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. According to EN1993-1-8 Table 3.4 the shear strength of the bolt may be based on the tensile stress area. Minimum end distance, edge distance, and spacing for bolt fasteners according to EN1993-1-8 Table 3.3 (rounded up to nearest mm) For high-strength fastening with a professional finish, M14 fully threaded bolts do the job. Our DIN 933 M14 hex sets in A2 stainless steel and bright zinc plated (BZP) steel are ideal for a range of applications, including construction, repairs, and maintenance. M14 hex sets have a thread diameter of 14mm and a head diameter of 22mm. The thread pitch is 2mm. 14mm Hex Set Screws (Fully Threaded Bolts) The tensile stress area A s corresponds to the reduced cross-sectional area inside the threaded part of the bolt.

The interaction between shear and tension is expressed in EN1993-1-8 Table 3.4 according to the following linear relation: The width of the hexagon nuts across flats s is specified in ISO 898-2 Table A.1 for bolt sizes M5 to M39. According to EN1993-1-8 Table 3.4 the bearing resistance F b,Rd for bolts in holes other than normal should be multiplied by the following reduction factors: Oversized holes = 0.8, slotted holes with longitudinal axis perpendicular to the load transfer direction = 0.6.According to EN1993-1-8 § 3.6.1(4) the design shear resistance F v,Rd should only be used where the bolts are used in holes with nominal clearances not exceeding those for normal holes as specified in EN 1090-2 'Requirements for the execution of steel structures'. For standard coarse pitch thread and fine pitch thread bolts the nominal stress area A s is provided in ISO 898-1 Tables 4 to 7. For preloaded bolted connections which are slip-resistant at the Serviceability Limit State or the Ultimate Limit State the corresponding shear load F v,Ed should not exceed the design slip resistance as specified in EN1993-1-8 §3.9 and Table 3.2. Only bolt assemblies of classes 8.8 and 10.9 may be used as preloaded bolts. The resulting hole diameter d 0 for each type of hole (normal, oversize, short slotted, long slotted) is determined by adding the nominal clearance given in EN 1090-2 Table 11 to the nominal diameter d of the bolt. In general the stress area of fine pitch thread bolts passing through the threaded part is larger as compared to the coarse pitch thread bolts.

A is the appropriate area for shear resistance. When the shear plane passes through the threaded part of the bolt A is equal to the tensile stress area of the bolt A s. When the shear plane passes through the unthreaded part of the bolt A is equal to the gross cross-sectional area of the bolt A g.

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The first number of the bolt class corresponds to the ultimate strength e.g. 400 MPa for classes 4.x, 500 MPa for classes 5.x, 600 MPa for classes 6.x, 800 MPa for classes 8.x, and 1000 MPa for classes 10.x. For bolts with cut threads where the threads do not comply with EN 1090 the relevant resistances should be multiplied by a factor of 0.85 according to EN1993-1-8 § 3.6.1(3). where e 1 is the distance between the center of the end bolt and the end of the plate measured parallel to the load direction, p 1 is the distance between the centers of neighboring bolts measured parallel to the load direction, and d 0 is the diameter of the bolt hole.

The design resistance of a group of fasteners may be taken as the sum of the design bearing resistances F b,Rd of the individual fasteners provided that the shear resistance F v,Rd of each individual fastener is greater than or equal to the design bearing resistance F b,Rd. Otherwise the design resistance of a group of fasteners should be taken as the number of fasteners multiplied by the smallest design resistance of any of the individual fasteners as specified in EN1993-1-8 § 3.7(1). For this case elastic linear distribution of internal forces should be used as specified in EN1993-1-8 §3.12. Coarse threads are those with larger pitch (fewer threads per axial distance), and fine threads are those with smaller pitch (more threads per axial distance). Coarse threads have a larger threadform relative to screw diameter, whereas fine threads have a smaller threadform relative to screw diameter. The tensile stress area depends on the thread and it can be calculated according to ISO 898-1 Section 9.1.6.1. Minimum and maximum spacing p 1, p 2 and edge distances e 1, e 2 for bolts are given in EN1993-1-8 Table 3.3. The minimum values are: e 1≥ 1.2 d 0, e 2≥ 1.2 d 0, p 1≥ 2.2 d 0, p 2≥ 2.4 d 0, where d 0 is the diameter of the hole, e 1, p 1 are measured parallel to the load transfer direction and e 2, p 2 are measured perpendicular to the load transfer direction.

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M2 is the partial safety factor for the resistance of bolts in accordance with EN1993-1-8 §2.2(2) Table 2.1 and the National Annex. The recommended value in EN1993-1-8 is γ M2 = 1.25.

Pitch is the distance from the crest of one thread to the next or the distance from one thread groove to the next, measured from crest to crest. Pitch is also described as the number of threads per inch. The nominal gross area A g corresponds to the cross-sectional area of the unthreaded part of the bolt:

Bearing strength of bolts

By approximately ignoring the corner rounding for a perfect hexagon the relation of the distance across points s' and the distance across flats s is s' = s / cos(30°) = 1.1547⋅ s. The smallest or largest pitch diameter that fits onto a screw or into a nut, including all of the form deviations such as lead, thread angle, taper, and roundness. Functional diameter is a measure of the ability to assemble the thread. The diameter equal to the external diameter of the threads or the overall diameter of the part. (Nominal diameter is more of a label than a size. For example, a bolt and nut may be described as being ½” diameter. But neither the external threads of the bolt nor the internal threads of the nut are exactly .500 in diameter. In fact, the bolt diameter is a little smaller and the nut diameter a little larger. But it is easier to specify the components by a single size designation since the bolt and nut are mating components.)