HEAT TREATMENT OF LATHE, PLANER AND SIMILAR TOOLS
Fire.—For these tools a good fire is one made of hard foundry coke, broken in small pieces, in an ordinary blacksmith forge with a few bricks laid over the top to form a hollow fire. The bricks should be thoroughly heated before tools are heated. Hard coal may be used very successfully in place of hard coke and will give a higher heat. It is very easy to give Blue Chip the proper heat if care is used in making up the fire.
Forging.—Heat slowly and uniformly to a good forging heat. Do not hammer the steel after it cools below a bright red. Avoid as much as possible heating the body of the tool, so as to retain the natural toughness in the neck of the tool.
Hardening.—Heat the point of the tool to an extreme white heat (about 2,200°F.) until the flux runs. This heat should be the highest possible short of melting the point. Care should be taken to confine the heat as near to the point as possible so as to leave the annealing and consequent toughness in the neck of the tool and where the tool is held in the tool post.
Cool in an air blast, the open air or in oil, depending upon the tools or the work they are to do.
For roughing tools temper need not be drawn except for work where the edge tends to crumble on account of being too hard.
For finishing tools draw the temper to suit the purpose for which they are to be used.
Grind thoroughly on dry wheel (or wet wheel if care is used to prevent checking).