Negative‐Rake Milling

SOME truly remarkable results in high‐speed or “hyper” milling of steel forgings have been attained on a production basis at Eastern Aircraft's Linden, N. J., plant. To date, work has been confined to tough 4140 chrome‐molybdenum steel forgings; some annealed and some heat‐treated to 40–41 Rockwell C and 180,000 lb. per sq. in. tensile strength. Milling rates range from about five to nearly IS times those previously attained with conventional cutters run as fast as usual procedure dictated.