So, for example, a screw with the dimensions M8 x 100mm is 8mm in diameter at the thread’s maximum width and 100mm in length from the screw tip to the base of the screw head. The screw head itself remains proud of the drill hole. How do you choose the right coach screws for your application? And how do you select the right coach screw sizes?

A4(316) - can handle high and low temperatures but has a higher corrosion resistance making them ideal for coastal areas or areas with high pollution Browse our range and you’ll typically see three types available: passivated, galvanised and stainless steel. It is advisable to drill a pilot hole in the timber before fixing as this will reduce the chances of splitting the timber, particularly when working close to the edge. When using coach screws on timber, it is advisable to add a washer to avoid embedding the screw head into the wood on impact. This will also make it easier to remove the screw at any point. Another option is a flanged coach screw. This is a coach screw with an integrated washer built into the head. MasonryPassivated – this is a two-part deep cleansing process to remove free iron or other contaminants from the surface. This process maximises stainless steel corrosion resistance Washers can be used with the coach screws to give a flat surface for the bolt to fix against and also to reduce the chance of the timber splitting as the screws is tightened. At Fastco we have repair washers ranging in sizes between 20mm and 50mm in diameter.

Bright zinc plated – provides moderate corrosion resistance and is suitable for indoor use in a dry environment

Galvanised coach screws are zinc-coated, low-cost steel screws. Typically a matt finish, these screws are often used in automotive parts, sheet metals, industrial applications and construction. The zinc coating offers corrosion resistance. This makes galvanised coach screws suitable for outdoor, hot, wet and humid environments. Stainless steel coach screw types are great for outdoor use. Because there’s no coating, the corrosion resistance comes from the screw’s composition. Stainless steel coach screws are our most durable type and are also resistant to the oils and acids in many timbers. All coach screws require a pilot hole, using a general-purpose drill bit such as a twist drill bit, before they are screwed into place, preventing wood splitting. You will need a wood drill bit to drill the pilot hole. They are slightly different from metal drill bits as they have a point at the end to stop them from slipping out of position.