often, this fastener is used in this way, using only a screwdriver or screwdriver when performing work. However, there are cases when the use of self-tapping screws puts the workpiece at risk. When fastening thin wooden parts or elements made of strong but brittle wood, there is always a risk of the material splitting.
To avoid damage to the product, it is necessary to prepare a pilot hole before screwing in the screw. This work is performed using a drill and a wood drill bit, the diameter of which is selected depending on the characteristics of the material. If the screw will be screwed into a part made of soft rocks, the diameter of the drill should be 2 times smaller than the diameter of the self-tapping screw. When working with oak and tree species of similar density, use a drill that fully matches the size of the fastener.
Tip 2. Choose the right length
When choosing self-tapping screws by length, many are guided by the opinion that the longer the hardware, the more reliable the fastening will be. If possible, they even use screws that go through the parts being connected. This approach is incorrect - specialists in the field of materials science know that maximum fixation strength is achieved only if the screw is 5-6 mm shorter than the total thickness of the parts being connected.
Tip 3. How to choose the diameter of the screw
When deciding on the diameter of a self-tapping screw for woodworking, many people make the same mistake. It lies in the fact that to connect individual parts, they try to use fasteners with the greatest possible thickness.
It is believed that a screw with a large diameter makes the connection as reliable as possible. This is not entirely true - a long and thin self-tapping screw will do the job much more efficiently than a thick and short one.
In addition, it is more convenient to work with thin products - the chance of splitting the workpiece in this case is significantly reduced.
Tip 4. Cover the screws with wax
It is not at all easy to screw a self-tapping screw into some types of wood, especially if the work is done by hand. To make your job easier, lubricate the screws with beeswax or regular laundry soap. When tightened, these substances will act as a lubricant, greatly facilitating the passage of hardware into the thickness of the material.
Tip 5. Unscrew the old screw
All the advice we provided related to screwing in self-tapping screws. Finally, we will consider removing problematic fasteners from wood. If you need to unscrew an old rusty screw from wood, then the simplest and most material-friendly method is to heat the hardware.
Raise the temperature of the fastener by touching its head with a regular soldering iron. It is known that when heated, a metal expands and then, after a decrease in temperature, returns to its original state.
Temperature changes can disrupt the bond between the corroding metal and the wood, allowing you to easily remove the “complex” self-tapping screw. Sometimes to achieve the desired effect, the procedure needs to be repeated 2-3 times.
Useful tips 09.20.2019 13:32:01
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Source: https://Krepcom.ru/blog/poleznye-sovety/5-sovetov-po-primeneniyu-samorezov-po-derevu/
What drill to use for furniture screws
The main fastening element in furniture assembly is the confirmat. It is screwed in with pre-drilled holes. It is the drilling of assembly holes in chipboard for confirmations that we will consider in this article.
Necessary tool
To assemble the chipboard parts we will need:
- Screwdriver
- Confirmation bat
- Confirm drill
- Ruler or tape measure
- Pencil and awl
- Confirmations
Hole depth and width
When assembling furniture, confirmat size 6.4*50 is usually used. Because the thread diameter is 6.4 mm, and the diameter of the confirmation body is 4.4 mm, then for high-quality fastening of parts, the hole diameter must be in the range of 4.5-5 mm and a depth of at least 50 mm.
If the thickness of the hole is greater than the specified one, the confirmat will not hold the parts well; if it is less, its thickness can tear the chipboard.
For drilling, use a confirmat drill with a diameter of 4.5 mm, which is equipped with an additional head for drilling an enlarged hole for the neck of the confirmat, which also makes a countersink for its head.
Of course, you can use a regular drill with a diameter of 5 mm, but for high-quality fastening in the hole you will additionally need to make space for the neck of the confirmat and its head.
Marking drilling locations
In order to perfectly fasten two parts, it is necessary to mark the places of their fastenings as accurately as possible.
On the part that will be applied to the end (the one on which there will be a through hole), you need to make two measurements - along the length (usually 5-10 cm) and from the edge - exactly 8 mm (this is if the thickness of the plate is 16 mm).
On a part that lies perpendicular, mark the drilling point at the end. Here you need to maintain the same distance in length (5-10 cm from the beginning), and in width - strictly in the center (8 mm from the edge).
Markings must be done as accurately as possible, especially along the length, because If the markings are incorrect, your parts may have extra gaps or protrusions when joined.
It is better to make a through hole in the first part, attach it to the second - and immediately use a drill to mark the drilling location at the end of the second part. And then, separately, calmly drill the hole.
