Chicago-Latrobe 47720 135 Degree Cobalt Jobber Drill Bit

135° Cobalt Jobber Drill Bit

The Chicago-Latrobe 47720 is a heavy-duty jobber length drill bit made from cobalt steel for drilling hard materials. Its 135 degree split point reduces walking and starts holes cleanly without a centre punch. The straw bronze finish identifies the cobalt alloy and resists wear. It suits maintenance, fabrication and automotive workshops that need reliable fractional inch tooling.

Heat resistance and cutting behaviour

Cobalt steel retains hardness at the elevated temperatures generated when drilling stainless steel, titanium and high-strength alloys. The 135 degree point geometry distributes cutting forces across two edges, lowering thrust requirement and reducing heat buildup in the workpiece. No coolant holes are present, so external lubrication or peck drilling manages chip evacuation and temperature in deep holes.

Replaces general-purpose high-speed steel bits

This bit upgrades from standard HSS jobbers when drilling work-hardening or abrasive metals that dull conventional edges quickly. The cobalt substrate extends edge life in materials that cause rapid flank wear on HSS. The jump is worth it for shops that regularly drill 5/16 inch holes in difficult alloys and need fewer bit changes per shift.