Precision Twist Drill 5999044 Cobalt Jobber Drill Bit Letter N

Product Description

The PRECISION TWIST DRILL 5999044 is a cobalt jobber-length drill bit sized to letter N (0.3020 inches) with a 135-degree split-point angle. Built from cobalt high-speed steel and finished with a straw oxide coating, this bit is designed for heavy-duty drilling in ferrous and non-ferrous metals, stainless steel, and high-temperature alloys. The web-thinned, tapered-web construction reduces thrust at entry and improves chip evacuation. At 4.375 inches overall length with a 3.0625-inch flute, it handles deep-hole applications where standard HSS bits lose their edge. Licensed machinists, tool-and-die tradespeople, and industrial maintenance techs are the primary installers.

This bit is suited for production and maintenance drilling in steel, cast iron, aluminum, and similar workpiece materials coded P, M, K, N, and S per ISO material classification. The straight cylindrical shank fits standard three-jaw drill chucks without adapters. Its 10xD flute-to-diameter ratio makes it appropriate for deep through-holes in plate stock, structural members, and machined components where a shorter bit would bind or deflect. The regular spiral flute clears chips efficiently in both hand-fed and machine-fed setups.

Key Features

• Cobalt HSS construction for heat resistance and edge retention in hard metals
• 135-degree split-point angle reduces walking and lowers entry thrust
• Straw oxide coating provides mild lubricity and corrosion resistance
• Web-thinned tapered web improves chip clearance and cutting efficiency
• Right-hand, regular spiral flute for reliable chip evacuation in through-hole drilling
• Meets ANSI and NAS 907 standards for dimensional consistency

Compatibility

Part of the R10CO-R15CO-R18CO series. Designed as a general-purpose OEM-style replacement or direct-use cobalt jobber drill for applications requiring letter-N diameter drilling in steel and similar hard materials.

Installation Notes

Install in a three-jaw drill chuck or CNC spindle toolholder with the straight shank fully seated and the chuck tightened securely before starting the spindle. Verify drill press or machine spindle speed is appropriate for the workpiece material and bit diameter before drilling. Use cutting fluid or coolant on hard ferrous materials to extend tool life, even though this bit does not have internal coolant-through capability. Inspect the cutting edges for wear or chipping before each use and replace the bit if the point is damaged.