Drilling into the layer of a part
We make a hole at a distance of 8 mm from the edge.
Before making a through hole, place a piece of unnecessary chipboard under the part. This will prevent chips from appearing on the reverse side.
When the through hole is made, the part can be drilled on the fly to drill holes for the neck and head of the confirmat.
Drilling at the end of a part
The main rule is that when drilling at the end, the drill must be strictly perpendicular to the end of the part. If you don't hold the drill straight, the drill bit may go sideways and come out, ruining the part.
Drilling in two parts at the same time
This option is considered the most accurate and, moreover, the fastest. But in order to make a hole in two parts at the same time, you will need to fix them before drilling. To do this, you may need special clamps, clamps and other devices.
Hole Drilling Tools
In order not to mark 8 mm from the edge each time both into the layer and at the end, you can use a special device, which, by the way, is easy to make yourself.
Source: https://moreremonta.info/strojka/kakim-sverlom-sverlit-pod-mebelnyj-samorez/
Roofing screws - dimensions in the table, price and technical characteristics
Modern roofing materials are increasingly replacing the usual slate covering and require the use of special fasteners during their installation. Roofing screws are self-driving screws.
Their main purpose is high-quality fastening of roofing material from sheet metal to the load-bearing structures of wooden or metal roof sheathing.
Specifications
Considering roofing screws (also known as hardware or fasteners), as the section says, we can say that they consist of three parts with different functional purposes. This:
- A drill or drill on the tip of a self-tapping screw , facilitating self-drilling.
- A body with a thread that allows screwing and deepening of fasteners into a sheathing made of wood or metal.
- A cap, or head, used for screwing in a self-tapping screw and further fixing the roofing material.
Due to the specificity of the application, roofing screws are made of durable grades of hydrocarbon steel. Subsequent coating with zinc ensures their protection from corrosive destruction. In addition to galvanized ones, you can find specimens made of “stainless steel” on sale, but their cost is much higher.
As for the shape of the caps, in addition to the standard round shape, self-tapping screws with a shaped hexagonal cap are available for a Phillips screwdriver. It is more convenient to work with such fasteners and therefore it is most popular when installing roofs.
Speaking about sizes, we mean the ratio of the diameter to the length of the product. Regarding roofing screws, the existing range of sizes is quite wide and provides reliable fastening of roofing materials with different profile configurations. Of course, the size also affects the weight of the product.
But the most distinctive feature of this type of fastener is that it is equipped with a special washer. The washer is a combined structure made of metal and rubber, subject to high temperatures.
Having a round shape, it is designed to press the material more tightly against the sheathing while simultaneously sealing the hole under the screw head.
The table below shows some comparative characteristics of the most popular fastener samples:
Well, the last thing, which may not be directly related to technical characteristics. To ensure an aesthetic combination with the roofing material, manufacturers paint the top part and fastener washers in different colors.
Painting, produced by powder paint and varnish mixtures with further firing in muffle furnaces, should retain this most aesthetic appearance for as long as possible. And if paint lags already at the installation stage, this is a sign of low-quality fastening material.
Types of roofing screws
The ability to screw into various types of materials without pre-drilling greatly facilitates and speeds up work processes using roofing fasteners.
But it is necessary to understand that, despite the apparent external similarity, self-tapping screws are structurally different in two main ways:
- designed for screwing into metal structures,
- for fastening roofs to wooden bases.
These are the so-called self-tapping screws for wood and metal. Upon visual inspection, it is not difficult to determine whether they belong to one type or another:
- Firstly, fasteners designed for working with metal are distinguished by a longer drill, with a diameter approximately equal to the body of the screw.
- Secondly, self-tapping screws for metal have a finer thread pitch than samples for woodworking. It must be taken into account that the design of the drills themselves limits the functionality of the fasteners when drilling.
According to the type of drills (drills), fasteners, in turn, are divided into three types: type 1; type 3; type 3.1.
To select the correct fasteners, it is necessary to take into account the thickness of the metal of the sheathing. Incorrectly selected screws will not only create difficulties when installing the roof, but will also not ensure high-quality fastening of the material to the supporting structures.
The larger diameter of the screw body can also be attributed to the distinctive features of fasteners designed for working with metal. This is due to the higher loads placed on the hardware at the moment of screwing into the metal.
When choosing, it is very important not to neglect whether the screws belong to one type or another. It is a common mistake to assume that a screw designed for fastening to metal will be all the more suitable for use on a wooden base.
