Metric Threads are measured in Millimetres (mm) units and were developed to simplify the imperial systems. Europe moved to this system but the Americans choose Imperial as their default. A coarse thread has less helical coils per mm and a fine one has more. Coarse is used for heavier loads and fine is used for lighter loads prone to vibrations. For typical coarse pitch thread bolts the standard sizes are: M3, M3.5, M4, M5, M6, M7, M8, M10, M12, M14, M16, M18, M20, M22, M24, M27, M30, M33, M36, M39. As noted, the specification of metric bolts includes the definition of thread pitch, but if this is omitted then a coarse pitch is assumed. Metric fasteners are available with either coarse or fine thread pitches with some metric bolt sizes offering extra fine thread pitch options. It is worth noting that metric bolts with a coarse thread pitch have more threads per inch (they are more closely spaced) than comparable imperial bolts. List of common metric bolt sizes. Metric Coarse The number 1.0 is the thread pitch of the bolt, which is the distance between threads, in millimeters.

Minimum end distance, edge distance, and spacing for bolt fasteners according to EN1993-1-8 Table 3.3 (rounded up to nearest mm) According to EN1993-1-8 Table 3.4 the bearing resistance F b,Rd of the bolt is not affected by the spacing p 1, p 2 and edge distances e 1, e 2 provided that the following limits are observed: e 1≥ 3.0 d 0, e 2≥ 1.5 d 0, p 1≥ 3.75 d 0, p 2≥ 3.0 d 0. d m is the mean of the across points and across flats dimensions of the bolt head or the nut, whichever is smaller. Hex bolts from ITA Fasteners are mostly used in repair and construction work. As the name implies, they have a hexagonal head and come with machine threads for a firm and rough handling. They come in a wide range of different hex bolt sizes for custom applications depending on its dimensional requirements. These Hex Bolts come in the anti-corrosion stainless steel, alloy steel and carbon steel materials which ensures that the structure doesn’t weaken because of rust. Depending on the length of the bolt, it can come with standard threading or full threading.Albania, Andorra, Belarus, Bosnia and Herzegonia, Ceuta, Faroe Island, Gibraltar, Greenland, Guernsey. Iceland, Jersey, Kosovo, Liechenstein, Macedonia, Moldova, Montenegro, Norway, Russia, San Marino, Serbia, Switzerland, Turkey, Ukraine

The standarized properties of metric bolts are specified in the international standard ISO 898-1:2009 'Mechanical properties of fasteners made of carbon steel and alloy steel - Part 1: Bolts, screws and studs with specified property classes - Coarse thread and fine pitch thread'.

The defined diameter of metric bolts is actually slightly larger than the actual diameter of the bolt shaft. So an M8 bolt would have a shaft diameter that’s slightly under 8mm which means that the bolt should fit through an 8mm hole. But it’s common practice to drill clearance holes that are slightly larger to allow for misalignment. The standard coarse pitch thread metric bolt sizes are: M3, M3.5, M4, M5, M6, M7, M8, M10, M12, M14, M16, M18, M20, M22, M24, M27, M30, M33, M36, M39. The following table provides examples of clearance hole sizes, standard or coarse thread pitches along with fine thread pitches and their corresponding tapping hole sizes. Metric clearance and tapping drill hole sizes. Size

The tensile stress area depends on the thread and it can be calculated according to ISO 898-1 Section 9.1.6.1. Here’s a short list of standard spanner and allen key sizes that apply to the most commonly used metric nuts and bolts. Standard metric spanner and allen key sizes. Size A set screw fastens materials together by twisting it directly through the last component, into a pre-threaded hole, pulling everything together. A shoulder bolt fastens materials by passing them through pre drilled holes in the adjoining materials and cramping them between the head at one end and a nut on the other. Additional washers are often used to spread the load further. A set screw is fully threaded from underneath the head and a bolt is partially threaded (has a part-plain shank). A bolt is used when you know the length you need and a set screw can be used as a bolt if you need more flexibility in the length. Metric nuts and bolts are commonly referenced using ‘M’ sizes, for example: M3, M8, M12. But the size of a metric fastener is more accurately specified using diameter, pitch and length dimensions, in millimeters. For nuts the size dimensions used are simply diameter and pitch. The yield strength f yb and the ultimate tensile strength f ub for bolt classes 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, and 10.9 are given in EN1993-1-8 Table 3.1.They are designated as above also including the pitch of thread in mm e.g. M8 × 1, M14 × 1.5, M27 × 2 etc.