[Wastoute]

My recollection of historical progress was that somewhere around 1890 to 1900 was when machine tooling really began, and in some respects it was. I had thought that prior to that era even Colt SAA had to be assembled from parts that were hand forged into rough shape, filed, then hardened and ground into a final "Go-No Go" piece for assembly. Turns out early mills were around some 30 years or so before that so perhaps that 1860 to 1890 and the process of machining was really in evolution on conjunction with metallurgy to provide some steels for cutting and others for products.

I guess "W-group" tool steel was the first. I wonder if they even really knew why it was harder. Perhaps all they knew was "some ores produced harder steel" and they could use that for cutting softer steel. Then "high speed" steel in the 1910s really opened things up, and carbide in the 50s.