Nickel, chromium, etc., are always given in per cent, as a 3.5 per cent nickel, which means exactly what it says—3½ parts in 100. Bearing this difference in mind all confusion will be avoided.
CLASSIFICATIONS OF STEEL
Among makers and sellers, carbon tool-steels are classed by "grade" and "temper." The word grade is qualified by many adjectives of more or less cryptic meaning, but in general they aim to denote the process and care with which the steel is made.
Temper of a steel refers to the carbon content. This should preferably be noted by "points," as just explained; but unfortunately, a 53-point steel (containing 0.53 per cent carbon) may locally be called something like "No. 3 temper."
A widely used method of classifying steels was originated by the Society of Automotive Engineers. Each specification is represented by a number of 4 digits, the first figure indicating the class, the second figure the approximate percentage of predominant alloying element, and the last two the average carbon content in points. Plain carbon steels are class 1, nickel steels are class 2, nickel-chromium steels are class 3, chromium steels are class 5, chromium-vanadium steels are class 6, and silico-manganese steels are class 9. Thus by this system, steel 2340 would be a 3 per cent nickel steel with 0.40 per cent carbon; or steel 1025 would be a 0.25 plain carbon steel.
Steel makers have no uniform classification for the various kinds of steel or steels used for different purposes. The following list shows the names used by some of the well-known makers:
| Air-hardening steel | Chrome-vanadium steel |
| Alloy steel | Circular saw plates |
| Automobile steel | Coal auger steel |
| Awl steel | Coal mining pick or cutter steel |
| Axe and hatchet steel | Coal wedge steel |
| Band knife steel | Cone steel |
| Band saw steel | Crucible cast steel |
| Butcher saw steel | Crucible machinery steel |
| Chisel steel | Cutlery steel |
| Chrome-nickel steel | Drawing die steel (Wortle) |
| Drill rod steel | Patent, bush or hammer steel |
| Facing and welding steel | Pick steel |
| Fork steel | Pivot steel |
| Gin saw steel | Plane bit steel |
| Granite wedge steel | Quarry steel |
| Gun barrel steel | Razor steel |
| Hack saw steel | Roll turning steel |
| High-speed tool steel | Saw steel |
| Hot-rolled sheet steel | Scythe steel |
| Lathe spindle steel | Shear knife steel |
| Lawn mower knife steel | Silico-manganese steel |
| Machine knife steel | Spindle steel |
| Magnet steel | Spring steel |
| Mining drill steel | Tool holder steel |
| Nail die shapes | Vanadium tool steel |
| Nickel-chrome steel | Vanadium-chrome steel |
| Paper knife steel | Wortle steel |
Passing to the tonnage specifications, the following table from Tiemann's excellent pocket book on "Iron and Steel," will give an approximate idea of the ordinary designations now in use: