All users of tool steels should carefully study the different qualities of the steels they handle. Different uses requires different kinds of steel for best results, and for the purpose of designating different steels some makers have adopted the two terms "temper," and "quality," to distinguish between them.
In this case temper refers to the amount of carbon which is combined with the iron to make the metal into a steel. The quality means the absence of phosphorous, sulphur and other impurities, these depending on the ores and the methods of treatment.
Steel makers have various ways of designating carbon steels for different purposes. Some of these systems involve the use of numbers, that of the Latrobe Steel Company being given herewith. It will be noted that the numbers are based on 20 points of carbon per unit. The names given the different tempers are also of interest. Other makers use different numbers.
The temper list follows:
| No. 3 | temper 0.60 to 0.69 per cent carbon |
| No. 3½ | temper 0.70 to 0.79 per cent carbon |
| No. 4 | temper 0.80 to 0.89 per cent carbon |
| No. 4½ | temper 0.90 to 0.99 pet cent carbon |
| No. 5 | temper 1.00 to 1.09 per cent carbon |
| No. 5½ | temper 1.10 to 1.19 per cent carbon |
| No. 6 | temper 1.20 to 1.29 per cent carbon |
| No. 6½ | temper 1.30 to 1.39 per cent carbon |
| No. 7 | temper 1.40 to 1.49 per cent carbon |
USES OF THE VARIOUS TEMPERS OF CARBON TOOL STEEL
Die Temper.—No. 3: All kinds of dies for deep stamping, pressing and drop forgings. Mining drills to harden only. Easily weldable.
Smiths' Tool Temper.—No. 3½: Large punches, minting and rivet dies, nailmakers' tools, hammers, hot and cold sets, snaps and boilermakers' tools, various smiths' tools, large shear blades, double-handed chisels, caulking tools, heading dies, masons' tools and tools for general welding purposes.
Shear Blade Temper.—No. 4: Punches, large taps, screwing dies, shear blades, table cutlery, circular and long saws, heading dies. Weldable.
General Purpose Temper.—No. 4½: Taps, small punches, screwing dies, sawwebs, needles, etc., and for all general purposes. Weldable.