Dies for high pressure die casting (HPDC) has traditionally been manufactured by machining from slabs of tool steel. Currently, the possibility of manufacturing them using additive manufacturing is being explored. This provides some advantages such as the possibility of making conformal cooling channels. However, the size of the dies is often larger than can be handled in most metal printers Still, it is possible to partly print the die by adding cores with intricate conformal cooling on a traditionally manufactured die base. In this paper, a feasibility study of using selective laser melting (SLM) to print cores of maraging steel directly onto a die base is explored. Results shows that the strength of the bond between the two metals is sufficient, and that the connection between the drilled and printed tooling channels can be made. The paper reasons on the expected impacts on the tooling industry showing potential for extended die life and recovery of die bases via re-manufacturing.