Shrinking And Enlarging Work
: HARDENING CARBON STEEL FOR TOOLS
: The Working Of Steel
Steel can be shrunk or enlarged by proper heating and cooling.
Pins for forced fits can be enlarged several thousandths of an
inch by rapid heating to a dull red and quenching in water. The
theory is that the metal is expanded in heating and that the sudden
cooling sets the outer portion before the core can contract. In
dipping the piece is not held under water till cold but is dipped,
held a moment and removed. Then dipped again and again until cold.
Rings and drawing dies are also shrunk in a similar way. The rings
are slowly heated to a cherry red, slipped on a rod and rolled
in a shallow pan of water which cools only the outer edge. This
holds the outside while the inner heated portion is forced inward,
reducing the hole. This operation can be repeated a number of times
with considerable success.