This standard gives the general dimensions and tolerances of black hexagon bolts, screws and nuts with ISO metric threads in diameters from 5mm to 68mm inclusive; basic dimensions for sizes greater than M68 are also included.
This standard specifies mechanical properties of black hexagon bolts, screws and nuts made of carbon steel and alloy steel when tested at an ambient temperature range of 10°C to 35°C. Dimensional requirements are included for bolts, screws and nuts finished black all over and for those which have partially machined finishes.
NOTE1 Fasteners (the term used when bolts, screws and nuts are considered all together) that conform to the requirements of this standard are evaluated at this ambient temperature range. They might not retain the specified mechanical and physical properties at elevated temperatures and/or lower temperatures.
This standard is not applicable to fasteners used in applications outside of the range -50°C to+150°C.
NOTE2 Fasteners conforming to the requirements of this standard are used in applications ranging from -50°C to+150°C. The use of fasteners in applications outside of this range, and up to a maximum temperature of+300°C, might need to be based on the advice of an experienced fastener metallurgist for determining appropriate choices for a given application.
NOTE3 Nuts in accordance with this standard cannot be fully loaded with sufficient assurance up to the yield point of the appropriate bolt, or beyond this, without the possibility of the nut thread being stripped, and for this reason it is essential that new designs of nuts for use with BS4190 bolts and studs conforming to this standard conform to BSENISO898‑2.
NOTE4 Nuts with an effective height of less than 0.6d and/or with a width across flats or outside diameter of less than 1.4d are excluded from the mechanical requirements specified.
The dimensional requirements of this British Standard are also applicable to non-ferrous and stainless steel bolts, screws and nuts.
Information on strength grade designation system for steel bolts and screws can be found in AnnexD.
NOTE5 The term “black” does not necessarily relate to the appearance of the products, as these can be of bright appearance or black in the finished state. The term implies the comparatively wider tolerances to which these products are usually made.
NOTE6 In addition to the definitive requirements, this standard also requires the items detailed in Clause3 to be documented. For compliance with this standard, both the definitive requirements and the documented items have to be met.