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NORMAL WEAR AND TEAR
Published by PPM Locksmiths Cardiff in Locks and keys • 31/10/2011 22:47:47

NORMAL WEAR AND TEAR

The Colorado River flows south from the Rocky Mountains of Wyoming to the Gulf of California in Mexico. Where it runs through the state of Arizona, it has eroded the underlying rock over a length of 277 miles to form the natural wonder known as the Grand Canyon. Over the past 17 million years the river has followed the same course to the sea, cutting a deep channel up to a mile in depth, and 18 miles wide in places, and exposing as much as 2 billion years of earth’s geological past after wearing through layer upon layer of solid rock.

A great mass of the upper levels of relatively soft sedimentary rock has been pushed upwards in the Grand Canyon by geological action. Yet the erosive action of mountain water has worn through these rocks to the harder igneous and metamorphic bedrocks, such as granites, schists and gneisses, that lie underneath, and the river continues to cut its ceaseless path through ever deeper levels. It is one of the world’s most stunning examples of wear and tear.

Years ago, an old pub quiz favourite was “What is the hardest natural substance on Earth?”, and the answer, as many people know, is diamond. Diamonds are formed when chunks of pure carbon are compressed under enormous pressure and high temperatures so that individual atoms are realigned, and re-organised to form an incredibly tough structure. In other words, if you get a lump of coal the size of a grapefruit, and set a mountain on top of it, you will end up with diamond the size of an orange. If you subject it to millions of tons of even pressure at a certain temperature, the resulting diamond will be clear and flawless.

In 1812, the German mineralogist Friedrich Mohs devised a scale of mineral hardness. On the Mohs Scale diamond was rated 10, and talc, the softest mineral, rated just 1, with all the other minerals ranked somewhere in between. Although hardly used nowadays, it is useful as a comparative guide for metals. Iron has been used by humans for about 5000 years. It is abundant and, in its purest form, is malleable and easily worked. It rates about 4 on the hardness scale, but if you heat it to a white hot liquid, and add about 2% carbon, you create steel, which can have a hardness of between 5 and 8.5, and can therefore be as much as 1000 times harder than iron on its own. In effect, adding the ‘diamond factor’ to iron creates steel. But this can be taken even further.

We can make steel tougher and lighter by adding titanium, at 6 on the scale. With some chromium, at about 9 on the scale, we create ‘stainless’ steel - an alloy of iron, carbon and chromium, which is very hard-wearing and durable. Or by re-heating the steel, and adding further carbon, we can produce case-hardened and through-hardened steel, which may also benefit from the addition of boron, at about 9.5 on the scale.

The art of sword making, brought to near perfection by supremely skilled craftsmen 500 years ago in Japan, and independently by the smiths of Toledo in Spain, involved continually re-heating the sword, hammering the metal as it cooled to force molecules to realign. This process would be repeated many times, until the sword had amazing strength and flexibility. It would then be capable of ‘taking an edge’ - sharpening to an incredible degree. Metallurgical techniques for improving structures at a molecular level, while not understood by medieval artisans, have been known for centuries, and similar techniques are still used in modern engineering.

When steel is used to make moving parts for any mechanism, there are certain problems that have to be overcome. First, you have to make tools that are harder than the base material to fashion the shapes. Once formed, you have to deal with friction and corrosion in the finished item. In a small scale mechanism like a lock, untreated steel wears away relatively quickly. In a large machine, bearings and lubricants reduce friction, but bearings in a lock would make it heavy and cumbersome. So, alternatives to hardened steel are routinely used in high quality domestic locks and for keys.

The lockmakers of the past commonly used brass to make the working parts for locks. Although relatively soft as a metal, brass doesn’t corrode much, and because it can be easily machined, and polished to a very smooth surface, friction is minimised. Because of these properties, and relative cheapness and abundance, brass components are still used in some security locks. Chubb mortice locks, for example, always employed brass levers and detainers, along with brass keys to operate them, reducing wear and extending the working life of the mechanism.

It is not unusual to see original Chubb keys that are decades old, but the same block of brass would be used to make the lock parts and the keys to operate them. If you use steel keys for a Chubb lock, however, it will shorten the working life of the lock, as the brass levers are rapidly worn away by the harsher steel, so at PPM Locksmiths we always use brass keys for Chubb locks. In some locks that use hard steel levers and softer alloy keys, it’s the keys that wear very rapidly, and cause problems with the operation of the lock. The trick, of course, is to use metals of a similar hardness for the internal workings of a lock and for the keys. This is the principle of ‘matched metals’. The greater the difference between the Mohs rating for the lock components, and the rating for the keys, the more likely that problems will arise. If you use hardened steel components for the lock, you would have to have hardened steel keys to go with them, and employ diamond cutters to copy them, making them expensive and impractical.

