Wrenches and Spanners
When screws or bolts with nuts were first developed in the fifteenth century, the box wrench was the most common tool used to work on them. The first: crews had square heads, something like modern carriage screws or lag bolts, but the more versatile hexagonal shape appeared quite early. By leaving one side of the "box" open the box wrench was adapted to work the hexagonal nut. The strength lost by-opening one end was compensated for by widening the jaws, and the resultant wrench could be used for both types of nut. The great variety of adjustable wrenches available at the present time are by-products of the intensive growth of machinery since the nineteenth century.
Old smith-made wrenches may be of wrought iron, and some are made of cast iron which is brittle and weak under tension.
Modern light duty wrenches, designed for use in awkward positions where their slenderness is essential, are stamped from sheet metal. The majority of engineering wrenches are forged from carbon steel or chrome vanadium.
Open Ended Wrench
OTHER NAMES: Open ended spanner, "C" spanner
SIZES: Various
MATERIAL: Alloy steel, wrought iron, cast iron
USE: To tighten or loosen nuts and bolts
One of the most common and versatile wrenches, the open ended wrench is designed to engage the nut or bolt head from the side. Although the open jaw is not as strong as the enclosed jaw of the box wrench, it is faster to work.
Open ended wrenches
The advantages of the open ended wrench is that it can be used where there is an obstruction directly above the nut, or on pipe unions where the pipe would restrict the use of a closed jaw wrench.
Make sure that the wrench fits snugly on the fiats of a nut; a slack fitting wrench will slip and round off the corners. Normally the head of an open wrench is set at an angle of 15° to the shaft. By turning the wrench over, another set of flats is engaged which is useful in a confined space.
OBSTRUCTION WRENCHES
Obstruction wrenches are special open ended wrenches intended to make working in confined spaces easier. They sometimes have curved shafts and the head can be set at an angle of up to 90°.
DOUBLE ENDED WRENCHES
Like most wrenches, open ended wrenches are often double ended. The ends are usually of consecutive sizes, each size being duplicated on one of the adjacent wrenches in the set. This allows you to work on a nut and bolt head which are the same size or to tighten two lock nuts simultaneously.
BICYCLE WRENCH
This is a multi-jawed wrench for work on the many different size nuts and bolts on a bicycle.
Box Wrench spanner
OTHER NAME: Ring spanner
SIZE: Various
MATERIAL: Steel
USE: To tighten or loosen nuts and bolts
The completely enclosed head of a box wrench is potentially stronger than any open wrench, but is slower in use as it must be engaged from above and carefully aligned before it will fit. Because the box wrench fits better, it is easier to strip a thread with it than with an open wrench. Moreover, it is also more likely to jam on a damaged nut.
The ring of the box wrench contains 6 or 12 points which locate on the flats of a nut. The 12 point wrench need only be turned 30° before engaging a new set of flats and is therefore preferable when working in confined spaces. Providing the fit is good, a 12 point wrench can be used on a square nut or bolt head.
The length of a box wrench varies in proportion to the size of the nut it is used on. This limits the amount of torque applied to smaller nuts.
A 12 point wrench can engage both hexagonal and square bolt heads.
OFFSET WRENCH
Most box wrenches are offset or cranked to give hand clearance, and to allow the operator to reach into recesses and over obstructions.
MULTIPLE BOX WRENCH
Intended for light work only, this is a light alloy wrench with a selection of different size "boxes" conveniently grouped together in one tool.
SPLIT BOX WRENCH
Unlike a standard box wrench, a split box wrench can be used on a pipe union where the pipe must pass through the jaws before they can engage the flats. It is no stronger than an open ended wrench but its better location makes it less likely to slip.
COMBINATION WRENCH
A combination wrench is open at one end and boxed at the other, both jaws being the same size. The greater strength of the box is used to loosen the nut, which can then be quickly removed with the faster, open ended jaw.
Adjustable Wrenches
Adjustable wrenches are usually open ended with one movable jaw. They are bulkier than equivalent fixed wrenches but will fit a wide range of sizes, being infinitely adjustable between limits and therefore not confined to a particular thread system.
Like open ended wrenches, adjustable wrenches have their heads set at an angle to the shaft, 15° and 90° being the most common setting, although 45° are also available.
There are several different patterns which vary according to their method of adjustment.
Slip Wrench
OTHER NAMES: Wedge spanner, shifting spanner
SIZE: Up to 30in.
MATERIAL: Steel, wrought iron
USE: To work nuts and bolts of any size between limits
The moving jaw of the slip wrench slides on the shaft and is held with a wedge which can be hammered tight. The tool is obsolete but still in use.
