CHOOSNERS THE CORRECT & WRENCHES

Never use anything but a good quality spanner of the correct size to turn a nut or bolt: if you use a gripping tool, the damage caused could render the work useless. If you want to grip work.- there are two main points to bear in mind when selecting the tool for the job: it must grip the work securely and not slip and it must not damage the work – although there may be occasions when, due to the nature of the work, it will not matter if your gripping tool marks the work surface.

Spanner sizes

Spanners are available in a range of sizes, depending on the system of the work in hand and are made with either standard or short-length shanks. Whitworth and BSF The size of the hexagons on British Standard Whitworth and British Standard Fine bolts differs for any given diameter of bolt. In practical terms this does not matter, since the same set of spanners will fit both scries of bolt and nut hexagons. This means a spanner designed to fit the hexagon head of a jin BSF bolt will also fit the hexagon head of a ^in BSW bolt: a similar relationship exists throughout the range.

The normal set of spanners will range up to 2in BSF. but there is little need for the largest sizes. A suitable range of BS spanners for use in the home workshop would be: £x^, x^, x-^, x^. and 4 x. The Imperial sizes indicated are those found marked on the jaws of the spanner and indicate the bolt diameter. Most spanner sets are arranged in such a way that the larger size on one spanner is the same as the smaller one on the next spanner up. Thus a -^ x ’m follows on from a ^ x-j^ in. which means you can use one of the -^in ends on the bolt and the other -fc in end on the nut. American and Unified series Spanners made to fit these series of nuts and bolts are identified by the distance measured across the fiats of the hexagon -and not by the bolt diameter. For example, a spanner marked -^ A/F measures JE in across its jaws and is designed to be used on a bolt with a diameter of 4in.

Metric series These spanners are also identified by the measurement across the flats of the bolt head. The most useful set would be of 9-22mm spanners. Unfortunately the ends of these spanners may not coincide with the next spanner in the set and therefore to hold both the nut and the boll at the same time you need two similar spanners. The metric series is becoming more widely used than the other series, particularly on such things as cars and appliances. Bear in mind metric spanners are not interchangeable with those of other series.

Open-ended spanner

The most common type of spanner is the open-ended version – and it is often the most abused, bearing in mind how versatile it is. A good quality open-ended spanner will operate very efficiently, with the advantages of being easy to slide onto a nut or bolt where access is limited, of needing access to only two flats of the nut or bolt in order to turn it and of being able to operate even when the spanner shaft is not quite at right-angles to the bolt axis.

The head of the spanner is set at an angle to the shaft: this angle, of 15 degrees, is exactly a quarter the angle through which an ordinary hexagonal nut turns when it moves one flat. In a restricted area. therefore, the spanner needs to be turned only 30 degrees, removed from the hexagon, turned over and back through 30 degrees to hold the next flat. The next time it is turned over and moved back 30 degrees, the jaws take another hold on the same flats. This is repeated as often as necessary, with only a 30 degree turn required each time.

Ring spanner

While the open-ended spanner oilers accessibility. the ring spanner has the advantage of power and safely, since it holds all six points of the hexagon and will not slip if used properly. This type of spanner is sometimes called the 12-point spanner because the inside of the ring has 12 points, six of which fit around the points of the nut in one position and the other six of which come into operation when the spanner is repositioned on the nut. In this way the ring spanner can also be used to turn a nut or bolt with only a 30 degree movement. Ring spanners come in two designs: plain, where the spanner head is in the same plane as the shaft. and offset, where the head is set to one side of the shaft to give greater accessibility.

COMBINATION SPANNER

Although it is useful to have a set of both open-ended and ring spanners, the advantage of both types can be gained with a combination spanner. One end of the spanner is open and the other has a 12-point ring, as described earlier. The only disadvantage with this type of spanner is that more are needed to cover any given range of sizes since each spanner fits only one size of nut or bolt.

OBSTRUCTION SPANNER

This type of open-ended spanner is specially designed for use in restricted working conditions. It is shaped in such a way that it requires only a 17 degree movement to turn the nut or bolt. It is not normally bought in set form, but rather as a one-off purchase when needed to tackle a particular fastening problem.

BOX SPANNER

For nuts which are really deeply recessed, a box spanner is a most useful type to have; the inside of the head has only six sides and the whole of the working part fits around the hexagon. It does not have a fitted handle, but there are normally two holes in the tube at right-angles to each other which offera choice of levering positions when you insert a lever ; this turns the spanner.

While this type of spanner is comparatively inexpensive, it is not satisfactory for tough jobs.

