Will it be a hex head, a coach bolt or a threaded rod? If you’re trying to buy nuts and bolts for your application, you may need a little help deciphering what’s available. Here’s the Tradefix Direct guide to bolts, nuts and washers.
When should I use coach bolts?
You’ll find coach bolts are the fixing of choice for most large building projects. They are typically used at critical points within a structure to join timber segments together and are far more durable option than nails, screws and many other bolt types.
Roofing bolts have lots of other applications beyond roofs, but they are particularly handy for metal to metal roofing jobs where the broad, flat head creates a more secure fix. They’re also ideal for trunking and cable trays.
The j-shaped hook bolts sit over the edge of metal beams (purlins) and prevent the bolt from moving whilst being tightened – important not only for creating a water-tight seal, but also for making fiddly work easier.
Hex bolts are appropriate for fixing wood, steel and other construction materials. With a high tensile strength they are a good ‘go to’ option for all applications requiring a strong fixing. Their size and head shape also makes them easy to fit using the widest possible range of tools – ideal for tight spaces.
Threaded rods don’t have a head – they’re simply all thread in a rod which you cut to length. That makes them extremely versatile and ideal for a wide range of hanging, connecting or fixing applications. For most durable results, fix in place using a chemical resin.
Eye bolts (aka lifting eyes or eyelets) are bolts with a loop at one end. They are designed for lifting loads (such as ropes, cables or suspended lighting) and the load they can carry is determined not only by their size, but also by their construction. A simple folded eye bolt, for example, will carry a much lower load than a forged eye bolt. Hook bolts perform a similar function. Again, look for forged bolts to ensure the load doesn’t cause the hook to open.
You can still buy cheap bolts and nuts without sacrificing performance. Take our high tensile bolts (aka set screws). Tensile strength is simply a measure of the load a bolt can support without fracturing. So just how high a load can high tensile bolts take? Our bolts are grade 8.8 (you might see them marked with an S or three radial lines – all of which mean the same thing). This means they are heavy duty bolts capable of withstanding a stress of 45 to 49.9 metric tonnes per 6.45 cm². They’re well suited to a variety of tasks.
As the name implies, holding down bolts (or HD bolts) are anchoring bolts typically used in fastening column base plates. Their structural role requires high tensile strength, which is why ours are Grade 8.8.
There’s a surprising range of options when it comes to nuts, from wing nuts (handy if the nut’s being removed with any regularity) to Nyloc nuts with a nylon insert that prevents the nut from loosening over time.
Not always, but washers can be essential if you’re bolting through wood or other relatively soft materials. When you tighten a nut and bolt assembly the head of the bolt and the nut can both bite into the surface material. That doesn’t just look bad – it can also cause damage. A washer helps distribute the load of the fastener across a wider surface area, reducing the risk of damage. The larger the washer, the greater the effect, but there may be a trade-off in terms of aesthetics. Penny washers perform whilst keeping a low profile. Square plates offer even greater load distribution but are a little more obtrusive. They’re ideal for use with coach bolts.