Glowing hot hard turning - GIF

[carl blum]

Hi Gang:
At the factory I worked at they made needles for fuel injectors this way: heat treat the bar stock and turn the needle hard. The next step was finish grinding and assembly. Before we would soft turn the needles, pre-grind, heat treat then finish grind and assemble. More steps but the real risk was finish grinding soft parts and assembling them into injectors. They would work well enough for a while, then the tip would leak, BAD!
They would heat treat the bar stock vertically in furnaces made for helicopter blades.
Carl.