While not his first invention, the hammer – and, in particular, the hammer head – has helped man expand his universe like no other invention until the advent of the personal computer. Through the centuries the hammer head has kept up with the times, evolving from the Stone Age to the Bronze Age to the Iron Age and through the Industrial Revolution (the Steel Age) to encompass materials such as stainless steels, tool steels and nonferrous alloys. Without heat treating, however, today’s hammer head would be no more useful as a tool than the ones whose heads were made of stone.
Blacksmiths needed hammers to do their jobs. They were the first to put the iron hammer heads into charcoal fire boxes until they reached an even cherry-red glow and the immersed them in barrels of water while still red hot. Later, they found oil produced a better-performing and longer-lasting hammer. However, early hammer designs were only concerned with the mass and general shape of the hammer head. The modern hammer is highly developed and pays careful attention to a great many factors, including: the location of the hammer’s center or gravity, configuration and the type of heat treatment.
Many steel hammer heads rely on a hot-forging process in combination with precisely controlled tempering to produce a durable, high-performing product. The most important part of the manufacturing process is controlling the degree of hardness of the head. Most U.S.-made hammer heads are made from either high-carbon or high-alloy tool steels. Brass, bronze and copper-faced hammers are also popular. Less expensive hammers can be produced from cast steel but are generally not as durable.
Heat Treating is the Key
Hammer hardness is the most essential factor in determining hammer life. While the hammer head must be extremely hard and resistant to wear, the shank must be more ductile in order to absorb shock. For example, in the manufacture of crusher hammers, selective induction hardening is used to create a gradually varying hardness between the shank and the tip while avoiding abrupt hardness changes. In cross section, the hardness extends for the full depth instead of merely at the surface. Hammer hardness in this case is normally measured by Brinell testing. If it’s too hard, it becomes brittle and chips easily. Also, the eye of the hammer needs to be strong rather than hard. As such, the eye is normally softer. Nonferrous hammer heads are solution treated, quenched and age hardened. Stress relief and annealing are also done depending on the end-use application.
If you thought there were only a couple styles of hammer heads, think again. One major U.S. hammer manufacturer produces more than 250 types, sizes and materials for every conceivable trade and task.
The most popular hammer for general work is the claw hammer, which is available in weights from 16 to 24 ounces (455-680 grams). The claw is normally curved, and it incorporates a “V” cut-out to draw nails from timber. The next most popular hammer for general use is the ball-peen hammer, which is used to round or shape metal and for closing rivets. Ball-peen hammers are available up to 2 pounds (907 grams), with 8-12 ounces (227-340 grams) being the most common for general use.
The club hammer, or baby sledge, weighs 2.5 pounds (1,134 grams), has a double-faced head and is useful for light demolition work and for driving steel chisels and masonry nails. For heavier jobs, such as driving in stakes or to break up concrete, a sledgehammer with a weight of 7-14 pounds (3,175-6,350 grams) is often needed.
The hammers of tomorrow may involve more sophisticated materials, but heat treatment will always be a vital part of man’s next best friend.