variant of rods with a fine thread, i.e. with a slower rise, thanks to which it is possible to achieve a better tightening force and a higher resistance to vibrations, for example. The basic and most widespread class in the market in a refined state, it is used wherever lower classes of strength are no longer sufficient. Suitable for joints subjected to high loads, often recommended for friction joints with controlled tightening. With its strength, it can easily replace lower classes when using a smaller size. Guarantee of notch toughness min. 27J at -20°C. Strength class 8.8 can be galvanized in most cases. The possibility of hot-dip galvanizing limits the chemical composition. Made of carbon or alloy steel, hardened and tempered.