Many budget locks now available use neither steel or brass for either internal levers or keys. It costs more money to keep metals pure and unadulterated, and it costs more to engineer harder metals. In recent years the price of scrap metals has leapt up, and so it is cheaper for a manufacturer to use raw materials that are a mixture - a bit of brass, some steel, mixed with tin, aluminium, zinc, iron - all sorts. When you mix metals in this fashion, you get huge variations in the quality of the finished product, but you keep manufacturing costs to a minimum.

When you mix a variety of different molten metals together, they have different melting points. At any given temperature, some metals will be more fluid than others, and so they won’t really mix properly and evenly unless it is a very high temperature. Some of the metals will form lumps within the mix, like knots in a tree, or like dumplings in a stew. When you pour the molten mixture into a mould, the knotty lumps will cause weaknesses in the overall structure of the casting. As they cool, metals with a higher melting point will form solids when other metals are still liquid. Cooling can cause micro-fractures and flaws in the integrity of the casting, which will probably break under stress - not very good if you use it in a lock which is supposed to withstand a force attack.

To most customers, there is no appreciable difference between the cheap lock at the DIY store and the more expensive lock from locksmiths - except the price - but the crucial differences are being concealed. Manufacturers can be blamed for this when they produce ‘budget’ locks for the DIY market, packaged with a household name, but lacking the quality standards that made them well known in the first place. Also, budget locks made by new manufacturers lacking design expertise are often makeshift affairs. The customer is a guinea pig conducting field tests on an untried product. These locks may fail very rapidly, and if they lock you out of your own home, you will have to call a locksmith to open the door. Trying to save money costs more in the longer term.

In a good quality lock, the materials that are used for keys and the moving parts of the mechanism are of a similar hardness, so that every part wears equally throughout the lifetime of the lock - the principle of ‘matched metals‘. The easiest way to upset this is to introduce new keys that are of a different hardness, or that aren’t cut correctly, so they scrape internal components, shaving the metal away rather than smoothly moving against it. A poorly cut key can very easily halve the potential lifetime of a decent lock. So imagine what it does to a cheaply manufactured lock.

With locks of any type, as with any metal mechanism employing moving parts, a spot of lubrication will significantly extend the lifetime of the lock. However, we urge you to avoid viscous lubricants such as oil or grease. Anything sticky will cause greater problems to a faltering lock. The keyhole is often an effective means of ventilating an enclosed area, and a significant amount of dusty air will pass through a keyhole on a daily basis. This means that the lock components, where it is sticky, will gather particles from the air which will interfere with its operation. On numerous occasions, a dirty ball of fluff has stopped a perfectly good key from turning the lock. When this happens, the lock has to be opened up and cleaned thoroughly, before it causes a lockout.

To keep any lock operating at optimum levels, flush it out now and again with WD40 or GT85 - non-viscous lubricant sprays that soften the rubbing motion of bare metals against each other. Metal surfaces should be smooth rather than jagged, so make sure your new keys are properly finished by the keycutter before you try them in the lock. Finally, if your lock is snagging, and the keys are becoming difficult to turn, either call PPM Locksmiths to advise you, or bring the lock in to our Cardiff city centre shop for a quick assessment. In most cases, if the warning signs are heeded, swift action will prevent a more serious lockout.

With care and occasional attention, a good quality lock can last for 30 or 40 years, and some will last even longer than that. It is not uncommon to see safe locks that are more than a hundred years old and, after reconditioning, there is no reason why they can’t go on for another century. Year after year, and pound for pound, a good quality lock represents much better value for money than a cheap lock that will be worn out after just a few years.

Every lock gives up eventually, and just as the continual flow of the Colorado River has worn a deep channel in the Earth that can be seen from space, so metal upon metal takes its toll. Every new product we are offered is examined and tested to ensure it meets our exacting standards. At PPM Locksmiths we are more than happy to offer products with lasting quality at an affordable price.


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PPM Locksmiths Ltd 7 Dominions Arcade Queen Street Cardiff - Phone 029-20231717