Precision Twist Drill 5999048 Cobalt Jobber Drill Letter O

Product Description

The PRECISION TWIST DRILL 5999048 is a cobalt jobber-length drill bit sized at Letter O (0.3160 inches) with a 135-degree split-point geometry. It is web-thinned for easier penetration and reduced thrust on entry. The straw oxide finish provides mild lubricity and heat resistance during cutting. With a regular spiral flute, straight shank, and tapered web configuration, this bit is built for general-purpose drilling in steel, cast iron, non-ferrous alloys, and high-temp alloys. Overall length is 4.5 inches with a 3.1875-inch flute length. It is sized to NAS 907 and ANSI standards and weighs approximately 0.08 pounds. Licensed machinists, tool and die shops, and maintenance trades install and use this bit in standard drill presses, CNC machines, and hand drills.

The 5999048 is suited for production drilling and maintenance applications in metal fabrication, aerospace component work, and general machining environments. Its cobalt construction handles harder steels and work-hardening materials that would wear out standard high-speed steel bits quickly. The 135-degree point reduces walking on entry and is well-matched to interrupted cuts or drilling into curved surfaces. The straight cylindrical shank fits standard three-jaw chucks without modification. This bit belongs to the R10CO-R15CO-R18CO series, covering heavy-duty jobber drill applications across a range of letter sizes.

Key Features

• Cobalt construction rated for drilling steel, stainless, cast iron, non-ferrous alloys, and high-temp materials (Material Codes P, M, K, N, S)
• 135-degree split point with web thinning reduces thrust and prevents walking on entry
• Straw oxide finish adds lubricity and mild heat resistance
• Regular spiral flute with tapered web for efficient chip evacuation
• Straight cylindrical shank fits standard drill chucks without adapters
• Meets NAS 907 and ANSI standards for heavy-duty jobber drill geometry

Compatibility

Part of the PRECISION TWIST DRILL R10CO-R15CO-R18CO series. Designed as a direct-fit jobber drill for any application requiring a Letter O (0.3160-inch) diameter hole in standard three-jaw chuck tooling setups.

Installation Notes

Installation and use of this drill bit should be performed by machinists or qualified tradespeople familiar with proper speeds and feeds for cobalt tooling in the target workpiece material. Secure the straight shank fully in the chuck before operation and verify runout before drilling into finished workpieces. Do not exceed the bit's maximum drilling depth of 3.1875 inches without retracting to clear chips. Use cutting fluid appropriate for the workpiece material to extend tool life and improve hole finish.