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A Hammer is a tool meant to deliver an impact to an object. The most common uses are for driving nails, fitting parts, forging metal and breaking up objects. Hammers are often designed for a specific purpose, and vary widely in their shape and structure. The usual features are a handle and a head, with most of the weight in the head. The basic design is hand-operated, but there are also many mechanically operated models for heavier uses.
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Types of Hammers
A wide range of Hammers are available, varying in shape, size and weight. The different styles reflect different uses.
The shape of Hammer heads has not changed much over the years although some modern materials are now used in both the head and handle. Traditionally handle were made of wood fixed through a hole in the head; this allowed the handle to be easily replaced if required. Modern hammers use modern materials and the handles are often built into the head - often with a form of built-in shock absorber to make them easier to use.
Claw Hammer
The most popular hammer for general work, available with a wooden (often hickory wood), fibreglass or steel handle; with or without rubber grip. The most popular weights are 455-680g (16 to 24oz). The claw is normally curved, and incorporates a 'V' cut-out to draw nails from timber. The claw can be used to lever up floorboards or where other places where a lever is required; care must be taken (especially with cheaper models) as the force applied can easily weaken the joint between the handle and the head.
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Ball Pein Hammer
Normally used by engineers, the pein in this case, is rounded and is usually used for shaping metal and closing rivets. Ball pein hammers are available from 55 - 1100 (4 oz up to 2 lb.), 110 - 165g (8oz 12oz) are the most suitable for general use. Handles are normally wood, usually Hickory or in some cases Ash.
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Cross and Straight Pein Hammer
Again, mainly used for shaping metal, the pein can be at right angles to the handle or parallel with it. The most useful domestically is the cross pein, where the pein can be used for starting panel pins and tacks. Handles are normally wood, usually Ash.
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Club Hammer
Sometimes called a Lump Hammer, it has a double faced head, and is useful for light demolition work, driving steel chisels and masonry nails. As debris is likely to fly, the wearing of safety glasses and working gloves is recommended. Weight 1135g (2 1/2 lb) being best suited to domestic work. Handles are normally wood, usually Hickory.
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Sledge Hammer
Used for the heavier jobs, such as driving in stakes or to break up concrete, stone or masonry. For lighter jobs just the weight of the head may be used for blows, but for heavier work, the hammer is swung like an axe. Wear suitable protective clothing, including safety glasses. Weights 6, 8, 10, 12 and 14 lb.
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Rubber Mallets
Various types are available, with hard and soft rubber, plastic or copper faces. Some come with a choice of faces which are interchangeable. Useful for striking materials such as chrome wing outs, where a steel face would cause damage. In some cases, can replace a mallet for cabinet work.
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Brick Hammer
These are specialist hammers developed to meet the needs of various trades. The Brick Hammer is used for striking a bolster or setting and cutting bricks, concrete blocks, tiles and stone. Wearing suitable protective clothing, including safety glasses is recommended while working.
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Scutch Hammer
Scutch hammer is described by its type: single scutch and double scutch. Similar in shape to the brick hammer. The single scutch hammer has one striking face like the brick hammer, while on the other end of the head a groove is cut to take either scutch combs or chisels. These bits are replaceable and are used for cutting stone or brickwork or for removing mortar from brickwork prior to re-pointing. The double scutch has no striking face, but is grooved at both ends.
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Hammer Manufacturing
Design
The two major components of a hammer are the head and the handle. The design of these two components depends on the specific application, but all hammers have many common features.
The striking surface of the head is called the face. It may be flat, called plain faced, or slightly convex, called bell faced. A bell-faced hammer is less likely to bend a nail if the nail is struck at an angle. Another face design is called a checkered face. It has crosshatched grooves cut into the surface to prevent the hammer from glancing off the nail head. Because it leaves a checkered impression on the wood, it is usually only found on framing hammers used for rough construction.
The surface of the head around the face is called the poll. The poll is connected to the main portion of the head by the slightly tapered neck. The hole where the handle fits into the head is called the adze (adz) eye. The side of the head next to the adze eye is called the cheek.
On the opposite end of the head, there may be a claw, a pick, a semi-spherical ball peen, or a tapered cross peen depending on the type of hammer. There may also be a second face, as in a double-faced sledge hammer.
Hammers are classified by the weight of the head and the length of the handle. The common curved claw hammer has a 7-20 oz (0.2-0.6 kg) head and a 12-13 in (30.5-33.0 cm) handle. A framing hammer, which normally drives much larger nails, has a 16-28 oz (0.5-0.8 kg) head and a 12-18 in (30.5-45.5 cm) handle.
