The most important function of a washer is to distribute force concentrating on one single point at the screw binding. Without washer, the torque would concentrate on a small surface of the screw and would therefore damage the spare part. The washer spreads this force on a larger surface – kind of it, isn’t it? This effect can be best perceived if we put a screw in wood or in a thin plate. Basically, the screw crashes the material. It is the same as if you were walking in snow to the knee, but if you increased the surface with a pair of skis, you would sink less because the skis spread the load on a surface significantly larger than your soles. Another relevant function of the washer is to protect the surface of the object you are working on. The screw does not rotate on the surface of the object, damaging it, but instead, it rotates on the washer. We use "washers" in other areas of life as well. For example, we put pallets under products, carpets under the chair, soles under our feet, coasters under the teacup: all of these have their washer effect. It goes without saying that surface size, material quality and thickness are all relevant features. It is just the same with washers. Let’s see what options we have!
Categorization based on quality and quality material
- toughened steel
- anti-corrosion steel (A2)
- acid-resistant steel (A4)
- yellow copper
- chemically resistant plastic (PA)
- DIN 125 flat washer for general screw bindings
- DIN 440
- DIN 9021
- DIN 436 For wood, we use a broad, wood-bound washer. Wood-bound washers exist in round and square (DIN 436) design, but it is more of an aesthetical question. The versions mostly differ in their internal-external diameter and thickness proportions. We asked a user working in wood industry why he prefers this or that type. He answered that he uses the one it is easier to get a drill for. When it comes to design, fix size proportions facilitate the work, for instance, the external diameter size of a DIN 9021 is the threefold of the drill diameter – easy to count with.
DIN 434 - DIN 435 washers for U and I beams. These washers follow the obliquity of profile section surface. The U washer compensates this difference in thickness by 8% , the I washer by 14%. Thanks to the washer, the screw can be bended perpendicularly and lies on the U or I profile with its complete surface size. The drill diameter of these washers is bigger than of any other washers, and for a good reason: a drill hole larger than the screw thread diameter lets any screw coming from a non-perpendicular angle pass through easily. If the drill hole was narrow, the obliquely coming screw would be very likely to get stuck.
For sheet envelopes and corrugated sheets we recommend sealing washers, which are combinations of a slightly cone-shaped metal plate and an internally volcanized elastomer (e.g., Neopren or EPDM). During installation, the screw head presses down the cone and the volcanized rubber comes out and enters the screw thread (from thread direction), and the edges of the washer are pressed on the surface of the object, thereby sealing the installation point.
In Electronics contact and insulating washers are used. Contact washers increase whereas insulating washers zero out the transition of binding point. There exist insulating washers which is composed not only of a disk, but also of an insulating material that embraces the thread and the head. These washer cannot be lost as threads are calendered on the screw additionally. This increases diameter, and the washer cannot therefore fall out through the thread. You can choose between flat, spiral, toothed and wavy screws or the combination of these: what is important is that everything is where it needs to be, saving us a lot of time and work in production! Heavy machines, sports motors, martial arts, football and all the other boyish stuff – women keep up with us in everything nowadays, why would it be different with screws? If there is a washer that practically cannot get lost, why wouldn’t we have a washer-nut combination? We do have it, under the name combined nut (item number: 9085). With this combination, the washer is flanged in a way that it rotates easily but cannot fall out – it is really practical.