408 TRANSACTIONS OF THE AMERICAN INSTITUTE- 



told him that for nice work the tools should be left as the ham- 

 mer leaves them. One half of the instruments from the manu- 

 facturer will break if put to the test ; and he had for a long time 

 made his own tools. With regard to tempering, the old plan was 

 to make scythes and axes with a thick edge, leaving the farmers 

 to grind them down, because they could not temper the sharp 

 edges without burning. Fifteen years ago, in a file-shop in South 

 Boston, he noticed some files apparently prepared for tempering, 

 ■which looked as if they had been whitewashed. Going home 

 with that idea, he coated some small instruments with the flour 

 of pumice, and found that thus prepared the most attenuated 

 points could be tempered without burning. A file is made hard . 

 throughout, without injuring the tooth. 



Mr. Dibben said that there was another important fact with 

 regard to refining steel by the hammer ; that to make a good 

 cutting edge, after hammering the steel, it should never be 

 heated to so high a temperature again. In tempering a drill, 

 the point should not be heated, but only the shank. Hammering 

 hardens the steel ; but if you afterwards heat it and temper it in 

 the usual way, it will be the same steel that it was before.ham- 

 merin<^. There is iron that is absolutely drill proof. Some of the 

 Franklinite iron has such a peculiar hardness, and such a pecu- 

 liar structure, that it will destroy a drill which will pass through 

 any ordinary hardened steel. No drill he had ever seen, would 

 pass half an inch through Franklinite iron in an hour. 



Mr, Bliss. — I am aware that we have to heat steel higher in 



tempering, than we do in working it, but if properly prepared it 



endures it and still retains its value for cutting purposes ; but in 



tempering it, a great deal of skill is required so as not to over- 



^heat, especially where the edges are thin. 



Mr. Rowell, — What kind of fire do you use in tempering tools ? 



Mr. Bliss. — I have used the blaze of alcohol, of oil, and various 



other substances, and tempered in wax, tallow, salt water, and 



various other things. I have not been able to demonstrate clearly 



which plan is the best. 



Mr. Harrison. — A plan used more than any of these, is to heat 

 a pot of lead red hot. so that articles can be put in it and heated 

 to -just the temperature that is required. All that is necessary 

 is to plunge the article into it, and shake it about a few times, 

 and then put it into cold water, to harden it as we want it. 