Raw Materials
Hammer heads are made of high carbon, heat-treated steel for strength and durability. The heat treatment helps prevent chipping or cracking caused by repeated blows against other metal objects. Certain specialty hammers may have heads made of copper, brass, babbet metal, and other materials. Dead-blow hammers have a hollow head filled with small steel shot to give maximum impact with little or no rebound.
The handles may be made from wood, steel, or a composite material. Wood handles are usually made of straight-grained ash or hickory. These two woods have good cross-sectional strength, excellent durability, and a certain degree of resilience to absorb the shock of repeated blows. Steel handles are stronger and stiffer than wood, but they also transmit more shock to the user and are subject to rust. Composite handles may be made from fibreglass or graphite fibre-reinforced epoxy. These handles offer a blend of stiffness, light weight, and durability.
Steel and composite handles usually have a contoured grip made of a synthetic rubber or other elastomeric. Wood handles do not have a separate grip. Steel and composite handles may also be encased in a high-impact polycarbonate resin. The addition of this material around the handle increases shock absorption, improves chemical resistance, and offers protection against accidental overstrikes. An overstrike is when the hammer head misses the nail and the handle takes the impact instead. This is a common cause of handle failure.
There are several materials and methods used to attach the head to the handle. Wood handle hammers use a single thin wood wedge driven diagonally into the upper end
The head is made by a process called hot forging. A length of steel bar is heated to about 2,200-2,350° F (1,200-1,300° C) and then die cut in the shape of the hammer head. Once cut, the hammer head is heat treated to harden the steel. Of the handle, with two steel wedges driven through the wood wedge at right angles to secure it in place.
Manufacturing Process
The manufacturing process varies from one company to another depending on the company's production capacity and proprietary methods. Some companies make their own handles, while others purchase the handles from outside suppliers.
Here is a typical sequence of operations for making a claw hammer.
Forming the head
The head is made by a process called hot forging. A length of steel bar is heated to about 2,200-2,350° F (1,200-1,300° C). This may be done with open flame torches or by passing the bar through a high-power electrical induction coil.
The hot bar may then be cut into shorter lengths, called blanks, or it may be fed continuously into a hot forge. The bar or blanks are positioned between two formed cavities, called dies, within the forge. One die is held in a fixed position, and the other is attached to a movable ram. The ram forces the two dies together under great pressure, squeezing the hot steel into the shape of the two cavities. This process is repeated several times using different shaped dies to gradually form the hammer head. The forging process aligns the internal grain structure of the steel and provides much stronger and more durable piece.
During this process, some of the hot steel squeezes out around the edges of the die cavities to form flash which must be removed. As a final step the head is placed between two trimming dies, which are forced together to cut off any protruding flash. The head is then cooled, and any rough spots are ground smooth.
In order to prevent chipping and cracking of the hammer head in service, the face, poll, and claws are heat treated to harden them. This is done by heating those areas, either with a flame or an induction coil, and then quickly cooling them. This causes the steel near the surface to form a different grain structure that is much harder than the rest of the head.
The heads are cleaned with a stream of air containing small steel particles. This process is called shot blasting. The head may then be painted.
The face, poll, claws, and cheeks are polished smooth. This removes the paint in those areas. As part of this operation, the v-shaped slot in the claws is smoothed using an abrasive disc.
Forming the Handle
If the hammer has a wood handle, it is formed on a lathe. A piece of wood is cut to the desired length and secured at each end in the lathe. As the wood spins around the long axis of the handle, a cutting tool moves in and out rapidly to cut the handle profile. The position of the cutting tool is driven by a cam that has the same shape as the finished handle. As the cutting tool moves down the length of the handle, it follows the shape of the cam and cuts the handle to match it. The finished handle is clamped in a holding device and a slot is cut diagonally across the top of the handle. The handle is then sanded to give it a smooth surface.
If the hammer has a steel-core handle, the core is formed by heating a bar of steel, until it becomes plastic, and forcing it through an opening that has the desired cross-sectional shape. This process is called extrusion. If the hammer has a graphite fibre-reinforced core, the core is formed by gathering together a bundle of graphite fibres and pulling them through an opening that has the desired cross-sectional shape while epoxy resin is forced through the opening at the same time. This process is called pultrusion. In either case, the core may then have a protective plastic jacket moulded around it.