The fact is that a large drill, when twisted, will break a hole that is too large in a relatively soft tree, which is why the hardware with its threaded part will not fit tightly enough into the body of the wooden structure.
A smaller drill and an increased thread pitch of a wood screw will, at a minimum, create difficulties when screwing it into metal and will not allow for reliable fastening of the material.
Fastening screws
Before we consider some of the nuances of fastening roofing material with self-tapping screws, we should return to a more detailed consideration of the sealing washer. The combined washer greatly affects the quality of roof fastening, which in turn significantly increases the trouble-free service life of the entire structure.
When choosing self-tapping screws, you need to pay special attention to the quality of the cushioning material, which is vulcanized rubber . A structure that is too porous or, on the contrary, rigid indicates poor quality of the fastening element and will not provide sufficient shock absorption of the roofing material under wind loads. Also, failure of the rubber gasket will irreversibly lead to roof leakage in the places where it is attached with self-tapping screws.
The size of the hardware is of no small importance. When choosing self-tapping screws according to length, it should be taken into account that after fully tightening they must enter the body of the wooden sheathing at least 45 mm. And the length of the self-tapping screw extending beyond the metal profile must be at least 5 mm.
, excluding the drilling part.
For roof installation, it is recommended to use a screwdriver with a rotation speed control function.
It is recommended to use a higher speed for drilling holes, and a lower rotation speed of the rotor of the device for cutting threads in a metal profile.
Particular attention must be paid to the screwing force of the hardware. A self-tapping screw that is not tightened tightly enough will not ensure proper pressing of the material against the sheathing, which can lead to its tearing. On the contrary, too-tightened hardware will simply crush the gasket material on the washer, destroying its structure, with the logical consequences that follow.
Also, when screwing in fasteners, strict perpendicularity to the cross-section of the sheathing should be observed. That is, the angle between the screw and the roof plane should be 90 degrees. The slightest distortions will also lead to annoying consequences in the form of roof leaks and material breakage under wind loads.
Cost of roofing screws
Considering the technical characteristics and scope of application, it would be unfair not to dwell on the issue of the cost of this fastening material.
The main components that form the cost of certain commodity and material assets offered to consumers on the goods market are standard:
- Product quality;
- Manufacturer's name (brand);
- Product functionality;
- And, of course, consumer demand.
It is naive to believe that roofing screws are any different from these requirements. To the above we can only add the consumption of material required for production. That is, the larger the screw, the correspondingly higher its cost.
The table below shows comparative prices for the well-known brand of “Gunnebo” products with a washer and EPDM gasket in the Moscow region:
Choosing roofing screws
Well, summing up the information presented above, it is logical to dwell on the issue of the correct choice of fastening material.
The first thing to consider when choosing is, of course, the sheathing material to which the roof will be attached. The type of self-tapping screws purchased must comply with the work regulations.
The second requirement is the size of the hardware. Above in the text there is a paragraph indicating the minimum sizes. It is possible to use longer copies, but you will have to overpay a certain amount, since the price directly depends on the size of the material.
If you have decided to buy more expensive, so-called branded products from well-known manufacturers, you should pay attention to the hex head. Well-known manufacturers always brand their products with engraving on the top end of the cap. And if the seller claims that this is an exclusively branded product, but simply forgot to put a stamp, do not give in to his persuasion under any circumstances.
The next point is the anti-corrosion zinc coating. Roofing screws are sold in original packaging. Ask the seller to show it to study information about the technical characteristics of the product. Among the various information texts provided by the manufacturer, try to find information about the thickness of the zinc coating on the screws.
You should refuse to purchase if the thickness of the zinc coating is less than 12 microns.
Blitz advice
In conclusion, we can give advice on checking the quality of self-tapping screws in so-called field conditions. If the seller confidently convinces you of the high quality of the product, ask him to sacrifice one washer with a rubber gasket.
It is necessary to place the washer end-to-end between the jaws of the pliers and squeeze it. If the paint or zinc coating has not peeled off the washer and the gasket has not peeled off, you can safely purchase fasteners; they are of high quality.
Source: https://orcmaster.com/instruments/samorezy-krovelnye.html
How to choose the correct drill size for a dowel
Today there is no need to use nails to hang a picture, shelf, cabinet or other piece of furniture and decor. Firstly, it is inconvenient, and secondly, it is unreliable.
Any fastener must be reliable; it is better to choose dowels that are installed in a pre-drilled hole.