SOCKET SPANNER

The socket spanner is undoubtedly the most versatile type, since it combines the strength and accessibility of the ring spanner and has a vast range of interchangeable components which can be fitted to it. The socket sizes come in metric, Imperial, Unified or American systems and the socket has a square hole in the opposite end to take the driving handle. The drive size most commonly used is ^in across the flats of the square, although I. f and I’m sizes are also available. The size depends on the size of the hexagon being turned and the £in accommodates most jobs likely to be tackled at home. TYPES OF DRIVER The most useful driver is the ratchet type with reversible setting; the number of ratchet stops is usually about 30, which means only about a 13 degree movement is needed to turn the hexagon of a nut or bolt.

Another driver is the sliding bar lever, which comprises a simple square that slides along a plain bar. Other drivers incorporate universal joints so the socket can be driven from almost any angle.

There is a universal joint attachment which fits behind the socket; this type is particularly useful when an extension bar is being used. Various lengths of extension bar are available, which can also be fitted end to end to suit the job in hand; each comprises a square at one end of a steel bar with a matching socket at the other end.

TORQUE WRENCH

The torque wrench is designed to accept sockets from a socket spanner set. It is fitted with a ratchet mechanism so the socket can be turned in either direction as necessary. The most important aspect of this type of wrench is that it incorporates a device which can be adjusted to control the torque or turning effort which is applied to the nut or bolt. TORQUE This is measured by multiplying the force applied to the spanner by the perpendicular distance between the point of application of the load and the centre of the nut or bolt. It is expressed in kilogram force centimetres or metres, pound force inches or feet or Newton metres. On vehicles, for example, almost all important bolted joints have to be tightened to a particular torque loading to avoid ovcrstressing.

WRENCH

The wrench key is used solely to tighten or undo hexagon socket screws which have a round head with a hexagonal hole in the centre; the mating hexagonal key fits into this hole. Hexagon socket screws are expensive, but they are often used on good quality machines because the head requires very little space and can often be sunk into a bored hole to prevent a protruding screw head. They can also be used to secure a neat joint in furniture which needs to be dismantled and reassembled easily. Hexagon socket grub screws, which have a pointed tip, are often used for fixing pulleys and collars on rotating shafts, such as in washing machines. A set of hexagonal keys is not expensive – and the keys are the only means of removing a hexagon socket screw without damaging the screw or the parts held together by the screw.

ADJUSTABLE SPANNER

The purist will only turn to the adjustable spanner when absolutely stuck for the correct tool. This type has adjustable jaws to fit any size of hexagon on a nut or bolt. Although well engineered, this spanner is still subject to wear and can slip if not used carefully, particularly when working on a tough job.

GIRDER SPANNER Although regarded as a last resort. there is one particularly useful small adjustable spanner – the girder spanner. Because of its size, it is used only on work which does not require much force to be moved, such as nuts on electrical terminals.

SELF-GRIP WRENCH

The self-grip wrench, which has a locking action, is one of the most useful hand-gripping tools. Once placed on the work, it can be locked in position and will stay there unsupported, allowing you the freedom to use both hands to manipulate the other parts of the job. This type of wrench is available with either fiat or rounded jaws with a variety of locking and release mechanisms, depending on individual manufacturers.

This type of wrench has a built-in mechanical advantage, so the gripping power is much greater than that obtained from ordinary pivot-type grips. This means care must be taken not to damage the workpicce.

PIPE WRENCH

This wrench, which has spring-loaded jaws, is adjustable to grip work of different sizes. The teeth on the jaws are designed to bite into the work-piece and the spring-loading ensures contact between the teeth and the work. This means it must only be used on work where slight damage will not matter. Once set. the pipe wrench can be used with a ratcheting action and very little angular movement. Its main use is on heavy pipe work, but it is not suitable for use on copper pipes.

CHAIN WRENCH

The chain wrench is similar in its gripping action to the pipe wrench, in that the teeth are angled to bile the work. The teeth are on the handle and a bicycle-type chain is wrapped round the work and fixed to the handle. This type of wrench has an advantage over the pipe wrench in as much as it does not have to be reversed on the work in order to turn the work in the opposite direction since there are two sets of jaws. one for turning forwards and one for turning backwards. A small adjustment of the hand position is sufficient to move from one set of jaws on the chain wrench to the other.

STRAP WRENCH

Sometimes you may want to turn a perfectly round object without scratching the surface. Here the strap wrench, which works on the same principle as the chain wrench, should be used. Instead of a chain and serrated jaws, this type has a strap of leather or nylon which grips the object on the principle of coil friction the harder the turning effort, the greater the gripping action, although at some point its effectiveness will be independent of the turning effort.

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