Turn on a screw

We encounter screws everywhere in everyday life. Not only those without manual experience are often in front of a screw and then do not know in which direction they should turn it. Here we do not just explain how to turn on a screw. You will also learn some tips and tricks on how to solve a stuck screw.

These screws are needed

Screwing is probably the most popular method of connecting different components together. The screw is also used to loosely connect objects; for example, when a screw with a dowel is fixed in the wall to hang something like a picture.

Distinguishing features of screws

However, screws are usually used to make firm connections. Screws are made from a variety of materials, the most common being metal alloys and plastics. The simplest distinction is still made after the thread. The main thread:

  • metric threads (fine and standard threads)
  • Coarse thread (wood screws, tapping screws, etc.)

Metric threads are on a cylindrical bolt. The screw shank for a coarse thread, however, is conical, so tapered.

Metric threads on screws

Metric threads also require a mating thread. The mating thread is provided either via a nut or through a thread cut into the bore. The norm for unscrewing the screw is to the left. A screw thread is named after the direction of rotation with which it is tightened. If a (conventional) screw is turned on the left, it is a right-hand thread.

The left-hand thread of metric screws

Opposite is the left-hand thread. Here the screw is screwed in for fixing to the left. If you have an experienced eye, you can also see the direction of rotation based on the thread. Metal screws often have a small slot on the side of the screw head or on the nut where two sides of the hexagon converge if it is a left-hand thread. Left-hand threads are always the exception.

Left-hand threads are mainly used for safety reasons. For example, on gas cylinders whose main valve is provided with a left-hand thread. However, left-hand threads are also used on moving parts that turn around their own axis, for example. A typical example is wheel bolts.

On the passenger side, the wheel bolts or wheel nuts on certain vehicles were always provided with a left-hand thread. Thus, it was to be prevented that a screw or a bolt could inadvertently be loosened by the main turning to the right. Here, too, find the appropriate markers, but not mandatory.

Metric fine and standard thread, inch thread

In addition to left- and right-hand threads, standard and fine threads are also distinguished. In addition to the metric threads there are of course still inch threads, but these are mainly distributed in Anglo-American area. Fine threads are characterized by a very firm hold, because more thread engages. In addition, the thread pitch is still divided.

Coarse thread screws

These are the screws, whose shank converges pointedly. The thread is much deeper, so it extends further out of the shaft. The reason is that these screws have to cut their own thread into the workpiece. This is not always possible without help. So it may well be that screw mounting holes must be pre-drilled. However, with a much smaller drill.

Turn on a screw

Screws are also equipped with different heads. Not only in shape (for example, countersunk screws), they differ. Also by which means they can be opened or closed. Typical are either Phillips or simple slotted screws.

Turn on a screw - the screw can not always be loosened

The screwdriver should always be of excellent quality (hardened at the tip) and fit exactly in the slot. There are also Allen key, torx and many other shapes). For unraveling, pressure must be exerted on the screw at the same time, in particular with screws with coarse thread, while it is being turned up.

Good screwdrivers are therefore equipped with a hexagon handle. Here simply the matching ring or open-end wrench is put on. Then you can press hard on the screw and still turn lever with little additional effort.

Loosen the screw head by targeted hammer blows

If a screw does not turn up or is very difficult to open, because it is rusted, for example, there are various tricks for loosening. Put the screwdriver straight on and hit the handle end several times. Often the screw loosens and can be unscrewed. Metric nuts or bolts have the same effect when you place a nut on the ratchet box and hit it.

Rust remover for unscrewing screws

Otherwise, it may be helpful to spray metal-tapped screws (tapping screws such as metric screws) the day before with rust remover. You can also heat metric screws or nuts in particular. Then the nuts or screws can be loosened well. Bear in mind, however, that you may sinter the metal, making it hard and porous.

Loosen screws by heating

Heat-opened screws should not always be reused. In particular, when the requirements for the screw connection are high. In addition, there are certain screws that can be used only once anyway, because the shaft twisted when tightening in itself. Many cylinder head bolts on vehicles are designed this way.

Tips & Tricks

If you can not remember how to unscrew a screw, you can build a donkey bridge: "L as left" means release, "R as right" means pure or twist.

Video Board: Turnin' On The Screw by Queens Of The Stone Age