The reliability of such fastening directly depends on the correctly selected drill; the smaller the difference in the diameter of the hole and the rod, the stronger it will be installed. We’ll figure out how to choose a drill for a dowel further.
Basic selection principles
The correct choice of drill for the dowel should be based on the following:
- When calculating which hole to drill for the dowel, it is worth considering the type of wall into which the rod is installed and what it is covered with.
- Weight of attached furniture and maximum possible loads.
Considering the above parameters, you can choose the appropriate tool correctly. To make it easier, you need to take into account the factory size of the drill and fasteners, as well as the tensile strength of the dowel. There are markings on the tool, based on which it is easy to select the desired model.
If the wall material is very strong, for example concrete, you should choose two types of drills and different operating modes of the drill. To begin with, you should take a drill several sizes smaller than the dowels, switch the drill to impact mode and make the necessary hole. Then, using a gimlet of identical size with fasteners, in normal mode, bring the hole to the required parameters.
With the help of such manipulations, you can carry out work faster, do not overload the drill, get an ideally shaped hole and maintain the integrity of the wall and its coating. The rod in the hole should not rotate and move freely in it. Instead of a drill, it is better to choose a hammer drill, as it is more powerful and productive.
If the wall material is loose, it is better that the drill size is several sizes smaller than the rod (for example, for an 8 dowel, a drill size 6 or 7). This will allow the fasteners to be installed tightly, even in the event of excessive destruction of the wall structure.
When choosing the type of drill, you should pay attention to pobedit ones, given their high strength and durability.
The length of the hole should be several millimeters longer than the length of the dowel. This is necessary to ensure that it fits tightly into the niche over its entire length, since dust can accumulate in the hole.
Fastening shelves, pictures and other light objects does not require special preparation or the presence of a powerful tool. All you need is a power tool, a simple dowel and a suitable drill bit for the dowel.
This type of fastener is excellent for concrete and brick walls. It can also be mounted in the ceiling, for which you need to make a hole for dowel 6. Size 4 fasteners are suitable for walls. For walls of this type, a pobedit tip is best suited.
In most cases, two mounting points will be sufficient.
Fastening medium-weight products
If the weight of the mounted decorative element exceeds 5 kg, more reliable fasteners are needed. A dowel with a diameter of 8 mm is suitable and, accordingly, the drill diameter is also 8 mm. A hole length of 6 cm is quite enough when working with ordinary walls; when working with loose material or a ceiling, the depth is increased to 8.
If the weight of an object approaches 10 kg, for reliability it is worth installing 4 fasteners, since 2 may not hold it. It is better to use a hammer drill as a tool.
Securing heavy objects
Heavy furniture or household appliances that are mounted on the wall carry significant physical stress. Even if the fastener looks reliable at first, it can fail over time. Installation of heavy objects should only be carried out on walls made of durable materials, concrete or brick.
Loose material can collapse under the influence of heavy weight. The normal diameter of the fastener is 10 mm, and the depth of the hole is more than 6 cm; you need to rely on these indicators to determine the diameter of the drill. For reliability, the number of mounting points is recommended to be at least 6.
When choosing which drill to drill with, you can safely choose victorious ones.
To ensure that the attached structure can withstand about 100 kg, it is better to use anchor bolts.
They are more reliable, even given their smaller size. You should make a hole up to 6 cm deep and install the selected bolt.
There are 3 types:
- A bolt with an outer nut that is tightened with a regular wrench.
- Self-locking nut that can be tightened with a screwdriver.
- Double-expansion anchors, which are used for fastening the most massive furniture.
Attaching to an unstable surface
Modern houses have many surfaces made of not very durable materials. These include drywall, old brick, wooden boards or slabs of pressed sawdust. When working with them, it is better to use nylon fasteners with a diameter of more than 10 mm; the installation depth should not be less than 6 cm. It is better to choose a gimlet that is several sizes smaller.
The drilling process should be shock-free, as excessive load can damage the surface. Using the impact mode may not leave visible damage, but the internal structure of the wall may be damaged. If the diameter of the drill is too large, the fasteners will move freely in the hole, gradually increasing its diameter, especially if the work was carried out with aerated concrete.
For plasterboard walls, it is not necessary to use a drill of a smaller diameter, the main thing is not to put pressure on the drill and not to use the impact mode. Drywall is a very delicate material, even a small load can lead to the destruction of a section of the wall. Drill the hole with light force so that it matches the size of the plastic dowel with self-tapping screw.
