NUTS, BOLTS AND WASHERS

Discover the benefits of compression washers, different threads, how bolts are graded and how to use lockwire with our beginner's guide to fastenings.

There’s a certain level of assumed knowledge when it comes to fitting the right nut, bolt and washer, so people are often reluctant to ask the obvious questions, such as what does 8.8 mean on the top of the head of a bolt, or can I replace all my rusty bolts with stainless steel ones? The answers to such questions and more are covered over the following pages with our guide to fitting the correct type of fastenings, ensuring they don’t slacken and understanding the different types of finishes that are available.

One of the biggest problems concerning classic cars and their fastenings is deciding whether they are metric, unified (UNF and UNC) or imperial (such as Whitworth and BSF). Confusingly, some bolts are a mixture of more than one type, as we shall see shortly! To add further confusion, most owners refer to UNF and UNC fastenings as imperial, but to engineers and specialist suppliers, imperial ( Whitworth, BSF, BA etc ) and unified (UNF and UNC) are two different things.

All of these different threads and sizes of heads can restrict where you buy your supplies, what tools you need and whether you can convert to another type. Ideally though, you won't use for example a metric nut and bolt on a car that generally uses unified because that can make finding the right spanner during later work something of a lottery – a near fit is rarely near enough! Hopefully our guide will shed some light on what can be a very confusing matter.