ii6 MODERN BLACKSMITHING 



ANNEALING 



By gradually heating and cooling steel will be soft- 

 ened, brittleness reduced, and flexibility increased. In 

 this state steel is tough and easiest drilled or filed. 

 Tool steel is sometimes too hard to drill or file without 

 first annealing it; and the best way to do this is to 

 slowly heat to a red heat, then bury the steel in the 

 cinders and let it cool slowly. To heat and let the 

 steel cool exposed to the air will do no good, as it cools 

 off too quick, and when cool the steel is as hard as 

 ever. This is air temper. 



HOW TO REPAIR BROKEN COGS 



Cogs can be inserted in a cogwheel in different ways. 

 If the rim of the wheel is thick enough a cog can be 

 dovetailed in. That is, cut a slot in the rim from the 

 root of the cog down, this slot to be wider at the bot- 

 tom. Prepare a cog the exact size of the cogs, but just 

 as much deeper as the slot. Before you drive this cog 

 in, cut out a chip on each end of the slot, and when the 

 cog is driven in you can clinch the ends where you cut 

 out. This will make a strong cog, and if properly 

 made will never get loose. 



Another way: If the rim is thin, then make a cog 

 with a shank on, or a bolt cog. If the rim is wide 

 make two bolts. The cog can be either riveted or 

 fastened with nuts. If only one shank is made, the 

 same must be square up at the cog, or the cog will 