It is worth understanding that there is no need to attach heavy structures to such surfaces, even if the material initially copes with the load, over time, collapse may occur under heavy weight.
If you take into account the material from which the wall is made, choose the right dowel and drill for it, and also have a high-quality tool on hand, you can make a high-quality installation and not worry about the safety of your furniture or household appliances. By following the recommendations, even an inexperienced craftsman can handle such installation.
Source: https://stankiexpert.ru/tehnologii/kak-podobrat-sverlo-pod-dyubel.html
Why drill holes for self-tapping screws or how to easily screw in a self-tapping screw
Unlike nails, which fasten wooden parts by compressing the nail shaft with wood, screws and self-tapping screws have a screw thread. This same thread does not allow the screw or self-tapping screw to freely exit the body of the wood, and in addition, the thread significantly increases the contact area of the screw or self-tapping screw with the wood.
Therefore, even if you drill a hole of the same diameter as a self-tapping screw, the load-bearing capacity of the screwed-in self-tapping screw will, of course, decrease slightly, but at the same time, the internal stresses in the wood after tightening the self-tapping screw will also decrease much more, which means it will be much easier to tighten the self-tapping screw and the risk of splitting the wood , chipboard or other material will be significantly reduced.
2
The process of wood deformation under the influence of force when tightening a self-tapping screw is very complex. Wood is a heterogeneous material and the strength of wood very much depends on the point at which the load is applied, the presence of knots, the type of wood, etc.
Wood has minimal strength at the junction of the fibers, so usually the tip of the self-tapping screw falls between the fibers of the wood, and it is almost impossible to tighten the self-tapping screw, as well as drill a hole in the wood with an accuracy of tenths of a millimeter. Fortunately, there is usually no such need.
For household purposes, an error of 0.5-1.5 mm is quite normal.
3
Any screw or self-tapping screw has a certain volume, and when we screw a screw or screw into wood, we are thereby trying to reduce the volume of wood by the volume of the screw. No miracle happens. The volume of wood is partially reduced due to wood collapse, i.e. due to inelastic deformations.
Moreover, the duller the screw or self-tapping screw (and self-tapping screws can also be dull), the greater the proportion of inelastic deformations that occur under the tip of the screw, which means that you need to apply more pressure on the self-tapping screw or self-tapping screw to produce these deformations. Part of the volume is released due to splitting of wood along the fibers, while a gap appears between the fibers, or, scientifically speaking, a crack.
The width of the crack opening depends not only on the factors listed in paragraph 2, but also on the geometric dimensions of the product and the point of application of the load. The larger the geometric parameters of the product and the closer the point of screwing in the self-tapping screw to the center of gravity of the section, the smaller the width of the crack opening, and this means, again, more effort must be applied to tighten the self-tapping screw or screw in such a place.
And the smaller the width and height of the product and the closer the place where the screw is screwed in is to the edge, the greater the likelihood that the product will not just crack, but also split, and then it will be very easy to tighten the screw or screw, but there will be no benefit from such a self-tapping screw or screw, but only one complete harm. The remaining volume for the screw to be screwed in is released due to elastic deformations.
The distribution of internal stresses in the body of wood during elastic deformations leads to the appearance of cracks. A similar situation is observed when screwing self-tapping screws into small chipboard or OSB parts; particle boards or oriented strand boards have less strength than wood.
4.a
Thus, when we screw a screw or self-tapping screw into wood without preliminary drilling, we must constantly overcome the strength limit of the wood under the tip of the self-tapping screw or screw and at the turns of the thread and the ever-increasing frictional force that arises due to the compression of the self-tapping screw by the wood. The friction force increases due to an increase in the contact area of the self-tapping screw or screw with the wood.
As a result, with sufficiently large rod diameters or when screwing into harder types of wood or to greater depths, no normal screwdriver will have enough power to tighten a screw or self-tapping screw to the required depth.
And the screwdriver will only chirp loudly, hinting that the strength limit has been exceeded and this is correct, because screwdriver manufacturers do not like to repair products damaged due to the stubbornness of the user for free.
4.b
However, not all people use a screwdriver that has power adjustment; why buy an extra power tool when you have a drill and a screwdriver attachment for self-tapping screws. A drill, unlike screwdrivers, does not have power adjustment, and therefore when tightening self-tapping screws or screws of large diameter or to great depth, 4 scenarios are possible:
- You will break the slots on the head of a self-tapping screw or screw - a very high probability, especially when tightening at high speeds.
