Glen Rosenthal, age 13, of Ruthland, Vt., for his question:
HOW IS THE KNIFE BLADE MADE SO STRONG?
The knife is probably the most useful of all the common tools used by man. The blade is made strong by first heating it and then putting it through a process called tempering.
Blades of expensive pocket knives are made of steel hammered into shape, or forged, by hand. The blades are made from strips of steel which come in the right width and thickness from the steel mills. The blade is shaped roughly with a hammer.
The blade is hardened by bringing it to a red heat and then dipping it suddenly in cold water. Now the hardened blade must be tempered.
Tempering toughens the blade, which is slightly brittle in its early state. The degree of toughness depends on the temperature to which the blade is heated. This temperature can be determined by the color of the steel. Steel heated to a red brown color has a higher degree of temper than steel heated to straw color.
After the desired temper has been reached, the steel may be cooled quickly or slowly, as only the heating affects temper.
The tempered blade is then sent to the grinder where a grindstone is used to sharpen it. A final finish is given the blade after it is fitted to the handle.
Expensive table knives are hand forged from a fine grade of steel called shear steel. Cheaper table knives are forged by a machine called a goff hammer. These knives are made of cast steel which is more brittle than shear steel.
Table knives in the United States are mostly manufactured by machinery rather than by hand.
In medicine, special knives called scalpels are important tools for surgeons. The blades here are made with the highest quality of tempered steel.
The knife was one of the first tools developed by the cave man. He sharpened and ground thin pieces of flint and quartz to make knives for skinning animals and cutting meat.
Knives can be dangerous as well as useful. Children and adults should always use great care when handling knives. They should never be stored within reach of young children and should always be kept covered or sheathed when not in use.
It is important that you never hand a person a knife with the point facing toward him.
Because of the danger of knives, many states have laws that prohibit a person from carrying a knife of more than a certain length.
A short bladed sword is called a dagger. It has a blade that may measure from six to 18 inches in length. It has a guard and a handle called a hilt.
Daggers are ordinarily worn at the belt and placed in a sheath or a scabbard. In Scotland, a dagger is called a dirk; in France it is called a poniard; and in Italy it is called a stiletto.
Pioneers in America carried a dagger called the bowie knife.