Precision Twist Drill 5997845 Cobalt Jobber Drill No 8

Product Description

The PRECISION TWIST DRILL 5997845 is a No. 8 wire-size cobalt jobber-length drill bit built for production and maintenance drilling in steel and other demanding workpiece materials. It measures 0.1990 inches in diameter with a 135-degree split point and a web-thinned, tapered-web geometry that reduces entry force and centers the bit without a pilot hole. Overall length is 3.625 inches with a 2.4375-inch flute length. The straw oxide finish provides baseline lubricity and heat resistance. This is a two-flute, right-hand-cut tool ground to NAS 907 and ANSI standards, suited for machinists, maintenance technicians, and fabricators working in metal-cutting applications.

This cobalt jobber drill is intended for drilling steel, stainless, cast iron, nonferrous alloys, and high-temp alloys — workpiece material codes P, M, K, N, and S. The 12xD flute-to-diameter ratio and straight cylindrical shank make it compatible with standard drill chucks and collet holders on bench drills, drill presses, CNC machining centers, and hand-held power drills. It belongs to the R10CO-R15CO-R18CO series, which covers heavy-duty cobalt jobber drills in this size range. Typical applications include structural fabrication, machine shops, and field maintenance where higher heat resistance than standard HSS is required.

Key Features

• Cobalt high-speed steel construction resists heat buildup when drilling harder steels and alloys
• 135-degree split point with web thinning reduces thrust force and improves self-centering
• Straw oxide finish adds surface lubricity and corrosion resistance
• Right-hand spiral flute evacuates chips efficiently in through-hole and blind-hole drilling
• Straight cylindrical shank fits standard 3-jaw chucks and collet systems without an adapter
• Ground to NAS 907 and ANSI standards for dimensional consistency across the series

Compatibility

Part of the PRECISION TWIST DRILL R10CO-R15CO-R18CO cobalt jobber series. Fits any drill chuck or collet accepting a 0.1990-inch straight shank. Rated for workpiece material codes P, M, K, N, and S per the supplier specification.

Installation Notes

Secure the shank fully in the chuck and verify concentricity before drilling to minimize runout and premature wear. Use cutting fluid or coolant when drilling steel or stainless to extend tool life; coolant-through is not supported by this tool. Operate at manufacturer-recommended surface footage for cobalt tooling in the target material — excessive speed generates heat that degrades the cutting edge. Inspect the point for chipping or wear before each use and recondition on a drill grinder when required.