- You will very quickly ruin the screwdriver attachment. However, if the nozzle for self-tapping screws is Chinese, this can also happen with relatively small loads on the nozzle.
- You will break a self-tapping screw that cannot withstand the torque - not often, but it happens. The fact is that self-tapping screws, unlike screws, are pre-hardened and therefore more fragile than screws.
- You will burn the drill when tightening a large number of screws at low speeds.
I don’t think you will like at least one of these options, so it’s better to spend extra time drilling holes than to spend this time repairing the drill, buying new attachments, or unscrewing a broken screw.
4.c
Despite the victorious march of electricity across the globe, the effect of brute physical force has not yet been canceled, and therefore even now it is not uncommon for screws or self-tapping screws to be tightened manually with a screwdriver. But to be honest, I myself don’t like having to go down and get a power tool when I’m working at height.
When tightening screws or self-tapping screws by hand, the scenarios are almost the same as when working with a drill, only you won’t burn the drill, but instead of the attachment you will ruin the screwdriver and you can still get a couple of good calluses.
But there is a positive side to this - your muscles will develop, and girls love it, just don’t tell them exactly how you pumped up your muscles.
4.g
There is another method that is now little used - do not tighten screws or self-tapping screws, but hammer them in. However, this method is more suitable for screws; self-tapping screws, due to their increased fragility, more often break than bend, and only if the self-tapping screw sticks out 0.3-0.5 cm above the surface of the wood, then you can try to finish it off. We are not talking about special screws driven into dowels here.
In Soviet times, there were other recommendations for tightening screws (there was a lot of cheap electricity back then, but for some reason there were few available power tools), for example, it was proposed to first tighten the first screw until the slots were licked, then unscrew and throw away the first screw and screw the second one in its place , and if the slots on the second one stick together, then unscrew the second screw and screw the third one in its place. Another option was more gentle; it was proposed to lubricate the screw with soap before tightening it to reduce the friction force of the screw shaft on the wood. Nowadays, such methods of screwing in a screw seem exotic, however, the choice of method is yours.
Sometimes it is also necessary to drill holes for metal screws if the screws are blunt. This is especially often done when assembling a metal frame for plasterboard, plastic panels or MDF panels.
The fact is that blunt screws do not cut through the tin of the frame, but push through and, accordingly, the contact area of the screw increases even more and you need to press very hard on such a screw.
In this case, drilling holes will not only facilitate and speed up the assembly of the frame, but will also help to avoid unnecessary injuries, because it is very easy to damage your hand if a nozzle comes off a screw.
Source: http://DoctorLom.com/item231.html
Screw hole size
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Self-tapping drill diameter
It is difficult to do without self-tapping screws in almost any area of construction and repair. For example, it is difficult to hang the same shelves, pictures, cabinets without using self-tapping screws. The screws themselves are divided by type (for certain materials).
Diameter of drill for metal self-tapping screw
If the metal that needs to be drilled or screwed into metal is less than 0.5 millimeters thick, then there are no problems, you don’t even need to pre-drill it. But if the metal thickness is greater, for example 0.8 millimeters or 1 millimeter, then you must first drill a hole for installing a self-tapping screw. Typically, the thickness of the hole being drilled depends on the thickness of the material. If you guess the size of the drill, then you can tighten the self-tapping screw even with a regular screwdriver.
Below is a table of recommended drill diameters for a certain metal thickness.
The most common drill diameter is 3.4, the others are less common.
In the case of self-tapping screws (+ press washer) up to 1.5 mm of metal thickness, you don’t have to drill a hole, but above that you can’t do without it, since the drill itself made from a self-tapping screw can’t do the job, it’s almost useless.
Correspondence table between drill diameters for sharp self-tapping screws and metal thickness
The table data may change a lot due to:
- The quality of the material itself;
- Quality of self-tapping screws;
- Screwdriver power;
- What kind of reliability is needed for fastening?
So, in general, if you have thick, dense wood or a thick sheet of metal, you first need to drill it (smaller in diameter than the diameter of the screw) and then screw it in.
Installation conditions and diameters of preliminary holes for self-tapping screws BEST-Fixtures
Experienced craftsmen also remember those times when several self-tapping screws were used at once to create just one fastening using a self-tapping screw! The installation method was simple, but required a mandatory technological sequence. The first screw was screwed in 2/3 of its length and, to avoid licking the slot on the head, was unscrewed and thrown out.