Monkey Wrench
OTHER NAMES: Screw wrench, coach wrench, bolt clam
SIZE: 6 to 18in.
MATERIAL: Steel
USE: To work nuts and bolts of any size between limits
BACK RACK WRENCH
This is like the slip wrench but has a worm screw on the moving jaw which acts on a rack on the shaft.
CENTER SCREW WRENCH
These are also known as "King Dick" spanners, named after the original manufacturer. With this type of wrench, the moving jaw carries a threaded rod which passes through a trapped nut in the handle.
FRONT RACK WRENCH
These are the same as the back rack type but with the mechanism at the front.
FRONT SCREW WRENCH
These are like the centre screw "King Dick" type having a captive nut and screw, but set on one side.
Crescent Wrench
SIZE: Up to 24in.
MATERIAL: Steel
USE: To work nuts and bolts of any size between limits
The wrench is adjusted by a captive worm screw in the handle acting against a rack on the moving jaw. Another pattern is operated by a thumb slide, located in the handle to make adjustment easy.
Using adjustable wrenches
Adjustable wrenches are inherently weaker than their solid equivalents, therefore greater care must be exercised when you use them to avoid straining the jaws, or damaging the nut or your hand. Only use an adjustable wrench when it is impossible to use a fixed one. When undoing a nut, use the largest convenient wrench, but not an over-large one as the thread could be stripped.
When fitting a wrench, make sure that the nut goes as far into the jaws as possible to prevent the, tool springing off. Close the jaws onto the nut, rocking the tool slightly to help tighten the wrench.
Unlike pipe wrenches, adjustable wrenches are intended for use in both directions. The jaws on some wrenches are set at an angle of 15° to the shaft. By turning the wrench over you can engage die same flats on the nut for a further turn.
Points of torque reaction
The black markers show where torque reaction occurs when the wrench is pulled clockwise. The brown markers show where it occurs when the wrench is pulled anti-clockwise.
Maintenance
Clean adjustable wrenches after use with a rag soaked in kerosene to remove grease. Lightly oil moving parts occasionally.
Multi-Purpose Wrench
OTHER NAME: Multi-plier
SIZE: 8in.
MATERIAL: Steel
USE: To provide the facility of wrench, pliers, screwdriver and wirecutters within a limited capacity
Grabber Wrench
SIZE: Jaw capacity: up to 5/8in.
MATERIAL: Alloy steel
USE: To work nuts and bolts of any size between limits
Unlike the normal adjustable wrench, this tool actually tightens as more force is applied to it, in much the same way as a pipe wrench.
Adjustable Box Wrench
OTHER NAME: Adjustable ring spanner
SIZE: Across flats: 3/8 to 7/8in.
Handle: 8-1/2in.
MATERIAL: Steel
USE: To work nuts and bolts of any size between limits
This automatically fits different size nuts and bolts and tightens as force is applied. It grips a minimum of three flats and need not be removed between strokes.
Tubular Box Wrench
OTHER NAME: Box spanner
SIZE: Various
MATERIAL: Steel
USE: To work nuts and bolts
Most tubular box wrenches are made from metal tubing and are double ended, with different sizes at each end. There are also single ended solid wrenches which look like socket extensions. Lengthen a tubular box wrench by fitting a socket or open wrench to the other end.
A tubular box wrench engages the nut from above, and although not as strong as a socket wrench, it is slimmer and usually deeper. It can be spun tight with the fingers and final torque applied by a tommy bar passed through holes in the wrench. If you fit a long tommy bar, you can easily apply too much force.
This will normally bend a mild steel bar but it can cause the thin walls of the wrench to override the points of the nut. Too much force can also strip the thread or even twist the body of the wrench. If the bar is centreed it is less likely to bend.
Using the wrench
Spin the wrench finger tight. For more torque, use a tommy bar (above) centreed to avoid bending.
Extending the range
Add another tubular box wrench (top) a socket (centre) or an open wrench (bottom).
Socket Wrench
OTHER NAME: Socket spanner
SIZE: Square drive hole: 1/4in. 3/8in., 1/2in., 3/4in., 1in.; Socket end: Various
MATERIAL: Steel
ACCESSORIES: Universal joint, rigid "L" bar handle, sliding "T" bar handle, ratchet handle, speed handle or brace speeder, hinged handle, extension bar, flexible extension
USE: To work nuts and bolts
The socket wrench has a boss with a square hole into which various handles can be fitted to drive the wrench. Moreover, the internal depth of the socket is limited and it may not be usable where a bolt protrudes a long way out of a nut. Special deep sockets are available for lone bolts.
