Coach Bolts - Metric - Self Colour

Often called carriage bolts or cup square hex bolts, coach bolts have a round head with a square underside.

Coach bolts are available in a range of sizes. All have metric coarse threads. They are most commonly used in the construction and timber trades.

Metric is the most common thread type in production today. Usually specified as M then a number x another number. This signifies the thread diameter and the length of the fastener.

For example M4 x 30 means that the major thread diameter (the external distance across the outside of the thread) is 4mm and the length is 30mm. Length is usually measured from the underside of the fastener head.

Steel products described as having a self colour finish are best suited to internal applications, as they have no additional protection against corrosion. The shade of a self colour finish can vary from bright metal to black, and it will change over time with oxidisation.

If you plan to use self colour finishes outdoors you should paint them to give them a protective coating.