Many imperial threads sizes that are now antiquated caused by changes in demand patterns from countries such as the USA who now drifting towards metric products. This increasing globalization of metric threaded fasteners does not necessarily mean that all variations are commonly available. The team at Challenge (Europe) Ltd are well use to this situation and carry extensive stocks of standard sizes of industrial screws plus a wide experience in supply of non-standard sizes, threads, lengths and materials. Kevin Moorcroft explained,
“We find that standard sizes of metric products have grown extensively. ISO standards now cover a whole range of products complimentary to old imperial sizes, as well as expanding on the original ranges of metric fasteners, e.g. metric socket head cap screws bearing once only available in 12.9 grade are now offered under the ISO standard in 8.8, 10.9 and 12.9 grades to suit a wider range of applications with varying requirements of tensile strength.”
However, head configuration can have an effect on the size of metric fastener that can be used. For example, if you use a M6 bolt fastener with a hex head but find conventional spanner access limited, you could then use the recessed drives such as a hexagon (socket) or multiple splined variants. Another substitute is to go to a smaller diameter with an upgrade in material specification, although this may lack a greater deal of examination in order to avoid non-preferred diameters such as M7, M9, etc.