hammer(redirected from under the hammer)
Also found in: Dictionary, Thesaurus, Medical, Financial, Idioms.
a percussion machine for plastic deformation of metal ingots by means of the accumulated kinetic energy of its reciprocating parts. The hammer is one of the main machines in the forging and stamping industry; it is used in forging (forging hammers) and in closed-impression die forging and sheet-metal stamping (counterblow hammers).
Historical survey. Manually driven shaft hammers were known as early as the 13th and 14th centuries. Hammers driven by waterwheels, called center-strike hammers (in Germany), which were described by G. Agricola, and tail hammers (in France, Italy, and Great Britain), appeared in the early 16th century. Other types of hammers, such as face and drop hammers, became known later. In the mid-18th century, steam engines replaced waterwheels. In 1784, J. Watt proposed direct steam drive of the moving parts. However, it was only in 1842 that J. Nasmyth obtained a patent on the first steam hammer, which he designed and constructed.
Steam hammers and, to a lesser extent, pneumatic hammers became common before the end of the 19th century. In the 20th century, electric drive came to be used in various types of hammers. Explosive hammers appeared in the 1940’s in the USSR, and high-speed gas-driven hammers appeared in the 1950’s (at first in the USA and later in Europe).
Design and principle of operation. The main parts of a hammer are the moving or dropping parts, including the piston, piston rod, and ram; the anvil (the massive base); the frame, with rails for the moving parts; and the drive and control mechanisms. Smooth and notched heads and subpress dies are used for working ingots in forging hammers; dies are used in swage hammers. The upper head or upper portion of the die is attached to the ram, and the lower units are attached to the anvil. The billet is placed in the lower head or lower half of the die. Shaping of the article takes place upon impact of the moving part on the billet. The impact energy is absorbed by the anvil. The main parameters of a hammer, which determine its structural features and technological function, are the kinetic energy of the moving parts or the mass of the dropping parts.
Main types. The following hammers are distinguished according to their type of drive: steam-driven, pneumatic, and hydraulic hammers; high-speed gas-driven hammers, in which compressed gas is the working substance; hammers operating on the cycle of an internal-combustion engine (they are sometimes placed in the same category as gas-driven hammers), in which the energy of a mixture of gasoline vapors or gaseous fuel with air is used; explosive hammers; mechanical power hammers; and electromagnetic hammers.
The particular structural features of a hammer are dictated by the operations it performs. Thus, for operating convenience, the rail frame in forging hammers is removed from the hammer heads and not attached to the anvil. In swage anvil hammers, the anvil is connected to the rail frame, which provides precise control of the ram upon impact; in counterblow hammers, the anvil is replaced by a lower ram, and shaping of the billet takes place upon impact of the colliding rams. In explosive hammers, the anvil is replaced by a base to which a device for explosive forming is attached. In electromagnetic hammers, there is no die in the usual sense. Instead, an induction coil combines the functions of the equipment and the tool.
The most powerful die counterblow hammer, used in the USSR for producing forgings weighing up to 13 tons, has impact (dropping) parts with a total weight of 300 tons and an effective kinetic energy of about 1,570 kilojoules (kJ). The moving parts produce up to 30 impacts per minute, developing a relative velocity of 5–6 m/sec. High-speed hammers with effective kinetic energy of about 1,000 kJ develop a velocity of 12–20 m/sec.
REFERENCESFuchs, O. Molota. Leningrad-Moscow, 1932. (Translated from German.)
Zimin, A. I. Mashiny i avtomaty kuznechno-shtampovochnogo proizvodstva, part 1. Moscow, 1953.
Kuznechno-pressovye mashiny: Katalog-spravochnik, fascs. 1–4. Moscow, 1967–70.
Zhivov, L. I., and A. G. Ovchinnikov. Kuznechno-shtampovochnoe oborudovanie. Kiev, 1972.
A. F. NISTRATOV
What does it mean when you dream about a hammer?
Hammers suggest the power to forge new ways and build new dreams (e.g., as in the popular song “If I Had a Hammer”). A hammer can also indicate destructive force, as in hammering winds or hammering an opponent as well as an attempt to communicate a point, as in hammering away on some subject.
hammer(1) (HAMR) (Heat-Assisted Magnetic Recording) See HAMR.
(2) (Hammer) The code name for AMD's 64-bit CPU chips using 0.13 process technology. The Sledgehammer was introduced as the Opteron in 2003 for servers and workstations, and the Clawhammer began as the AMD Athlon 64. Designed for different markets, the Athlon 64 processor contained one HyperTransport link while the Opteron came with three.
Using silicon-on-insulator technology (SOI), the Athlon and Opteron versions of Hammer provide backward compatibility for all 32-bit software that has been running on PCs since the mid-1990s. In 2002, Microsoft announced Windows support for these 64-bit chips. See Opteron, Athlon, SOI and Itanium.
(3) In a printer, the mechanism that pushes the typeface onto the ribbon and paper or pushes the paper into the ribbon and typeface.