What are Bolts

This page is for information and answers to common questions asked relating to bolt fixings.

What is the difference between a bolt and a set?

Bolts have a portion of plain shank and a set is a fully threaded bolt.

The best scenario is to have a shank where possible as the shank has additional strength and will not cause abrasion if the component vibrates or moves. Therefore, hex sets have the advantage of being versatile where the length can be longer without the worry of the shank being longer than the fitted part.

What grade are hexagon bolts?

Hexagon bolt fixings and sets come in various grade. Generaly the higher the grade the greater performance and superior strength.

Examples of Common Grades

Grade 4.6 and 4.8 – Mild steel – Not as common now in Hexagon head but commonly used in coach bolts, machine screws, roofing bolts, gutter bolts etc

Grade 8.8 – High tensile – The most common grade of hexagon head fasteners due to the high strength. Main uses include steel fabrication, timber construction, Engineering etc

Grade 10.9 – High Tensile – Hex head often used in the manufacture of vehicles such as cars and trucks due to the higher breaking strains. Countersunk socket head bolts are mainly manufactured in grade 10.9.

Grade 12.9 – High Tensile – Available in hexagon head and socket cap head – Often used in engineering and vehicle components.

Grade 14.9 – High Tensile – Mainly use in safety critical components.

Grade B7 – High Tensile – A fastener made of chromium-molybdenum alloy steel for use in high temperature applications such as the petrochemical industries.

Grade S & 5 – High Tensile – The grade for Imperial high strength bolts in UNC (unified coarse) and UNF (Unified fine).

Grade R – High Tensile – Older style thread types defined as high tensile such as BSF (British Standard Fine) and BSW (British Standard Whitworth).






What are the bolt standards?

Din 933 / ISO 4017 – Full Thread Hex Head

Din 931 / ISO 4014 – Part Thread Hex Head

BS1768 – Standard for Imperial threads UNF and UNC bolts and sets.

What is zinc plating?

Zinc plating is primarily used to protect metals from corrosion effects. This coating prevent corrosion of protected metal by forming a physical barrier and acting as a sacrificial anode. Even when this barrier is damaged. When Zinc and iron/steel are joined and placed in an electrolyte; a cell is formed, in which the zinc becomes the anode and the steel the cathode. Subsequently, zinc is sacrificed, and the steel does not rust.

Once exposed to the atmosphere, zinc reacts with oxygen, forming zinc oxide, which further reacts with water molecules in the air to form zinc hydroxide. In turn, zinc hydroxide reacts in the atmosphere with carbon dioxide to yield a thin, impermeable, tenacious and quite insoluble dull gray layer of zinc carbonate. Which adheres to the underlying zinc, further protecting it from corrosion.

The number of methods used to apply zinc coatings, each determines the coating’s thickness and ultimate durability in specific environments. The most commonly encountered types of zinc coatings are as follows:

What is a Zinc Plating? – Definition from Corrosionpedia

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