Socket wrench as box wrench
In its simplest form the wrench can be used as an offset box wrench.
Socket wrench limits
In the smaller sizes the boss diameter may restrict access to the nut or bolt.
RIGID "L" BAR
This is the simplest handle. It can be used with either the long or the short leg of the "L" inserted in the boss to provide more force or speed.
SLIDING "T" BAR HANDLE
This carries a sliding head with a square drive. The head usually has two spring-loaded balls, one to grip the tommy bar, the other the socket.
RATCHET HANDLE
This increases operating speed because the socket does not have to be removed from the nut between strokes. The action of the handle can be reversed either by turning the wrench over or by throwing a lever.
HINGED HANDLE
This can be used at right angles to loosen a nut, and then swung to a vertical position where it can be spun between fingers. It can also be used to reach over or under obstructions.
SPEED HANDLE
A speed brace is faster than a tommy bar and has less torque.
EXTENSION BAR
This is fitted to increase the reach of the socket. Common lengths are 5in. and 10in. It has a square drive at one end to fit the socket while the other end takes the drive of the various accessories.
UNIVERSAL JOINT
Fit a universal joint if there is misalignment between the socket and the extension bar.
FLEXIBLE EXTENSION
This is used in the same way as a universal joint to allow a nut to be worked at an angle.
Torque Wrench
SIZE: Specified as a "torque range" for a particular tool
MATERIAL: Steel
USE: To apply an accurate preset force to a nut or bolt
Wrenches with a built-in torque measuring device are very useful where one or more nuts or bolts must be tightened to a pre-determined, accurate tighthess, such as the cylinder head on a car engine which must be sealed to an equal pressure all around.
DEFLECTING BEAM WRENCH
This consists of a steel bar with a square drive, usually double ended, at right angles to the shaft. Attached at one end is a pointer which extends parallel to the shaft almost to the other end v.here it is read against a double ended torque scale. (The scale is double ended so that it can be read when the wrench is inverted or used on L/H nuts.) Beyond this is a handle. The bar bends in proportion to the torque being applied; since the pointer is not subject to this force it remains straight while the scale moves past it.
DIAL INDICATING WRENCH
With this wrench, the movement of the square drive is transmitted against spring Pressure to a dial. As in the case of the deflecting beam wrench the drive is double ended.
MICROMETER OR PRE-SET WRENCH
The micrometer differs from the other two in that it does not have to be read and can, therefore, be used in difficult positions or in poor light. It is pre-set to the required torque, normally by turning a shaft which compresses a spring in the hollow handle.
The spring resists the turning of the square drive until the set torque is reached. At this point the wrench 'breaks" or moves freely for a few degrees giving a loud click. The micrometer does not have to be reset for another application.
What is torque?
Torque is turning force, usually measured in ft lbs or kg m, that is the force used times the length of lever used to apply it. For example a 101b pull with a 2ft lever gives 20ft/lbs of torque.
IMPROVISED TORQUE WRENCH
In the absence of a torque wrench, you can improvise with a tommy bar of known length and a spring balance. If possible use a tommy bar of 1 ft. length to allow the torque to be read directly from the balance. If the bar is not a convenient length a correcting calculation will have to be made:
Reading on balance =
Required torque (ft/lbs) x 12
------------------------------------
Length of bar (in.)
Bar 10in.
Required torque 50ft/lbs
Reading on balance:
50x12
-------- =601bs.
10
Spark Plug Wrench
OTHER NAME; Spark plug spanner
SIZE: Single ended: 5/8in. across flats or 10mm thread diameter; Double ended: 13/16in. across flats or 14mm thread diameter
MATERIAL: Steel, alloy steel
USE: To remove and replace engine spark plugs
Common spark plug wrenches, whether single or double ended, have either a tommy bar which passes through a hole in the wrench, or a captive swivel handle which can be used in line or at right angles.
Special socket wrenches are available to fit spark plugs.
Spark plug socket wrench
These fit any of the accessories in the set. The wrench often has a rubber ring inside to grip and protect the insulator of the plug.
Capstan Wheel Nut Wrench
SIZE: Various
MATERIAL: Steel
USE: To tighten or loosen nuts and bolts, usually the wheel nuts of cars
In its simplest form, the capstan wheel nut wrench comprises two double ended socket wrenches welded together in the form of a cross.
There are more versatile versions with a central boss into which are plugged six different wrenches in the form of extension bars.
