Set Screw: what it is and applications

set screw or stud

There are many screw types on the market, some quite popular and others a bit more exotic for certain specific applications. One of those types is the so called set screw or stud, 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.

The screw is a very genuine type of screw that is used in some practical applications that I’m sure you have seen on some occasions. For example, the first thing that comes to mind now is in the beacons or streetlights, where they are usually used to hold certain parts of these lights when they come dismantled

Differentiating between bolt and screw is not easy for many. The distinction between the two can be confusing, but the main difference lies in the thread and size. Bolts tend to be larger and without a pointed end. Screws are smaller and have pointed ends.

What’s a set screw?

A stud bolt is basically a metal cylinder or threaded rod that has the thread engraved on its entire length. In other words, it lacks a head like other screws. The only difference between its ends is that one of them is called a root and will be screwed into a threaded hole and the other end is usually engraved with a grimace 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 fixing of parts 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 it in place.

The differences between a stud and a traditional stud lie mainly in its physiognomy and the forces to which it is subjected. In a traditional one, you have surely seen that you are threading progressively, but its head (especially if it is made of brass, aluminium or another soft alloy, and very especially when some drills are used without control) can deteriorate due to the force exerted. This makes it impossible to remove it or to continue tightening it…

In the grub screw, the part where the door is exercised is fully integrated into the screw itself, without a head. It is therefore only subjected to one pull. In addition, they are usually made of steel for greater strength.

Types of screws

There are several types of screws beyond the stud, and they can be catalogued according to various factors…

Philips, grub screw

According to the screw head

According to the shape of the screw head there are:

  • Hexagonal: it is quite common and is usually used for fastening or assembly of pressure parts. They usually also have a nut. And not all can be tightened using a wrench or pipe wrench, some also include screwdriver bits. For example, the flange hex screw usually has a star head, and its biggest advantage is that it does not need a washer.
  • Slotted head: these are the most common ones, which allow the use of a screwdriver. There are those with flat slot, cruciform, etc. They are ideal for when no great tightening is 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, to fix 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 great tightening with tightness. I take this opportunity to describe the types of head:
    • Flat: they have a single 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 it has a deeper cross and another superficial mark that gives the appearance of an asterisk.
    • Torx: they are not frequent, but they can be used in some carpentry applications, etc. Its head has a hole in the shape of a star that is not very common.
    • Others: there are others such as goblet or cup, Robertson, Tri-Wing, Torq-Setm, Spanner, etc.
  • Butterfly: as its name indicates it has a kind of nut with “wings” in the shape of a butterfly to be able to tighten it with your own hands. For cases where not too much tightening is needed and they need to be assembled and disassembled frequently.

Depending on the material of the screw

types of screws

On the other hand, if you look at the screw material we have:

  • Aluminum: not too resistant to stress, but resistant to weather and light conditions. Ideal for plastic and wood.
  • Duraluminium: made of aluminium combined with other metals such as chrome. They make their durability increase.
  • Steel: usually stainless steel, and they are very robust.
  • Plastic: they are rare, but there are some to resist well extreme conditions of humidity, such as plumbing applications.
  • Brass: they have a golden color and are very common for use with wood. They are resistant, but not as much as steel.

Depending on the finish

finish grub screw

These screws can also have different finishes:

  • Cadmium: they have a silvery appearance, have a good resistance to different conditions and when oxidized do not generate products derived from corrosion.
  • Galvanized: a zinc bath is used and it also presents a silvery appearance, although the typical zinc stains can be observed. It resists well to corrosion conditions.
  • Tropicalized: they have an iridescent yellow tone. It is achieved with a galvanized and chrome finish. This further increases the resistance to corrosion.
  • Nickel plated: has a bright golden finish thanks to the nickel finish. It is usually used in decorative finishes.
  • Brass: Brass is used and has a shiny metallic look for some decorative finishes and corrosion resistance.
  • Phosphatized: they are bathed in phosphoric acid by immersion and this gives them a grayish black appearance.
  • Bluing: they are semi-gloss with an intense black color. They undergo controlled oxidation of the steel that produces that black layer that makes them more resistant to corrosion.
  • Painted: some are painted to be more decorative, for example the black screws used by some wooden furniture.

Depending on the function

funcion tornillo prisionero

According to the function of the screws can also be catalogued in

  • Self-tapping and self-drilling: used for sheet metal and hardwoods They are pointed and able to make their own way through the material.
  • Wooden threads: unlike the previous ones, they do not have a thread carved in its entire length, but have part of the screw without being carved. They are the typical wood screws where the thread is only 3/4 of the screw. They also have a sharp point and can make their own way.
  • With nut: they have no tip, and use a nut to join parts with great pressure. They can also be used with a mounting washer, reinforcing the seating of nuts and heads.
  • Set screw or studs: (the one described above)
  • Inviolable: this is a type of screw for safety 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 (they are marked with the initials TR on the head), etc.

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