There are many different types of nuts and bolts, and screws available for DIY projects at the moment, and keeping track of which ones you need can be difficult. Today, we’re going to be looking at one specific type of screw: the coach screw.
Coach screws have a square or hexagonal head with an externally threaded cylindrical shaft that tapers to a point at the tip. They are usually used to keep heavy lumber together and to secure metal to timber and, in certain situations, masonry or concrete. They are sometimes known as lag screws or lag bolts, but you should note that they are not the same as coach bolts or carriage bolts.
What Are Coach Screws?
A coach screw is a ‘single-component’ fastening with a coarse single wood thread meant to be secured into timber. A coach screw is generally fastened into wood, but it may also be fixed into nylon wall plugs to provide a heavy, strong masonry fix. Coach screws do not come with nuts and do not require them since the coarse single thread is meant to fasten straight into wood.
Coach screws are available in a variety of sizes and are made to DIN 571 German national standard standards.
Coach Bolts vs. Coach Screws
Coach screws are hexagonal or square-shaped fasteners with a pointed tip. They are commonly used for wood-to-wood or wood-to-metal connections because they have a strong grip and pulling force.
Coach bolts have a threaded shank and a smooth, dome-shaped head. They are frequently employed in applications that need a more streamlined look, such as building or furniture assembly.
Using Coach Screws on Timber
To prevent wood splitting, all coach screws require a pilot hole to be drilled with a general-purpose drill bit, such as a twist drill bit, before being screwed into place. To drill the pilot hole, you’ll need a wood drill bit. They vary from metal drill bits in that they feature a tip at the end to prevent them from sliding out of position.
When utilizing softwood, the pilot hole diameter should be half the diameter of the coach screw and three-quarters when using hardwood. When installing an 8mm coach screw, for example, the pilot hole should be 4mm for softwood and 6mm for hardwood. After drilling the pilot hole, the coach screw may be pushed directly into the wood.
When fitting coach screws into wood, it is best to use a washer to prevent the screw head from being embedded in the wood on contact. This will also make removing the screw at any stage easier. A flanged coach screw is another possibility. This is a coach screw with a washer embedded into the head.
Using Coach Screws on Masonry
When using a coach screw to secure heavy things to masonry or brickwork, you must first drill a hole using an SDS drill bit. It is critical to utilize a wall plug with a coach screw to secure any large object fastened to the wall. The wall plug must be the same size and depth as the hole you drilled.
To avoid damaging the head, coach screws must be tightened or loosened using the appropriate size spanner, wrench, or impact socket. Size the head across the flat edges, not from point to point.