The machinability of different aluminum casting alloys will vary widely. Raw castings often "gum" for lack of a better word, build-up on the edge of the tool, and make life miserable in general. What treatment (if any) are the castings recieving? Is the aluminum actually melting, or is the alloy too soft? When I did my own 356 castings, if I didn't heat treat them and artificially age, they would machine like the cheapest aluminum garbage you'd find in a hardware store. After treatment, the chip formation was vastly improved. The chips would come off in a brilliant shower and the finish was excellent.
I think the advise to speed things up and get adequate loading of the tool is sound. Carbide at high RPM and aggressive feed has always worked well for me. |