Micro 100 DR-312-2 5/16" Carbide Jobber Drill Bit 118 Deg

Micro 100 Carbide Jobber Drill Bit

The Micro 100 DR-312-2 is a 5/16 inch carbide jobber drill bit built for machining hard materials. Its conventional 118-degree point suits general-purpose drilling in steel, cast iron and non-ferrous alloys. The bright uncoated finish avoids coating buildup in abrasive or sticky workpieces. Machinists and maintenance technicians choose it when high-speed steel wears too quickly.

Jobber Length Practical Limits

Jobber length gives enough flute reach for holes up to roughly five diameters deep in a single pass. Beyond that depth chip evacuation suffers and the bit can wander without peck cycles or through-coolant. The conventional 118-degree point needs higher thrust than split-point designs and can walk on curved or hardened surfaces. No coolant-through hole means external flood or mist is required for deep cuts.

Upgrade From High-Speed Steel Bits

This carbide bit replaces high-speed steel jobbers when tool life or cutting speed is the bottleneck. The jump pays off in high-volume production, tough alloys or abrasive composites where HSS dulls in minutes. It is not for hand-held drilling, low-rigidity setups or interrupted cuts where carbide’s brittleness causes chipping. Buyers who need through-coolant delivery or a split-point for self-centering should select a different tool.