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. 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. Masonry Also known as lag screws or lag bolts, they are heavy-duty screws that are designed for metal to timber connections, or to join heavy timbers. How do you choose the right coach screws for your application? And how do you select the right coach screw sizes?

Stainless steel – offers high corrosion resistance making them ideal for outdoor use. They are also highly recommended for use with timber such as oak and cedar as these particular types of wood can contain acid and chemicals which can corrode metal. There are two main stainless steel grades: 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. 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. Passivated (or zinc plated) coach screws are electroplated using a zinc coating. Many of our passivated products are then finished in yellow chromate. Passivation offers increased corrosion resistance, although for maximum corrosion resistance use a galvanised screw. Unlike the galvanised option, however, passivated screws typically have a high-shine finish. These are ideal for applications where aesthetics are important. Browse our range and you’ll typically see three types available: passivated, galvanised and stainless steel.Passivated – 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 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 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.

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.

TurboSilver Woodscrews

To avoid splitting timbers, drill a pilot hole before inserting any screw. Pilot holes should be half the diameter of the screw when using softwoods, and three-quarters its diameter when working with hardwoods. Our range or coach screws varies from screw diameters, lengths, head types and finishes. Browse from our range of zinc and yellow passivated or exterior coated green finish types to find the right product for you needs. Lag screws have two measurements. The M rating is the diameter of the screw thread; the measure in mm is the length of the screw from screw tip to the underside of the hexagonal head.