SCIENCE 
IS 
KNOWLEDGE. 
KNOWLEDGE 
IS 
POWER. 
A PRACTICAL JOURNAL OF 
HOME ARTS 
Vol. 11. 
NEW YOKK, SEPTEMBER, 1879. 
No. 9. 
Hardening and Tempering Steel Tools. 
HE following thor- 
oughly practical 
article on harden- 
ing and temper- 
ing steel tools, 
was contributed 
by Mr, Jas. Nas- 
myth to North- 
cott's work on 
*' Lathes." As it is 
especially suited 
for amateurs, we 
reproduce it : 
Whatever be the efficiency of the con- 
struction of a lathe, or other machine for 
cutting metal and other materials, the ex- 
cellence of the result must ultimately de- 
pend not only on the proper form of the 
tool w^hich operates on the work, but also 
on its capability to retain its cutting edge. 
This depends on the tool possessing the 
proper degree of hardness and temper. 
Before proceeding to the immediate sub- 
ject of these remarks, it may be as well to 
say a few words on the subject of the treat- 
ment of steel in forging it into the form of 
the tool required. In this respect, what- 
ever be the form of the tool, it is most im- 
portant for the preservation of the original 
good quality of the steel that, in forging 
it into the required form, the lowest de- 
gree of red heat should be given to the 
steel as may be consistent with its capa- 
bility to receive the desired form by the 
action of the hammer. Any degree of 
heat beyond that which is just visibly red 
in daylight, risks a permanent injury to 
the quality of the steel. 
In forging all such tools as are of a flat 
form, it is highly desirable that the finish- 
ing blows should be given on the flat, and 
not on the edge or sideways of the tool. At- 
tention to this apparently trifling observa- 
tion will be well rewarded by the enhanced 
durability of the tool so produced. 
In respect to " hardening " and tem- 
pering "of steel tools, they are two dis- 
tinct processes ; hardening first, tempering 
afterwards. The first induces the maxi- 
mum of hardness, accompanied by brittle- 
ness ; the second has reference to modify- 
ing that hardness, and so gaining in ex- 
change a certain degree of toughness. 
For the majority of tools employed in 
