What are rules made of?

3rd March 2020

What are rules made of?


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		Rules are made from various materials and can be rigid or flexible. The quality of a rule will usually be reflected in the price, the reputation of the brand and the specification. The material your rule should be made of will depend on its intended uses.

		Wood
		Wood is a traditional material for making rules. The wood usually used is fairly inexpensive and reasonably durable. Wood is quite a lightweight material, so it’s easy to carry around. The markings are usually etched onto the wood, therefore, they won’t rub off like some marks that are just printed on. Etched marks are engraved into the wood and then highlighted with ink.

		Wood is often softer than metal or high-impact resistant plastic and the edges of wooden rules can be dented or damaged quite easily. If using them with cutting tools, it can be very easy to cut or chip into the wooden edge, so they are not generally suited for use with cutting tools. Thin wooden rules can be delicate and easily snap.

		Rules can get damaged if they get wet: wood can expand and change shape, making the rule inaccurate. However, if looked after properly, a wooden rule should last a long time. Some rules are made of very high quality hardwood – these rules are likely to be more accurate and durable than cheaper versions, but more expensive.

		Plastic
		Standard plastic rules are usually very inexpensive. These types are often brittle and easily damaged or broken. Some rules are made of more durable plastic, although these will be more expensive. Higher quality plastics differ: they may be hard and therefore rigid, or softer and flexible so they can be bent without deforming.

		The marks on plastic rules can be put on through various methods. The cheapest way to apply the marks to a rule is to print them. However, this means they can rub off over time. Some plastic rules have gradation marks moulded into the body when they are produced – these won’t rub off but may not be particularly accurate.

		The markings on more expensive rules will be machine etched onto the plastic. This method produces the most accurate gradations as they will be precision set to official standards. Machine etched gradations are engraved through the movement of gears.

		Plastic rules come in a variety of styles, and the material means they are easily produced in various colours. You can also get clear plastic rules, which allow you to see through them as you use them to measure or draw, but this would mean only one side could have gradations marked on it. The quality of plastic a rule is made from will usually be reflected in the price and the reputation of the brand and should be stated in the specifications.

		Metal
		Metal rules are generally the most durable type, but often the most expensive. There are a few different metals which they may be made from. Metal rules are better for use with cutting tools than wood or plastic ones as the edges are not so easily damaged. However, metal rules will often be heavier than plastic or wooden rules.

		The markings will usually be etched onto a metal rule, making them durable, as they can’t be rubbed off. Metal rules can have gradations marked on with geared machines set to precise measurements. They can also have marks photo etched onto them, sometimes called photochemical machining. Parts which are photo etched use a photoresist chemical to carve precise areas out of the metal. For high quality rules both these methods should offer high levels of accuracy.

		Carbon steel Good quality steel rules will usually be made from high-carbon steel, which has been tempered and hardened. They will often be chrome plated, for corrosion resistance, and have a satin finish, to make them easier to read. Steel rules can have the gradation marks engraved onto the rule with photo etching or precision machining.

		Stainless steel Stainless steel may be used to make rules as this is naturally corrosion resistant, without needing a coating. These rules are often fairly inexpensive, but they can’t be hardened as much as carbon steel. This means some stainless steel rules can be easily deformed; if they are bent too much they may retain a curve. More expensive stainless steel can be hardened, nearly as much as carbon steel.

		Aluminium Aluminium rules are more lightweight than steel rules and are very resistant to corrosion. Steel is much stronger than aluminium, which may be easy to deform. These rules are usually cheaper than steel rules.

		Which material?
		Factors which should influence your choice of rule material will usually be: how rigid the rule needs to be, how light the rule needs to be, the accuracy needed for measuring, what it will be used to do, and how often it will be used.

		Steel rules will usually be the most expensive, but they should be the most durable, accurate and rigid. However, they will also be the heaviest. Aluminium rules are lightweight and resistant to corrosion. They will not be as strong as steel rules but will be cheaper. You can also get some wooden or plastic rules with metal edges or ends – this should protect the softer material.

		Wooden rules will last a long time if they are cared for. They are light and fairly inexpensive, but they can easily be damaged. Plastic rules are the most diverse. Cheap plastic rules are likely to be slightly inaccurate and easily damaged. More expensive plastic rules should be accurate, lightweight and durable. Plastic is waterproof and corrosion resistant, but may not be suited to use with a cutting tool.