The second was to cut a thread in the base to the full depth of the fastening and again, unscrew it and throw it away. The concerns were quite serious - the licked slot on the head of the screw prevents its unhindered unscrewing if necessary (Fig. 7). Those. The first two self-tapping screws served as a kind of tap - a tool for cutting threads.
And only the last, third, screw served its intended purpose: to form a threaded fastener. In everyday life, they often avoided the advice of “experienced” people and, applying considerable pressure on a screwdriver, screwed a self-tapping screw into the base. In this case, the slot on the head was indeed damaged, but with sufficient effort this did not interfere with installing the self-tapping screw in the designed position.
As a result: after 2-3 years of use, even indoors, the hardware sometimes became covered with rust and when replacing it, it was almost impossible to unscrew them without the help of pliers and a drill.
Source: https://moy-instrument.ru/podelki/razmer-otverstiya-pod-samorez.html
Self-tapping drill diameter
It is difficult to do without self-tapping screws in almost any area of construction and repair. For example, it is difficult to hang the same shelves, pictures, cabinets without using self-tapping screws. The screws themselves are divided by type (for certain materials).
Diameter of drill for self-tapping screws for metal table
- 1 Dimensions of self-tapping screws for metal with and without a drill, their characteristics
- 2 Self-tapping screws for metal: 70 photos, design features and the best ideas for use
- 3 Self-tapping screws for metal, dimensions table. Self-tapping screws with drill. Outer diameter mm
- 4 Self-tapping screw for metal with a press washer: types, technical characteristics and dimensions
- 5 Differences between different types of screws: metal fasteners with and without a drill
The strength and durability of the entire structure depends on the choice of hardware, or fasteners, as any builder will tell you. One of the types of such fasteners are self-tapping screws.
Their feature is that there is no need to cut threads to connect elements. In cases with self-tapping screws for metal, there is a tip option with a drill for thick-walled metal, profile pipe, angle, etc., or a sharp tip for thin or sheet metal, such as roofing.
Types of screws for metal
A self-tapping screw for metal can have an edge either in the form of a threaded tip or in the form of a drill. In addition, they are divided into several types:
- roofing screws,
- for fastening metal sheets up to 0.9 mm thick,
- for fastening metal sheets up to 2.0 mm thick,
- for drywall,
- for fastening gypsum fiber boards.
Each of these types has its own characteristics: thickness, length, thread width, head profile, tip type, metal grade. All characteristics are selected based on the area of application of this hardware and the force it must withstand.
Types by tip type
Self-tapping screws for metal have two types of tips: a sharp tip with a thread and a tip with a drill. They are used for fastening sheets of different thicknesses.
Self-tapping screw with a sharp tip, dimensions and characteristics
Self-tapping screw for metal with a sharp tip
This type of hardware has a pointed tip with a knurled thread. Used for fastening metal up to 0.9 mm thick. Can be used to attach elements to metal or plastic. For fastening to wood, self-tapping screws with a sharp tip and a large thread pitch are used. The head can be equipped with a press washer (including a painted one) or without it.
If it is necessary to install metal with a thickness of more than 0.9 mm using these types of hardware, it is necessary to first drill a hole at the joint. It is recommended to use a drill 3.2-3.5 mm in diameter.
Table 1. Dimensions of roofing screws for metal with a sharp tip
| 4,2×13 | 13,0 | 7,1 | 10,6 – 11,4 | 3,2 | 4,05 – 4,3 | 1,66 |
| 4,2×14 | 14,0 | 1,73 | ||||
| 4,2×16 | 16,0 | 1,89 | ||||
| 4,2×19 | 19,0 | 2,04 | ||||
| 4,2×25 | 25,0 | 2,45 | ||||
| 4,2×32 | 32,0 | 2,87 | ||||
| 4,2×41 | 41,0 | 3,60 | ||||
| 4,2×48 | 48,0 | 3,78 | ||||
| 4,2×51 | 51,0 | 3,87 |
Self-tapping screws with drill, dimensions and characteristics
Self-tapping screw for metal with drill
This type of fastener has a tip in the form of a drill with 2 feathers. Used for fastening metal up to 2 mm thick. Can be used to attach elements to metal or plastic. Suitable for interior and exterior work.
It can be either galvanized or with a painted head. The head can be equipped with a press washer.
Powder paint is used for painting; all colors are available according to the RAL table. However, in terms of their qualities, especially for outdoor work, galvanized ones are more durable.
