There are a lot of screw types on the market, some quite popular and others somewhat more exotic, special for certain specific applications. One of those types is the so-called set screw, to which we will dedicate this article to describe everything you need to know about this variety and how it can help you with your DIY projects.
El set screw It is a very genuine type of screw that is used in some practical applications that you have surely seen on occasion. For example, the first thing that comes to mind now is the beacons or street lamps, where they are usually used to hold certain parts of these lights when they are disassembled ...
Differentiating between bolt and screw is not an easy thing for many. The distinction between the two can be confusing, but the main difference lies in the thread and the size. Bolts are usually larger and without a pointed end. The screws are smaller and pointed.
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What is a set screw?
Un set screw It is basically a metal cylinder or threaded rod that has the thread engraved throughout its length. That is, it lacks a head as with other screws. The only difference between its ends is that one of them is called the root and it will be screwed into a threaded hole and the other end usually has a groove engraved to fit the screwdriver (it could also be an Allen key) to screw or unscrew.
The usefulness of this type of screw is usually the part fixation and positioning of certain fixed elements in removable objects. For example, imagine a section of a tube that goes into another tube. The outer tube has threaded holes into which these screws can be inserted to exert pressure around the inner tube, thus holding the inner tube.
The differences between a set screw and a traditional one it resides mainly in its physiognomy and the forces to which it is subjected. In a traditional one, you have surely seen that you are tapping progressively, but its head (especially if it is made of brass, aluminum or another soft alloy, and especially when some drills are used without control) can deteriorate due to the force exerted. That makes it impossible to withdraw it or keep squeezing it ...
In the set screw, the part in which the door is exerted is fully integrated into the screw itself, without a head. Therefore, it is only only subjected to traction. In addition, they are usually made of steel for greater resistance.
Types of screws
Several types of screws beyond the set screw, and can be classified according to various factors ...
According to the head
According to the shape of the head of the screw there are:
- Hexagonal: It is quite common and is often used for fastening or mounting of pressure parts. They also usually have a nut. And not all of them can be tightened using a socket or wrench, some also include screwdriver grips. For example, the hex flange screw usually has a star head, and its biggest advantage is that it does not require a washer.
- Slotted head: they are the most common, those that allow the use of a screwdriver. There are them with a flat groove, cruciform, etc. They are ideal for when a great tightening is not needed, such as with wooden elements. In any case, the head remains outside, although if a countersink is made it can be hidden.
- Square head: they are not as frequent as the previous ones. They are used in cases where a great tightening is needed such as hexagonal ones. For example, for fixing cutting tools or moving parts of some machines.
- Cylindrical or round head: they usually have a hexagon inside to insert an Allen key or other type. They are used in joints that need heavy tightening with tightness. I take this opportunity to describe the types of head:
- Plana- They have only one slot in their head for this type of flat screwdriver.
- Star or cross: they are the so-called Phillips type.
- Pozidriv (Pz): very similar to the previous one, but has a deeper cross and another superficial mark that gives the appearance of an asterisk.
- Torx- These are not common, but can be used in some woodworking applications, etc. Its head has a rare star-shaped recess.
- Others: there are others such as glass or cup, Robertson, Tri-Wing, Torq-Setm, Spanner, etc.
- Butterfly: as its name suggests it has a kind of nut with "wings" in the shape of a butterfly to be able to tighten with your own hands. For cases where too much torque is not needed and that need to be mounted and removed frequently.
According to the screw material
On the other hand, if the screw material we have:
- Of aluminum: not too resistant to efforts, but resistant to climatic conditions and light. Ideal for plastic and wood.
- Duralumin: they are made of aluminum combined with other metals such as chromium. They increase its durability.
- Maple: it is usually stainless steel, and they are very robust.
- Plastic- These are rare, but are available to withstand extreme humidity conditions well, such as plumbing applications.
- Brass: They have a golden color and are very common for use with wood. They are strong, but not as strong as steel ones.
According to finishes
These screws may also have different finishes:
- Cadmium: they have a silver appearance, they have good resistance to different conditions and when it oxidizes it does not generate products derived from corrosion.
- Galvanized: a zinc bath is used and it also has a silver appearance, although the typical zinc stains can be observed. It resists well to corrosion conditions.
- Tropicalized: they have an iridescent yellow hue. It is achieved with a galvanized and chrome finish. This further increases the corrosion resistance.
- Nickel plated: Has a shiny gold finish thanks to the nickel finish. It is usually used in decorative finishes.
- Brass plated- Brass is used and has a shiny metallic appearance for some decorative finishes and corrosion resistance.
- Phosphatized: they are bathed in phosphoric acid by immersion and that gives them a grayish black appearance.
- Bluing: they are semi-glossy with a deep black color. They undergo controlled oxidation of the steel that produces that black layer that makes them more resistant to corrosion.
- PaintedSome are painted to be more decorative, for example the black screws used by some wooden furniture.
According to the function
According to The of the screws can also be cataloged in:
- Self-tapping and self-drilling- Used for sheet metal and hardwood. They are sharp and capable of cutting their own path through the material.
- Wood thread: unlike the previous ones, they do not have a thread carved along their entire length, but rather have part of the screw unworked. They are the typical lag screw for wood where the thread is only 3/4 of the screw. They also have a sharp point and can cut their own way.
- With nut: They have no point, and use a nut to join parts with great pressure. It can also be used with a mounting washer, thus reinforcing the seating of nuts and heads.
- Set screw or studs: (the one described above)
- Inviolable: It is a type of screw for security applications that has been screwed in and is impossible to remove. You can only force the part to break. They are used for parts exposed to the public, preventing them from being manipulated.
- Others: they can also be calibrated for higher precision applications, high resistance (marked with the initials TR on the head), etc.