The steel should always be hardened on the rising heat, in general bringing the same slowly up to a dull cherry red, or to about 1450 degrees Fahrenheit, and then quenching in clear cold water, keeping the same in motion until the steel is cold. The temper should then be drawn according to the purpose of the tool, which could only be discussed for each particular case. The following range of temperatures are interesting, as being approximately indicated by the thin film of oxide tints which occur on the tool undergoing a tempering operation:
| Pale Yellow | 428 Degrees Fahrenheit |
| Golden Yellow | 469 Degrees Fahrenheit |
| Purple | 531 Degrees Fahrenheit |
| Bright Blue | 550 Degrees Fahrenheit |
| Dark Blue | 601 Degrees Fahrenheit |
CONCLUSION.
The effects of annealing, rolling, hammering, treating and tempering are best understood by those manufacturers who make a specialty of supplying a high grade tool steel, and in general it would be well if customers would consult freely with the producers of these steels, before attempting the delicate undertaking of Heat Treatment.
CHAPTER VI.
WHAT TOOL STEEL IS DOING TOWARDS WINNING THE WAR.
It hardly seems fitting that we should close these pages without giving our readers some little idea of just what the tool steel industry is doing for the successful conclusion of the great cause nearest our hearts.
One of the first statements which we could make would be that every metal worker in the world absolutely requires some form of tool steel or special alloy steel in the manufacture of his product. Of course, a very great many manufacturers other than the actual metal workers also need this same supply of tool steel in order that their production might not immediately cease. Volumes could be written on the vital importance of tools to industry in general, from the drills which drill out the hole in a hypodermic needle, to a twelve-ton drop-forge steam hammer. But for the present we may confine ourselves to simply the briefest mention of the vast number of iron and steel products actually and vitally engaged in the prosecution of the war.
We are told that we need ships, yet the ship industry could not proceed a day if its supply of necessary tools was cut off. The overwhelming increase in the manufacturing operations of the world which has taken place since the opening of the European War can better be imagined than explained, it being only necessary for us to point out here that the one absolute necessity which is common to all and required by all branches of such vast manufacture is the proper supply of necessary tools.
It has been the personal duty of the writer to make various visits to different Government shops and Arsenals as well as to the plants and shops of torpedo, shell and munition manufacturers and the vital part which the tools of production are playing in the great undertaking has been forcefully impressed upon his attention.