Setscrew Wrench
OTHER NAMES: Allen key, hex key, Bristol wrench, Torx wrench
SIZE: Up to 3/4in.
MATERIAL: Steel
USE. To engage and turn a machine screw
An "L" shaped hexagonal Allen key is used where the head of a bolt or machine screw is recessed in such a way that a conventional wrench cannot reach it. It fits into a hexagonal hole in the end of the screw. Either end of the key can be inserted into the screw to give greater reach and speed or greater torque.
Bristol (Torx) wrenches have splines (thin radial strips) instead of flats and are normally single ended. They are used with screws slotted to match the splines.
Pipe Wrenches
Although similar to adjustable wrenches, pipe wrenches are intended for gripping and turning round objects such as pipework or damaged nuts. They have serrated jaws designed to provide grip on a smooth surface.
Some wrenches have the serrations on each jaw angled in opposite directions to improve the grip as force is applied to the handle. Never use a pipe wrench on a good nut as the jaws will damage it. Always apply force in the direction of the opening of the jaws.
Footprint Wrench
OTHER NAME: Pipe tongs
SIZE: Length: up to 21in.; Jaw capacity: up to 4-1/2in.
MATERIAL: Steel
USE: To grip round work
The name derives from the original manufacturer. The wrench has two handles with several possible positions for the pivot to accommodate a range of pipe sizes. It is tightened by squeezing the handles together.
Stilson Wrench
SIZE: 3/4 to 8in.
MATERIAL: Steel with hardened steel jaws
USE: To grip round work
The Stilson wrench is adjusted by means of a trapped nut working on a screw on the moving or "hook jaw". Pull on the wrench handle so that it hinges about its pivot and grips more tightly. Too much pressure may crush the pipe.
Chain Wrench
SIZE: 1/8 to 12in.
MATERIAL: Steel with high tensile steel chain
USE: To grip round work
A chain wrench comprises one or more serrated jaws and a length of bicycle type chain attached at one end of the jaw. The chain is wrapped around the pipe and hooked onto the other end of the jaw. When the handle is pulled, the cam action of the jaw tightens the chain and increases the grip of the wrench on the pipe.
Strap Wrench
SIZE: Up to 12in.
MATERIAL: Handle: cast iron; Webbing: canvas
USE: To grip and turn round objects such as pipework where the finish is important
The strap wrench is a variation of the chain wrench, the chain being replaced by canvas webbing. There are no serrated jaws to damage the finish on something like chrome pipework. The strap is wrapped around the pipe and passed through a slot in the handle. The strap is pulled tight and friction on the pipe is increased by levering on the handle.
Crocodile Wrench
OTHER NAME: Bulldog wrench
SIZE: Jaw capacity: up to 3in.
MATERIAL: Steel
USE: To grip and turn pipework, or other round objects
The crocodile pipe wrench looks like a conventional open ended wrench, with one smooth and one serrated jaw. Unlike other pipe wrenches, it does not have movable parts.
The jaws are pressed firmly over the pipe and the wrench turned away from the serrated jaw. This jaw grips the work while the smooth jaw slips, forcing the pipe further into the tapering jaws.
Basin Wrench
SIZE: For fittings up to 2in. across
MATERIAL: Steel
USE: To work on fittings where an ordinary wrench will not reach
This type of wrench has a Stilson type head with a long handle at right angles to it. It is designed for use in confined spaces, to work on basin nuts, flush valves and ballcocks. The jaw is reversible so that it can be used both to tighten and loosen nuts.
Hook and Pin Spanners
OTHER NAME: Spanner wrench
SIZE: 4 to 10in.
MATERIAL: Steel
USE: To turn special nuts or plugs
Special nuts are often made without flats but with edge notches or holes. They are used in restricted spaces or on smooth surfaces. One of their important applications is in bicycle construction. These nuts need specially designed wrenches with either hooks or pins to engage and turn them.
These wrenches are one-directional and normally fit a particular nut, although there are adjustable hook spanners.
Face pin spanners
These are used to engage the drive holes in the face of threaded plugs. They usually have two pins and can be used in either direction.
Specialized nuts
Notched or holed nuts can only be worked with hook or pin spanners.
Nut Drivers
OTHER NAME: Long shank box spanner
SIZE: Length: 7 to 9-1/2in.; To fit nuts: 3/16 to 5/8in. and up to approximately 1in.
MATERIAL: Shank: alloy steel; Handle: plastic or wood
USE: To drive nuts in like a screwdriver
The nut driver is extensively used by electricians and electronics engineers to turn smaller nuts or self tapping screws rapidly. They can be held in the end of the driver making for easy location.
