Chicago Latrobe 45638Chicago Latrobe HSS heavy duty jobber length drill bit set. Manufactured to NAS 907 Type B geometry aerospace specifications. Heavy-duty consruction for drilling in tougher materials. Manufactured from premium high-speed steel. 135 degree split point is self-centering for reduced thrust and easier penetration. Excellent choice for cutting stainless steel, tool steel, alloy steel, and cast iron. Black oxide surface treatment adds lubricity and wear resistance and adds lubricity to imrove chip flow.