Precision Twist Drill 5999078 Cobalt Jobber Drill Bit W

Product Description

The PRECISION TWIST DRILL 5999078 is a cobalt jobber-length drill bit sized to Letter W (0.3860 inches) with a 135-degree split-point geometry. The web-thinned, tapered-web construction reduces thrust at the point and improves chip evacuation. An oxide and straw coating provides surface hardness and mild lubricity for drilling into steel and other ferrous and non-ferrous materials. The straight cylindrical shank measures 0.3860 inches in diameter and 1.375 inches in length, fitting standard three-jaw drill chucks without adapters. This bit is designed for general-purpose heavy-duty production and maintenance drilling performed by machinists, pipefitters, ironworkers, and industrial maintenance technicians.

This drill bit is suited for use in ferrous steels, stainless steels, cast irons, non-ferrous metals, and high-temperature alloys, consistent with Primary Workpiece Material Codes P, M, K, N, and S. It fits bench drill presses, magnetic drill presses, CNC machining centers, and hand-held right-angle drills equipped with a chuck accepting a 0.3860-inch straight shank. The regular spiral flute with a 10xD flute-to-diameter ratio allows a maximum drilling depth of 3.750 inches, making this bit appropriate for through-holes and moderate-depth blind holes in structural steel, plate, pipe, and fabricated assemblies.

Key Features

• Cobalt high-speed steel construction for elevated heat resistance during continuous drilling in steel and alloys
• 135-degree split point with web thinning reduces walking and lowers required thrust force
• Oxide and straw coating provides surface hardness and mild corrosion resistance
• Regular spiral flute at 10xD ratio supports chip clearance to a maximum depth of 3.750 inches
• Straight cylindrical shank fits standard three-jaw chucks without requiring a reducer or adapter
• Meets ANSI and NAS 907 specifications for dimensional and performance consistency

Compatibility

Designed as a general-purpose jobber drill for use in right-hand rotating drill chucks across drill presses, CNC machining centers, and portable drills accepting a straight shank; part of the R10CO-R15CO-R18CO series from PRECISION TWIST DRILL.

Installation Notes

Installation is performed by machinists or qualified maintenance technicians using a keyed or keyless three-jaw chuck. Secure the shank fully into the chuck jaws before engaging the spindle. Use cutting fluid or coolant appropriate to the workpiece material to prolong cutting edge life; this bit does not support internal coolant-through delivery. Inspect the cutting edges and web for wear or chipping before each use and replace if edge integrity is compromised.