Tool steel for punches

Dan Jones

I have slowly started experimenting with punches for matrices and with hardening tool steel; this is in addition to regularly using tool steel with my milling machine. I have come across a very machinable tool steel called O6 (trade name Graph-Mo). O6 is not common and much more expensive than O1, why use the stuff? Its machinability is about 125% compared to other high carbon tool steels. When I attempt a punch, it is noticeably easier to use than O1. Here are the main alloys:

C=1.45    Mn=1.0     Si=0.90   Mo=0.25

Of course, it is the carbon content that stands out; it is a tool steel that has excess carbon in the grain boundaries. This makes it exceptionally machinable and for hardening, the original supplier Latrobe Steel states “Graph-Mo tool steel can be hardened to over Rockwell 60 C from a relatively low hardening temperature, which minimizes size change and distortion during heat treatment”. It is worth trying out.

Ramiro Espinoza

Can you point to the supplier's website? 

BTW, there is already a thread to discuss different steels for punchcutting: http://typedrawers.com/discussion/2171/punchcutting-materials-steel