Help & Advice

 How to measure the sizes of standard bolts and screws

Diameter (metric): Measure the distance to the outside edges of the thread and round up to one decimal place.

Diameter (inch): Measure the distance to the outside edges of the thread and round up to the nearest 1/32".

Length (metric): For all head styles except countersunk measure the distance from uder the head to the end and round up to the nearest millemeter. For countersunk style head measure the overall length from the top of the head to the end and round up to the nearest millimeter.

Length (inch): For all head styles except countersunk measure the distance from uder the head to the end and round up to the nearest 1/16". For countersunk style head measure the overall length from the top of the head to the end and round up to the nearest 1/16".

Disadvantages of using stainless steel fasteners

Tensile strength is less than high tensile.

Galling effect can jam the thread when tightening. For more information click here

Usually more expensive than zinc plated high tensile.

Why bolts on modern vehicles are different to commercial 'industrial' bolts

The bolts on modern vehicles have been specified and designed for optimum strength and purpose and can be manufactured at economic rates for quantities on large production runs.

On larger sizes the heads are usually smaller for lightness and incorporate a flange for neatness and faster assembly.

Thread lengths vary and the lengths can be very precise for an exact fit.

For safety specific items such as seat belt, brake, steering, engine and transmission the vehicle manufacturer's part has been designed to be more than adequate and anything else could compromise safety and we do not recommend the use of commercial items for these purposes.

Industrial bolts are manufactured to a set standard of dimensions with reasonable tolerances but are more versatile and cheaper.