Assembling the hammer
If the hammer has a wood handle, the handle is inserted up through the adze eye of the head. A wood wedge is tapped down into the diagonal slot on the top of the handle to force the two halves outward to press against the head. This provides sufficient friction to hold the head on the handle. The wood wedge is secured in place with two smaller steel wedges driven through it crossways. The handle may then be stencilled with ink or labeled with an adhesive sticker to show the manufacturer, brand name, or other information.
If the hammer has a steel or graphite fibre-reinforced core, the handle is inserted up through the adze eye of the head. Liquid epoxy resin is then poured through the top of the hole to bond the handle in place. The handle is placed in a hollow die and a rubber grip is moulded around its lower portion. The handle may then be labeled with an adhesive sticker to show the manufacturer, brand name, or other information.
Hammer Geometry
This study examined the effect of hammer design parameters on task performance, operator physiological responses, perceived rate of exertion, task completion time, task accuracy, and user preference for hammering in the vertical (wall) and horizontal (bench) surface orientations. Two hammers used in the study differed with respect to their weight and softness of the handle grip. Ten male subjects participated in the laboratory experiment. The results showed that hammer design differences affect hammering task performance and perceived physical exertion. In general, the horizontally oriented hammering task was faster than vertically oriented hammering. However, task accuracy (i.e., number of nails hammered straight) was not statistically different with respect to either hammering orientation or hammer design. Subjects identified handle design, weight, and hammer mass distribution as critical factors that affect hammering task performance.
Using a Hammer
Hammers are basic tools but hammers are also notorious for causing thumb and finger injuries. It is estimated that some 50,000 Americans seek treatment every year as a result of a hammer injury. Here are some tips for using a hammer properly so that both you and the project you’re working on are kept safe from harm
• Check the hammer before use. Look for firm attachment of the head to the handle. Also check for splinters, loose wrapping, or other defects in the handle. If the hammer has any defects or is wobbly, do not use it. Not only will it require more energy to use but it is an accident waiting to happen.
• Get a firm grip on the handle. This will ensure that you don’t lose your hold on the hammer and have it flying out of your hand.
• Hold the hammer at the end of the handle. Beginners are often more comfortable holding the hammer handle midway. It is more energy efficient to grip the handle firmly at the end, but hold it a bit higher up while you are learning if that feels most comfortable and secure for you. With practice, you will become more proficient at holding the hammer towards the end, affording yourself more leverage.
• Hit your surface squarely with the hammer. Avoid banging a hammer sideways. Hit only with the head of the hammer and do not use the handle or the side of the hammer.
• Use your whole arm and elbow. As well as maintaining a good grip, it is important to rely on the strength of your whole arm and elbow and not just rely on your wrist and hand to pound the hammer with. Most importantly, keep a straight wrist and allow the weight of the hammer itself to do the pounding, not your arm.
• Place your work against a hard surface. Do not try to do hammering work on carpet or other soft surfaces, since it requires more energy.
• Work in a natural position. Beginners, children and the less proficient should hammer at waist height for the greatest ease. If you cannot move your work, keep your position as neutral and as natural as you can.
• Check before you swing. Keep your workspace clear of other objects and check that nobody is standing behind you or too near you when you use the hammer. You need plenty of space to swing the hammer without catching your arm or the hammer on another person or object.
• Practice. Good hammering technique comes from trial and error. You will develop your own technique over time that feels the most comfortable and works best for your projects.
Hammer Performance
For novices, hammer handles bent at 20 and 40 deg a study showed there was less total ulnar deviation than straight hammers. However, there was a trade-off in beginning and ending positions of the wrist in that the angled hammers reduced ulnar deviation at the impact position but increased radial deviation at the starting position of a hammer stroke. Handle angle did not significantly affect hammering performance. Wrist motion was affected minimally by hammering orientation, but hammering performance was significantly worse in the wall orientation compared with the bench orientation. This research suggests that for novice users, hammers with handles bent in the range of 20 to 40 deg could possibly decrease the incidence of hand/wrist disorders caused by hammering.
Two of the most important parameters of flail hammers, their shape and material composition, heavily influence the efficiency, lifespan and price of hammers. Identifying the best possible hammer, i.e., the design that provides the best results depends on the projected use and leads to the necessity of finding the best balance between these aspects.
In order to reach a good efficiency/life span ratio, technological solutions (steel quality, tempering process, etc.) have to be engaged, which can increase the price of the hammers. According to Digger’s experience, it is more effective to have high-quality hammers with an appropriate design than to use low-cost hammers that will be worn out in a few hours.
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