: FIG. 77.--Peg withdrawn after cooling to 670 deg.C.
(magnified 800 diameters). Just at this moment the lamination of
pearlite, which now occupied its original area, was taking place.
In some parts the lamination was perfect, in other parts the iron
and iron-carbide were still dissolved in each other.]

[Illustration: FIG. 78.--Any peg withdrawn after 670 deg.C. on cooling
(magnified 100 diameters).]

[Illustration: FIG. 79.--Structure of overheated steel before (left)
and after refining (right).]

CHAPTER IX

HARDENING CARBON STEEL FOR TOOLS

For years the toolmaker had full sway in regard to make of steel
wanted for shop tools, he generally made his own designs, hardened,
tempered, ground and usually set up the machine where it was to
be used and tested it.

Most of us remember the toolmaker during the sewing machine period
when interchangeable tools were beginning to find their way; rather
cautiously at first. The bicycle era was the real beginning of
tool making from a manufacturing standpoint, when interchangeable
tools for rapid production were called for and toolmakers were in
great demand. Even then, jigs, and fixtures were of the toolmaker's
own design, who practically built every part of it from start to
finish.

The old way, however, had to be changed. Instead of the toolmaker
starting his work from cutting off the stock in the old hack saw,
a place for cutting off stock was provided. If, for instance, a
forming tool was wanted, the toolmaker was given the master tool
to make while an apprentice roughed out the cutter. The toolmaker,
however, reserved the hardening process for himself. That was one
of the particular operations that the old toolmaker refused to
give up. It seemed preposterous to think for a minute that any
one else could possibly do that particular job without spoiling
the tools, or at least warp it out of shape (most of us did not
grind holes in cutters 15 to 20 years ago); or a hundred or more
things might happen unless the toolmaker did his own hardening
and tempering.

That so many remarkably good tools were made at that time is still
a wonder to many, when we consider that the large shop had from 30
to 40 different men, all using their own secret compounds, heating
to suit eyesight, no matter if the day was bright or dark, and then
tempering to color. But the day of the old toolmaker has changed.
Now a tool is designed by a tool designer, O.K.'d, and then a print
goes