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1. Tool steel is sold in its annealed state,but if you are recycling a worn
tool the firststep is to anneal it. Heat to bright red and cool as
slowly as possible. Bury the hot steel in sand or ashes to achieve
a slow cooling. Another method is to heat in a kiln then leave the
steel in place to cool slowly
2. Shape the tool by forging, sawing,grinding and filing. Forging
must be done while the steel is red hot. Do not strike after the color
has gone or the steel may crack. When making a patterned tool such
as a stamp, the image is checked by pressing it into clay.
3. The tool is hardened by heating it to glowing red-orange and quenching
immediately in oil or brine. Small tools may be held in tweezers.
Large pieces are set on a brick or may be heated in a forge or furnace.
Punches are usually hardened only for the inch or two up from the
stamping end. |
The goal here is to convert the pearlite stage into
martensite. Because this phase is not magnetic, a magnet can be used
to confirm a high enough temperature. At proper temperature, a magnet
will not stick.
4. Check for hardness by stroking a file across the tool. It should
not cut in and should make a glassy sound.
5. Remove the gray oxide scale with fine sandpaper. This will allow
for better perception of colors in the next step.
6. Reduce brittleness by heating in a step called drawing the temper
(drawing; tempering). This can be done with a torch or, for small
pieces, on a hot plate. Go slowly, letting heat travel from a thick
section to a thinner one. The higher the temperature (longer heat)
the softer, more flexible the steel will become.
Testing Steel: Mild steel (also called low carbon steel) contains
.05 to .3% carbon. This amount is insufficient to cause hardening.
To test an unknown piece of material, hold it against a grinding wheel.
Tool steel throws bright white star-like sparks. Mild gives dull,
round orange sparks. |
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