Table 2. Dimensions of roofing screws for metal with a drill
| 4,2×13 | 13,0 | 7,1 | 10,6 – 11,4 | 3,2 | 4,08 – 4,22 | 4,5-5,8 | 3,35-3,5 | 1,85 |
| 4,2×14 | 14,0 | 1,87 | ||||||
| 4,2×16 | 16,0 | 2,05 | ||||||
| 4,2×19 | 19,0 | 2,26 | ||||||
| 4,2×25 | 25,0 | 2,61 | ||||||
| 4,2×32 | 32,0 | 3,05 | ||||||
| 4,2×41 | 41,0 | 3,71 | ||||||
| 4,2×51 | 51,0 | 4,10 |
Why is it important to choose the correct screw size?
Here it is important to adhere to several basic rules:
- The length of the threaded part should not be less than the total thickness of the elements being connected; in other words, the self-tapping screw must go through.
- Using longer fasteners is not rational from an economic point of view. The price of a metal screw directly depends on its length. It is enough if only the tip with the drill goes through.
- When using a large number of these fasteners, it is worth understanding that longer screws also have more weight, for example, a 13 mm screw weighs 1.85 grams, and already a 25 mm screw weighs 2.61 g. In a single value this is not so much, but if hardware is used hundreds of thousands, this will significantly increase the overall weight of the structure. which may be important in certain cases.
Types of self-tapping screws by quality, coating
In total, several types can be distinguished based on the quality of these fasteners:
- galvanized black metal,
- black painted metal,
- black metal without additional coating,
- non-ferrous metal.
Galvanized self-tapping screws are used for outdoor work in places with high humidity.
Painted ones are also used for exterior work, but they are less durable than galvanized ones.
Uncoated self-tapping screws are used for interior work. They can be used for outdoor work, but their service life will be significantly lower than others.
Hardware made of non-ferrous metals is used extremely rarely in construction. This is due to their price. their main area of application is fastening decorative finishing elements. Can be used both for external and internal work.
GOST screws for metal
These products must strictly comply with the following standards: GOST 1144-80 , 1145-80 , 1146-80 , as well as DIN 7981 , 7982 , 7983 where the tip is made in the form of a drill and ISO 7049. These standards are determined by the requirement for the quality of connection of elements for external and internal works.
Steel grade C1018 is used for manufacturing.
Source: http://ooo-asteko.ru/diametr-sverla-pod-samorez-po-metallu-tablitsa/
Holes for metal screws table
· 09.09.2019
All about construction and renovation
Everyone has done renovations at some point or are planning one in the near future. And usually you can’t do without self-tapping screws, since they are considered an excellent fastening material for use on various surfaces. This could be wood, drywall, or one of the metal versions.
Features of using self-tapping screws for metal
Fastening elements that are designed to work with metal have a number of features:
- Resistance to the negative influence of external factors;
- Affordable price;
- High wear resistance;
- Long service life;
- Easy installation;
- High quality.
Metal self-tapping screws are used in many fastenings of metal structures, organization of industrial and production facilities and in many other areas. At the same time, both a specialist and a beginner in this field will be able to perform fastening.
With the right choice of products, they will be practical, easy to use and highly durable. Even after a long period of time, these connecting elements retain their original appearance and reliability of fastening.
Self-tapping material
- Carbon steel is an alloy of iron and carbon without any impurities. It is characterized by increased strength.
- Stainless steel – steel with a chromium content of at least 10.5%, which makes it corrosion-resistant and very durable; stainless steel self-tapping screws will never rust and have an almost unlimited service life, in addition, they are the cheapest.
Stainless steel products also have hygienic properties, which allows them to be used even in medicine.
- Brass is a copper alloy with the addition of zinc, sometimes tin, nickel, lead, manganese or iron. Brass self-tapping screws have proven themselves to be very reliable and wear-resistant.
In addition, brass is non-magnetic, anti-corrosion and resistant to low temperatures.
Self-tapping screw coating
- Phosphated (black) self-tapping screws are made of carbon steel and then treated with phosphates. Used in rooms with high humidity.
- Oxidized (black color). These self-tapping screws are made of carbon steel with a protective oxide film applied. Suitable for use in rooms with normal humidity.
- Galvanized tapping screws are also made from carbon steel, followed by a zinc coating. Suitable for use both indoors and outdoors.
- Galvanized yellow self-tapping screws differ from the previous ones only in color; they are used mainly for door hinges of decorative gold color, since they are visually less noticeable against their background.
- Without cover.
Used for interior work at normal humidity.
