For light lathe work, high speed steel is used in the adjustable tool holder. The most common tool for doing heavy work is the round nose which is made from various size steel.
High speed tool steel is sold under many brands. The method of handling is about the same for all. However each manufacturer will give the method which is best for his particular make of steel. In forging high speed lathe tools, a furnace or clean fire with plenty of coke is used. The steel is heated to a bright red heat, holding the steel at this heat as nearly as possible when hammering. Forging at a low heat is liable to cause the steel to burst. When the tool is forged, it is laid in a dry place on the forge to cool. When hardening, the point of the tool is brought to a white welding heat, about 2,100° Fahr., and this is noticeable by the appearance of melted borax, forming on the nose. The tool is now held in a compressed air blast, or dipped into sperm, linseed or lard oil until cool.
Annealing High Speed Steel.
The process is the same as the one used for carbon steel, heating to a red heat and covering the piece with slacked lime until cold.
In cutting high speed tool steel, the bar may be nicked with the emery wheel, then broken.
In working tool steel or iron of any weight the blows of the hammer must be heavy. Light blows stretch the outer part of the metal and not the center. This is liable to fracture it. The blow must be heavy so as to penetrate thru the bar. A trip hammer of ordinary size run by a belt is a very economical tool for the school shop. It is inexpensive and can be used to advantage in drawing out large pieces of stock, especially tool steel.
Every pupil should have more or less practice in the handling of a trip or steam hammer.
