Hammer

• Ball-peen hammer,[9] or mechanic's hammer
• Boiler scaling hammer[9]
• Brass hammer, also known as non-sparking hammer or spark-proof hammer and used mainly in flammable areas like oil fields
• Bricklayer's hammer
• Carpenter's hammer (used for nailing), such as the framing hammer and the claw hammer, and pinhammers (ball-peen and cross-peen types)[9]
• Cow hammer – sometimes used for livestock slaughter, a practice now deprecated due to animal welfare objections[10]
• Cross-peen hammer,[9] having one round face and one wedge-peen face.
• Dead blow hammer delivers impact with very little recoil, often due to a hollow head filled with sand, lead shot or pellets
• Demolition hammer
• Drilling hammer – a short handled sledgehammer originally used for drilling in rock with a chisel. The name usually refers to a hammer with a 2-to-4-pound (0.91 to 1.81 kg) head and a 10-inch (250 mm) handle, also called a "single-jack" hammer because it was used by one person drilling, holding the chisel in one hand and the hammer in the other.[11] In modern usage, the term is mostly interchangeable with "engineer's hammer", although it can indicate a version with a slightly shorter handle.
• Engineer's hammer, a short-handled hammer, was originally an essential components of a railroad engineer's toolkit for working on steam locomotives.[12] Typical weight is 2–4 lbs (0.9–1.8 kg) with a 12–14-inch (30–35 cm) handle. Originally these were often cross-peen hammers, with one round face and one wedge-peen face, but in modern usage the term primarily refers to hammers with two round faces.
• Gavel, used by judges and presiding authorities to draw attention
• Geologist's hammer or rock pick
• Joiner's hammer, or Warrington hammer[9]
• Knife-edged hammer, its properties developed to aid a hammerer in the act of slicing whilst bludgeoning
• Lathe hammer (also known as a lath hammer, lathing hammer, or lathing hatchet), a tool used for cutting and nailing wood lath, which has a small hatchet blade on one side (with a small, lateral nick for pulling nails) and a hammer head on the other[13]
• Lump hammer, or club hammer
• Mallets, including versions made with hard rubber or rolled sheets of rawhide
• Railway track keying hammer[9]
• Magnetic double-head hammer
• Magnetic tack hammer
• Rock climbing hammer
• Rounding hammer, Blacksmith or farrier hammer. Round face generally for moving or drawing metal and flat for "planishing" or smoothing out the surface marks.
• Shingler's hammer
• Sledgehammer
• Soft-faced hammer
• Spiking hammer
• Splitting maul
• Strike Tack hammer
• Stonemason's hammer
• Tinner's hammer
• Upholstery hammer
• Welder's chipping hammer[9]

Steam hammer

Mechanically powered hammers often look quite different from the hand tools, but nevertheless, most of them work on the same principle. They include:

• Hammer drill, that combines a jackhammer-like mechanism with a drill
• High Frequency Impact Treatment hammer – for after-treatment of weld transitions
• Jackhammer
• Steam hammer
• Trip hammer
• Nail gun
• Staple gun

A hammer is a simple force amplifier that works by converting mechanical work into kinetic energy and back.

In the swing that precedes each blow, the hammer head stores a certain amount of kinetic energy—equal to the length D of the swing times the force f produced by the muscles of the arm and by gravity. When the hammer strikes, the head is stopped by an opposite force coming from the target, equal and opposite to the force applied by the head to the target. If the target is a hard and heavy object, or if it is resting on some sort of anvil, the head can travel only a very short distance d before stopping. Since the stopping force F times that distance must be equal to the head's kinetic energy, it follows that F is much greater than the original driving force f—roughly, by a factor D/d. In this way, great strength is not needed to produce a force strong enough to bend steel, or crack the hardest stone.

The amount of energy delivered to the target by the hammer-blow is equivalent to one half the mass of the head times the square of the head's speed at the time of impact ${\displaystyle (E={mv^{2} \over 2})}$. While the energy delivered to the target increases linearly with mass, it increases quadratically with the speed (see the effect of the handle, below). High tech titanium heads are lighter and allow for longer handles, thus increasing velocity and delivering the same energy with less arm fatigue than that of a heavier steel head hammer.[14] A titanium head has about 3% recoil energy and can result in greater efficiency and less fatigue when compared to a steel head with up to 30% recoil. Dead blow hammers use special rubber or steel shot to absorb recoil energy, rather than bouncing the hammer head after impact.

The handle of the hammer helps in several ways. It keeps the user's hands away from the point of impact. It provides a broad area that is better-suited for gripping by the hand. Most importantly, it allows the user to maximize the speed of the head on each blow. The primary constraint on additional handle length is the lack of space to swing the hammer. This is why sledgehammers, largely used in open spaces, can have handles that are much longer than a standard carpenter's hammer. The second most important constraint is more subtle. Even without considering the effects of fatigue, the longer the handle, the harder it is to guide the head of the hammer to its target at full speed.

Most designs are a compromise between practicality and energy efficiency. With too long a handle, the hammer is inefficient because it delivers force to the wrong place, off-target. With too short a handle, the hammer is inefficient because it does not deliver enough force, requiring more blows to complete a given task. Modifications have also been made with respect to the effect of the hammer on the user. Handles made of shock-absorbing materials or varying angles attempt to make it easier for the user to continue to wield this age-old device, even as nail guns and other powered drivers encroach on its traditional field of use.

As hammers must be used in many circumstances, where the position of the person using them cannot be taken for granted, trade-offs are made for the sake of practicality. In areas where one has plenty of room, a long handle with a heavy head (like a sledgehammer) can deliver the maximum amount of energy to the target. It is not practical to use such a large hammer for all tasks, however, and thus the overall design has been modified repeatedly to achieve the optimum utility in a wide variety of situations.

Gravity exerts a force on the hammer head. If hammering downwards, gravity increases the acceleration during the hammer stroke and increases the energy delivered with each blow. If hammering upwards, gravity reduces the acceleration during the hammer stroke and therefore reduces the energy delivered with each blow. Some hammering methods, such as traditional mechanical pile drivers, rely entirely on gravity for acceleration on the down stroke.