How does a spanner work?

2 min

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A spanner functions by gripping hold of a fastener and then twisting it – either in a clockwise or anti-clockwise direction – in order to loosen or tighten it as required. The size and shape of the head – known as its profile – either fits around, into or over the fastener.

After the head has been turned friction between the fastener and the profile at the points of contact result in the spanner mechanically gripping the fastener and providing a turning force known as torque that causes it to turn. 

The shaft has to be turned onto the same exact plane as the fastener in order for the tool to be turned. This can be achieved by the user gripping hold of the shaft and then either pushing or pulling it. The shaft functions in the same manner as a lever, with the user able to magnify the force input and making it easy to turn the fastener. 

What is the purpose of a spanner?

A spanner provides mechanical advantage and grip in the application of torque so as to turn objects such as the likes of rotary fasteners (nuts and bolts etc) or to stop them from turning. Spanner is the standard term for this in the majority of Commonwealth nations, save Canada. 

Many people wonder if a spanner is the same thing as a wrench, but a spanner is actually a wrench that can be adjusted. It is a form of wrench that comes with an opening and in some cases with small teeth. This is so that it can clasp over the bolt or nut and ensure a solid grip. 

How are spanners made?

The drop forging process is used to manufacture the majority of spanners. This process involves steel rods being cut into short lengths that are referred to as billets, with each one passing through an induction heating coil that makes use of electromagnetism in order to ensure the metal is heated to about 1000 degrees Celsius. The spanners can then be tempered so as to increase the strength of the steel. 

What does a spanner look like?

There are a number of different types of spanners, all of which come with a distinct hook shape. Some spanners can also be multi-tools that make use of double-sided hooks. The C spanner is the most common type of spanner, which has an open head that resembles the letter C, hence the name. The jaws of the C spanner are intended to correspond to the nut that is of a similar size. 

An obstruction spanner meanwhile is similar but has more steeply angled jaws that are better suited to get to nuts that are situated in tight places, while the ring spanner comes with a completely enclosed ring that is a precision fit over a square or hexagon bolt. Correctly placing the ring spanner can take time, but it offers a much stronger leverage than is the case with open spanners. 

It is important to make sure that your spanner is the right size and properly sitting over the nut before you twist it to avoid it slipping and causing injury or damage. 

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